tag:theconversation.com,2011:/africa/topics/brain-control-series-31489/articlesBrain Control series – The Conversation2016-09-29T20:08:14Ztag:theconversation.com,2011:article/638132016-09-29T20:08:14Z2016-09-29T20:08:14ZEveryone’s different: what parts of the brain make our personalities so unique?<figure><img src="https://images.theconversation.com/files/137686/original/image-20160914-4936-1ihm9d6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Because everyone is different, psychologists have long debated how to characterise personality.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/beautyisintheeye2/15521669960/in/photolist-pDABHj-aiFiJD-a1XehG-9xrJQt-m7QQgG-agE9Pa-fSXY5-e3eqvr-zbaYaW-gBGYH-7z3iQx-zBwUYH-5jufDb-7seAyF-arMviZ-5jpWYa-8SQ5hq-8FxQQ6-7fBZu1-7z75Dw-pbDV69-kJxsec-4YpHr-8mTCZ3-6AUXhm-7F568S-6Ny7sN-7F5671-5Ly6k3-95E8D5-bBtVH-8SQ4VA-9QCvzw-KG98y-298da-Cxriz1-e8gQ4i-eVnL3r-c5xdef-pkTRug-6HMM3q-CA5dY9-DxpS5N-DvgpUQ-A9xfhH-eiYwS6-8SQ4y5-f83g4R-8SLZP4-kJyHNW">Szoki Adams/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p><em>The brain is key to our existence, but there’s a long way to go before neuroscience can truly capture its staggering capacity. For now though, our <a href="https://theconversation.com/au/topics/brain-control-series-31489">Brain Control</a> series explores what we do know about the brain’s command of six central functions: <a href="https://theconversation.com/what-brain-regions-control-our-language-and-how-do-we-know-this-63318">language</a>, <a href="https://theconversation.com/the-emotion-centre-is-the-oldest-part-of-the-human-brain-why-is-mood-so-important-63324">mood</a>, <a href="https://theconversation.com/were-capable-of-infinite-memory-but-where-in-the-brain-is-it-stored-and-what-parts-help-retrieve-it-63386">memory</a>, <a href="https://theconversation.com/some-people-cant-see-but-still-think-they-can-heres-how-the-brain-controls-our-vision-63323">vision</a>, <a href="https://theconversation.com/how-our-brain-controls-movement-and-makes-new-connections-when-parts-are-damaged-63520">motor skills</a> and personality – and what happens when things go wrong.</em></p>
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<p>Personality is a broad term describing how people <a href="http://bjp.rcpsych.org/content/150/4/443">habitually relate to the world</a> and their inner self. After the developmental period through childhood and adolescence, these patterns of relating remain reasonably stable through life. They are then <a href="http://www.goodreads.com/book/show/1838804.Psychology">referred to as traits</a> and influence behaviour, thinking, motivation and emotion.</p>
<p>Since everyone is different in their own way, <a href="http://projects.ori.org/lrg/PDFs_papers/Goldberg.Am.Psych.1993.pdf">psychologists have debated</a> how to characterise personality. The most popular approach has so far been to <a href="http://www.annualreviews.org/doi/abs/10.1146/annurev.ps.41.020190.002221">use five dimensions</a>: openness to experience (curious or cautious), conscientiousness (organised or careless), extraversion (outgoing or solitary), agreeableness (friendly or detached) and neuroticism (nervous or secure). </p>
<p>A <a href="http://psycnet.apa.org/psycinfo/1992-25763-001">self-report questionnaire</a> is often used to give a score to each dimension, which then describes someone’s personality. These descriptions have been used to understand normal and abnormal behaviour, and to predict work success, academic achievement and interpersonal relationships. </p>
<p>Both genetic and environmental factors determine someone’s personality. Genes <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1399-0004.1994.tb04214.x/abstract">account for between 30-50%</a> of the determination and the rest is made up largely of environmental experiences unique to the individual. </p>
<h2>History of personality</h2>
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<a href="https://images.theconversation.com/files/139385/original/image-20160927-20144-15ztr1d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/139385/original/image-20160927-20144-15ztr1d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/139385/original/image-20160927-20144-15ztr1d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1369&fit=crop&dpr=1 600w, https://images.theconversation.com/files/139385/original/image-20160927-20144-15ztr1d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1369&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/139385/original/image-20160927-20144-15ztr1d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1369&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/139385/original/image-20160927-20144-15ztr1d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1720&fit=crop&dpr=1 754w, https://images.theconversation.com/files/139385/original/image-20160927-20144-15ztr1d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1720&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/139385/original/image-20160927-20144-15ztr1d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1720&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">An iron rod was driven through Gage’s head, destroying most of his left frontal lobe and resulting in a profound change in his personality.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Phineas_Gage_GageMillerPhoto2010-02-17_Unretouched_Color_CroppedEmphasizingIron.jpg">Wikimedia Commons</a></span>
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<p>Understanding the neurological physiology of personality is sometimes seen as the holy grail of psychology, and was the topic of Sigmund <a href="http://www.ebay.com.au/itm/like/122132968218?lpid=107&chn=ps">Freud’s first paper</a>, Project for a Scientific Psychology, in 1895.</p>
<p>Early developments in this field came from historical case descriptions. </p>
<p>The <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1114479/">classical case is of Phineas Gage</a> (1823-60), an American railroad worker who had a large iron rod driven completely through his head in an accident, which destroyed most of his left frontal lobe and resulted in a profound personality change. </p>
<p>After the accident, Gage was described as having become “fitful, irreverent, indulging at times in the grossest profanity (which was not previously his custom), manifesting… little deference for his fellows, impatient of restraint or advice when it conflicts with his desires.”</p>
<p>From this case, the frontal lobes, which occupy the front third of the brain, <a href="http://people.hss.caltech.edu/%7Esteve/files/grafman.pdf">emerged as the seat of higher functions</a> such as judgement, motivation, regulation of behaviour and social consciousness. </p>
<p>Later, in the early 20th century, neuroanatomists identified the limbic lobe – an arc-shaped part of the frontal, temporal and parietal lobes that sits in the middle of the brain – as the seat of emotion. It was recognised as <a href="http://www.springer.com/la/book/9783540346845">making an important contribution</a> to personality. </p>
<p>As our understanding evolved, personality has been regarded as a composite of character and temperament. </p>
<h2>Temperamental traits</h2>
<p>Temperament is understood as the way the body produces behaviour. It <a href="http://www.ncbi.nlm.nih.gov/pubmed/8038587">refers to certain biases</a> an individual has when responding to external stimuli.</p>
<p>A well-established model proposes that whereas personality traits are based on habitual behaviour, temperamental traits are <a href="http://www.lww.co.uk/kaplan-and-sadocks-comprehensive-textbook-of-psychiatry">someone’s predispositions</a> when it comes to four areas: harm avoidance, novelty seeking, reward dependence, and persistence. These are closely related to basic emotions such as fear, anger, attachment and ambition. </p>
<p>High harm-avoidance leads to avoiding behaviours that don’t produce reward or cause punishment; as in people who are shy, uncertain or socially inhibited.</p>
<p>Individuals with such traits have <a href="http://www.ncbi.nlm.nih.gov/pubmed/19904278">increased activity in the fear circuit of the brain</a>, involving the amygdala and other structures of the limbic lobe.</p>
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<a href="https://images.theconversation.com/files/139505/original/image-20160927-30419-1c3barj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/139505/original/image-20160927-30419-1c3barj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/139505/original/image-20160927-30419-1c3barj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/139505/original/image-20160927-30419-1c3barj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/139505/original/image-20160927-30419-1c3barj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/139505/original/image-20160927-30419-1c3barj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=504&fit=crop&dpr=1 754w, https://images.theconversation.com/files/139505/original/image-20160927-30419-1c3barj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=504&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/139505/original/image-20160927-30419-1c3barj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=504&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Individuals who are shy have high activity in the fear circuit of the brain.</span>
<span class="attribution"><span class="source">from shutterstock.com</span></span>
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<p>This activity has been linked to abnormalities in two neurotransmitters: serotonin and γ-amino butyric acid (GABA). Modulating these with drugs – such as selective serotonin reuptake inhibitors (SSRIs that include Prozac) and benzodiazepines, <a href="https://theconversation.com/weekly-dose-valium-the-safer-choice-that-led-to-dependence-and-addiction-59824">including Valium</a> – can help people with depressive, anxious and obsessive thoughts.</p>
<p>Novelty seeking leads to exploration and individuals high on this trait are curious, quick-tempered, impulsive and easily bored. They have <a href="http://www.nature.com/neuro/journal/v17/n8/full/nn.3743.html">increased activity in the basal ganglia</a>, which are clumps of neurons sitting in the middle of the brain. This trait has also been linked to the so-called pleasure molecule dopamine, which acts on the basal ganglia, and changes in this pathway are <a href="http://www.ncbi.nlm.nih.gov/pubmed/16715055">associated with seeking novelty in different ways</a>. </p>
<p>People with high reward dependence seek social rewards and are <a href="http://www.ncbi.nlm.nih.gov/pubmed/8038587">likely to be socially sensitive</a> and reliant on social approval. Those low on this trait are tough-minded, cold and aloof.</p>
<p>The temporal lobes of the brain play a major role in how we process social cues, and increased activity in the anterior part of these lobes and in a brain structure called the thalamus has been <a href="http://www.ncbi.nlm.nih.gov/pubmed/21126511">related to higher levels of reward</a> dependence.</p>
<p>Persistence leads to the maintenance of a behaviour despite fatigue, repetitiveness and frustration, and often results in such qualities as industriousness and determination. The regions of the brain particularly important for this include the inner and lower parts of the frontal lobes, <a href="http://www.ncbi.nlm.nih.gov/pubmed/21126511">especially those called the anterior cingulate and the orbitofrontal cortex</a>, and their networks that involve the basal ganglia.</p>
<p>Persistence is loosely related to motivation. Emotion plays a <a href="http://www.ncbi.nlm.nih.gov/pubmed/23329161">major role in maintaining this drive</a>, as basic emotions, such as happiness, tend to energise behaviour and lack of emotion has the opposite effect.</p>
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<img alt="" src="https://images.theconversation.com/files/139679/original/image-20160929-27026-18nqblu.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/139679/original/image-20160929-27026-18nqblu.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1153&fit=crop&dpr=1 600w, https://images.theconversation.com/files/139679/original/image-20160929-27026-18nqblu.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1153&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/139679/original/image-20160929-27026-18nqblu.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1153&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/139679/original/image-20160929-27026-18nqblu.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1449&fit=crop&dpr=1 754w, https://images.theconversation.com/files/139679/original/image-20160929-27026-18nqblu.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1449&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/139679/original/image-20160929-27026-18nqblu.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1449&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="attribution"><span class="source">The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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Read more:
<a href="https://theconversation.com/the-emotion-centre-is-the-oldest-part-of-the-human-brain-why-is-mood-so-important-63324">The emotion centre is the oldest part of the human brain: why is mood so important?</a>
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<p>Researchers have attempted to examine whether brains of high achieving people, such as Einstein, are different. While there <a href="http://www.ncbi.nlm.nih.gov/pubmed/23161163">have been reports</a> that brain regions involved in numerical and spatial abilities (mid-frontal and inferior parietal regions) were larger and the bundle of <a href="http://brain.oxfordjournals.org/content/early/2013/09/24/brain.awt252">fibres connecting the two halves of the brain</a> (corpus callosum) was thicker, <a href="http://www.bic.mni.mcgill.ca/users/elise/Alberts_brain.pdf">there is no consensus</a> that Einstein’s brain was remarkably different from others. </p>
<p>There is, however, considerable evidence that people with higher intelligence, as measured on psychometric tests, <a href="http://www.ncbi.nlm.nih.gov/pubmed/9246731">have larger brains on the average</a>. Geniuses whose brains have been studied and found to be large include Carl Gauss (mathematician), Rudolf Wagner (composer) and Vladimir Lenin (political leader), although there are also many exceptions to this rule.</p>
<h2>Character</h2>
<p>Character involves an individual’s goals and values in relation to oneself and others. It is the <a href="http://www.ncbi.nlm.nih.gov/pubmed/8038587">conceptual core of personality</a> and involves complex higher functions such as reasoning, abstraction, concept formation and interpretation of symbols.</p>
<p>A network involving the frontal, temporal and parietal lobes is <a href="http://www.cell.com/neuron/abstract/S0896-6273(15)00816-8">important for these functions</a>, with reasoning and abstraction being largely frontal lobe functions, symbolic representation served by the temporal and parietal lobes and formation of new memories facilitated by the hippocampus and the memory network. </p>
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<p>
<em>
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Read more:
<a href="https://theconversation.com/were-capable-of-infinite-memory-but-where-in-the-brain-is-it-stored-and-what-parts-help-retrieve-it-63386">We're capable of infinite memory, but where in the brain is it stored, and what parts help retrieve it?</a>
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<p>Interaction of these networks with regions regulating temperament and emotion leads to the emergence of individual personality. It is important to emphasise that no particular personality characteristic comes from a specific brain region, as the brain operates as a complex network. </p>
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<a href="https://images.theconversation.com/files/139507/original/image-20160928-30448-1xniwas.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/139507/original/image-20160928-30448-1xniwas.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/139507/original/image-20160928-30448-1xniwas.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=860&fit=crop&dpr=1 600w, https://images.theconversation.com/files/139507/original/image-20160928-30448-1xniwas.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=860&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/139507/original/image-20160928-30448-1xniwas.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=860&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/139507/original/image-20160928-30448-1xniwas.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1080&fit=crop&dpr=1 754w, https://images.theconversation.com/files/139507/original/image-20160928-30448-1xniwas.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1080&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/139507/original/image-20160928-30448-1xniwas.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1080&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">People suffering from dissociative identity disorder have been reported to have reduced volumes of the hippocampus and amygdala and reduced activity of the orbitofrontal cortex.</span>
<span class="attribution"><span class="source">from shutterstock.com</span></span>
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<p>There is also considerable redundancy in these networks, as they have an innate ability to compensate, <a href="http://www.normandoidge.com/?page_id=1259">sometimes referred to as neuroplasticity</a>. An excellent example of neuroplasticity was demonstrated in <a href="http://www.pnas.org/content/97/8/4398.full">London taxi drivers who were shown</a> to have increased grey matter in the back part of their hippocampi – related to spatial representation of the environment - when compared to those who weren’t professional drivers. </p>
<p>Neuroplasticity is <a href="http://www.ncbi.nlm.nih.gov/pubmed/12783955">instrumental in recovery from brain injury</a>, such as after a stroke, when other parts of the brain take over some of the functions of injured regions.</p>
<p>Not uncommonly, a problem in brain development or the failure of adaptive mechanisms leads to the development of personality disorder. This is when a person has an enduring pattern of behaviour and ways of thinking that deviates from social and cultural norms, causing distress. </p>
<p>Researchers have begun to look at the neurological biology of various personality disorders. One subject of interest has been multiple personality disorder, now referred to as dissociative identity disorder. People suffering from this have been reported to have <a href="http://www.ncbi.nlm.nih.gov/pubmed/16585437">reduced volumes of the hippocampus and amygdala</a> and reduced activity of the <a href="http://www.ncbi.nlm.nih.gov/pubmed/17961993">orbitofrontal cortex</a>. These have been linked to childhood trauma which results in abnormal regulation of emotion. </p>
<p>While we have come a long way from the days of phrenology, when personality was read by feeling bumps on the head, the neurological biology of normal and abnormal aspects of personality is only beginning to be understood. What is clear though, is that personality comes from a complex neural construct, shaped by genetics and early developmental experiences that influence the structure and function of the brain.</p>
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<p><em>Read the other articles on Brain Control <a href="https://theconversation.com/au/topics/brain-control-series-31489">here</a>.</em></p><img src="https://counter.theconversation.com/content/63813/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Perminder Sachdev receives funding from the National Health and Medical Research Council (NHMRC) and the Australian Research Council (ARC). He also has funding support from a number off oundations, including the Vincent Fairfax Foundation, the Holden Foundation, the Yulgilbar Foundation, and the Rebecca Cooper Foundation. </span></em></p>Both genetic and environmental factors determine someone’s personality. Genes account for between 30-50% of the determination and unique environmental experiences making up the rest.Perminder Sachdev, Scientia Professor of Neuropsychiatry, Centre for Healthy Brain Ageing (CHeBA), School of Psychiatry, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/635202016-09-28T20:09:51Z2016-09-28T20:09:51ZHow our brain controls movement and makes new connections when parts are damaged<figure><img src="https://images.theconversation.com/files/138926/original/image-20160923-25481-1k5lfk1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Our brain’s ability to strengthen or make new connections to adapt and change allows us to acquire new skills.</span> <span class="attribution"><span class="source">from shutterstock.com</span></span></figcaption></figure><p><em>The brain is key to our existence, but there’s a long way to go before neuroscience can truly capture its staggering capacity. For now though, our <a href="https://theconversation.com/au/topics/brain-control-series-31489">Brain Control</a> series explores what we do know about the brain’s command of six central functions: language, mood, memory, vision, personality and motor skills – and what happens when things go wrong.</em></p>
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<p>Having voluntary control over body movements is the only way we can interact with people, objects and our environment. Body movement is not just about controlling arms and legs; it’s also for our head and eyes to visually explore the world, for our facial expressions to show emotion, and for articulation of our lips, tongue and mouth to communicate. </p>
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<p><em><strong>Further reading:</strong> <a href="https://theconversation.com/what-brain-regions-control-our-language-and-how-do-we-know-this-63318">What brain regions control our language? And how do we know this?</a></em></p>
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<p>The devastating effects of the brain losing its ability to control body movements are seen in motor neuron disease – where progressive degeneration and muscle wasting leads to some patients becoming <a href="https://en.wikipedia.org/wiki/Locked-in_syndrome">“locked-in”</a>, meaning they can’t move or communicate in any way.</p>
<h2>The motor system and primary motor cortex</h2>
<p>The brain’s motor system is contained mostly in the frontal lobes. It starts with premotor areas, for planning and coordinating complex movements, and ends with the primary motor cortex, where the final output is sent down the spinal cord to cause contraction and movement of specific muscles. </p>
<p>The primary motor cortex on the left side of the brain controls movement of the right side of the body, and vice-versa, the right motor cortex controls movement of the left side of the body.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/132563/original/image-20160801-17037-tnbmxh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/132563/original/image-20160801-17037-tnbmxh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/132563/original/image-20160801-17037-tnbmxh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=598&fit=crop&dpr=1 600w, https://images.theconversation.com/files/132563/original/image-20160801-17037-tnbmxh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=598&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/132563/original/image-20160801-17037-tnbmxh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=598&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/132563/original/image-20160801-17037-tnbmxh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=751&fit=crop&dpr=1 754w, https://images.theconversation.com/files/132563/original/image-20160801-17037-tnbmxh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=751&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/132563/original/image-20160801-17037-tnbmxh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=751&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Different areas of the primary motor cortex connect to and control movement of different body parts.</span>
<span class="attribution"><a class="source" href="https://upload.wikimedia.org/wikipedia/commons/c/c4/1421_Sensory_Homunculus.jpg">Wikimedia Commons</a></span>
</figcaption>
</figure>
<p>Different areas of the primary motor cortex connect to, and control, movement of different parts of the body, forming a kind of body map known as the <a href="https://en.wikipedia.org/wiki/Cortical_homunculus">homunculus</a>. </p>
<p>The size of the area on the homunculus determines the level of fine movement control we have with that part of the body. So, for instance, a large proportion of the motor cortex is devoted to our thumb, fingers, mouth and lips, as they are vital for manipulating objects and speech articulation.</p>
<p>The connection from the primary motor cortex to muscles of the body is so important that any damage leads to an impaired ability to move. If someone suffers a stroke, for instance, that causes damage to the primary motor cortex on one side of their brain, <a href="https://en.wikipedia.org/wiki/Hemiparesis">they will develop an impaired ability</a> to move on the opposite side of their body. </p>
<hr>
<p><em><strong>Further reading:</strong> <a href="https://theconversation.com/some-people-cant-see-but-still-think-they-can-heres-how-the-brain-controls-our-vision-63323">Some people can’t see, but still think they can: here’s how the brain controls our vision</a>.</em></p>
<hr>
<p>If the area of damage is specific to only part of the primary motor cortex, such as the hand area of the homunculus, it will affect movements only of the corresponding part of their body, for example, the hand.</p>
<hr>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/139148/original/image-20160926-2470-1n9lfq1.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/139148/original/image-20160926-2470-1n9lfq1.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=542&fit=crop&dpr=1 600w, https://images.theconversation.com/files/139148/original/image-20160926-2470-1n9lfq1.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=542&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/139148/original/image-20160926-2470-1n9lfq1.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=542&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/139148/original/image-20160926-2470-1n9lfq1.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=681&fit=crop&dpr=1 754w, https://images.theconversation.com/files/139148/original/image-20160926-2470-1n9lfq1.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=681&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/139148/original/image-20160926-2470-1n9lfq1.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=681&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<hr>
<h2>Neuroplasticity and movement rehabilitation</h2>
<p>As with other parts of the brain, when neurons of the primary motor cortex are damaged they will never regrow or repair. However, the brain can heal itself and regain some lost function through <a href="https://youtu.be/ELpfYCZa87g">neuroplasticity</a>. This means undamaged parts <a href="http://science.sciencemag.org/content/272/5269/1791">can change their connections</a> and remap to other areas of the body to take over function, compensating for damaged parts of the motor cortex.</p>
<p>Neuroplasticity is the <a href="http://www.nature.com/nrneurol/journal/v7/n2/abs/nrneurol.2010.200.html">fundamental principle in physical rehabilitation</a>, such as physiotherapy for patients following stroke, that allows patients to regain motor function and recover. Through neuroplasticity, the more a particular movement is performed, the stronger the brain pathways for that movement become and the easier it gets to perform that movement in the future.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/138925/original/image-20160923-25499-ku4de6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/138925/original/image-20160923-25499-ku4de6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/138925/original/image-20160923-25499-ku4de6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/138925/original/image-20160923-25499-ku4de6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/138925/original/image-20160923-25499-ku4de6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/138925/original/image-20160923-25499-ku4de6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/138925/original/image-20160923-25499-ku4de6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Neuroplasticity is the fundamental principle in physical rehabilitation, such as physiotherapy, for patients following stroke.</span>
<span class="attribution"><span class="source">from shutterstock.com</span></span>
</figcaption>
</figure>
<p>Let’s look at an example of a stroke patient, Harry, who has problems with movement in his left leg. Harry might have altered patterns of walking due to damage in the leg area of the motor cortex of the right side of his brain. To help Harry regain efficient walking ability, the physiotherapist helps him perform sequences or patterns of walking by practising activation and control of specific muscle groups in his left leg. </p>
<hr>
<p><em><strong>Further reading:</strong> <a href="https://theconversation.com/were-capable-of-infinite-memory-but-where-in-the-brain-is-it-stored-and-what-parts-help-retrieve-it-63386">We’re capable of infinite memory, but where in the brain is it stored, and what parts help retrieve it?</a></em></p>
<hr>
<p>At first, Harry will need lots of concentration to use the correct muscles as his brain is laying down new neural pathways to compensate for the damaged areas. But as this practice is repeated and the new pathways are established and strengthened, correct movement becomes easier without much concentration. </p>
<p>This same principle of neuroplasticity also applies for learning in the healthy brain. Anytime we acquire a new skill such as learning to ride a bike, writing our signature or dancing the tango, it’s our brain’s ability to strengthen or make new connections to adapt and change that allows us to learn. </p>
<p>So if you are a ballet dancer or a gymnast, a swimmer or a soccer player, a watch-maker or micro-surgeon, your brain connections in your motor system will be different depending on the practice and skill you have with fine movement of different parts of your body.</p>
<p><em>This article was co-written with Zita Arends, who is a physiotherapist in stroke rehabilitation and aged care.</em></p>
<hr>
<p><em>Read other articles in our Brain Control series, <a href="https://theconversation.com/au/topics/brain-control-series-31489">here</a>.</em></p><img src="https://counter.theconversation.com/content/63520/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ross Cunnington receives funding from the Australian Research Council and the National Health and Medical Research Council</span></em></p>If you are a ballet dancer or gymnast, a watch-maker or surgeon, your brain connections in the motor system will differ depending on your skills for fine movements in different parts of your body.Ross Cunnington, Professor, Queensland Brain Institute, The University of QueenslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/633232016-09-27T19:22:33Z2016-09-27T19:22:33ZSome people can’t see, but still think they can: here’s how the brain controls our vision<figure><img src="https://images.theconversation.com/files/137028/original/image-20160908-25253-7xzbi3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The pathway from eye to brain begins in the retina, where light is converted into neuronal signals.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/devilnina/160297868/in/photolist-fayYm-boiRmn-3p1Z8-oSdm2-oSdzh-3p1Wc-613LZm-5pYF6w-fjp2og-oSdwa-fjD9A3-9hX2ZV-dtXRje-zmT6r-6bQ9sP-tkqNe-9b4699-ngg4KW-5GAcPb-jghQM-boiRqk-fjDcgy-5pAMnX-bojAci-5pAMs4-nvGhMS-9MrZ5-6UYkjt-r5Sp7Z-ptKX7X-8mgJiP-6UZ9hn-8mgxre-9TVnCo-ycDZxj-sjQbuw-oaoJUj-36Rve7-6V4bYN-8mjL8b-6V4C63-odVv78-7x5gKm-b8ChEx-8mjQQd-bpggrF-4EEpLe-nUWyh5-6V3Fej-neXU6b">nina/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p><em>The brain is key to our existence, but there’s a long way to go before neuroscience can truly capture its staggering capacity. For now though, our <a href="https://theconversation.com/au/topics/brain-control-series-31489">Brain Control</a> series explores what we do know about the brain’s command of six central functions: language, mood, memory, vision, personality and motor skills – and what happens when things go wrong.</em></p>
<hr>
<p>Mr B <a href="http://onlinelibrary.wiley.com/doi/10.1111/psyg.12064/abstract">presented to the emergency department</a> because of frequent falls and an inability to grasp anything in front of him. He could recognise his family by their voices but not by sight. When a pen was put in front of him, he claimed nothing was there, and he was unable to see the neurologist’s hands waving at him.</p>
<p>He was diagnosed with total blindness. However, Mr B was unaware of and unperturbed by his blindness. He vividly described surroundings that did not actually exist. Brain imaging revealed strokes that had damaged his visual cortex.</p>
<p>Mr B had a rare condition called <a href="http://onlinelibrary.wiley.com/doi/10.1111/psyg.12064/abstract">Anton’s syndrome</a>, characterised by denial of blindness. This is intriguing as it combines the most basic failure of visual perception (a complete loss of the ability to see) with a complete unawareness of this failure.</p>
<p>In this sense, it is one of the most dramatic illustrations of the consequences of damage to the brain’s visual system. </p>
<h2>The visual system</h2>
<p>The pathway from eye to brain begins in the retina, where light is converted into neuronal signals. Signals from the eye are transmitted, through a part of the <a href="http://www.news-medical.net/health/What-does-the-Thalamus-do.aspx">thalamus (which sits near the centre of the brain)</a> called the lateral geniculate body, to the primary visual cortex at the back of the brain. </p>
<p>The <a href="http://www.ncbi.nlm.nih.gov/pubmed/22715879">primary visual cortex</a> (shown in blue in figure ii below) is the first point at which visual signals reach the cortex – the sheet of wrinkly neural tissue that makes up the outer surface of the brain. The primary visual cortex can be thought of as a bottleneck through which all visual information must pass before it is distributed to other visual areas of the cortex.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/139134/original/image-20160926-13523-17pujyt.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/139134/original/image-20160926-13523-17pujyt.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/139134/original/image-20160926-13523-17pujyt.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=356&fit=crop&dpr=1 600w, https://images.theconversation.com/files/139134/original/image-20160926-13523-17pujyt.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=356&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/139134/original/image-20160926-13523-17pujyt.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=356&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/139134/original/image-20160926-13523-17pujyt.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=447&fit=crop&dpr=1 754w, https://images.theconversation.com/files/139134/original/image-20160926-13523-17pujyt.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=447&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/139134/original/image-20160926-13523-17pujyt.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=447&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Light arriving from the right visual field is processed in the left hemisphere of the brain and vice-versa.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The above figure shows how light arriving from the right visual field – that part of the world to the right of wherever we happen to be looking – lands on the left half of our retinas, the light sensitive part of the eye. </p>
<p>From there it is then transmitted to, and processed in, the left hemisphere of the brain. Conversely, light arriving from the left visual field is ultimately transmitted to and processed in the right hemisphere of the brain. This means damage to, say, the left primary visual cortex will result in blindness in the right visual field.</p>
<h2>Visual processing areas</h2>
<p>The visual areas beyond the primary visual cortex have different relative visual specialisations, such as for colour, motion, or face processing. As a rough rule of thumb, the further across the cortical surface a visual area is from primary visual cortex, the more complex the processing carried out by that area. </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/137124/original/image-20160909-13371-1qsgo9y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/137124/original/image-20160909-13371-1qsgo9y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/137124/original/image-20160909-13371-1qsgo9y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/137124/original/image-20160909-13371-1qsgo9y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/137124/original/image-20160909-13371-1qsgo9y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/137124/original/image-20160909-13371-1qsgo9y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/137124/original/image-20160909-13371-1qsgo9y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/137124/original/image-20160909-13371-1qsgo9y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Some neurons in the medial temporal lobe are responsible for the recognition of some faces, but not others.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/77494817@N08/6949342612/in/photolist-bA6crW-9Eq9ur-et2tUp-6ddyGj-3abWBC-avcGK5-awUnRj-4cuNLQ-9TbzLe-hCdXFY-dXNtih-ryEUWp-9Eq9fi-ePJaNa-zu29h8-a3WEaV-a3ZwdY-72ci6X-d8qJVh-d8qK2J-kk6sW-9QeEoH-c881L9-bV3e9C-f4iKF-9qKt7Y-5jSkw7-ryEUzx-rhdkBq-ryLLtp-ryEV1H-rwucTj-7VDWEb-8i38mT-9QhvxL-9tCLSs-9tCLNu-5jN578-5jSkXU-f4iHw-7PFEKq-bxBCrc-cpsgrJ-hroDg7-7LA9Zb-5K3dA3-aLYD3R-qgnCpm-45doL-49jYv4">shahanaj27/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>For instance, there are neurons in the medial temporal lobe – an area near the top of the visual pathway, at the interface between vision and memory – that appear to respond exclusively to particular faces. </p>
<p>As an example, one study reported encountering neurons that responded exclusively to pictures of <a href="http://www.nature.com/nature/journal/v435/n7045/abs/nature03687.html">Jennifer Aniston</a>’s face, but not to images of other people’s faces, of animals, or of prominent landmarks such as the Eiffel Tower. </p>
<p>Conversely, neurons in the primary visual cortex respond to much simpler attributes of visual images. They are sensitive to certain visual features, such as a small vertical edge at a particular location in the visual field, regardless of the object or scene giving rise to that edge – be it the edge of Jennifer Aniston’s face or the edge of a tree trunk or building.</p>
<p>A useful way of thinking about the organisation of visual areas is provided by the idea of two visual processing streams: <a href="http://www.scholarpedia.org/article/What_and_where_pathways">the dorsal and ventral visual pathways</a>. </p>
<h2>‘Where’ and ‘what’ we see</h2>
<p>The dorsal pathway extends from the primary visual cortex up into parietal areas, where bodily sensations such as touch are represented. This pathway is assumed to support the analysis of “where” things are located in space. </p>
<p>Lesions along the dorsal pathway can give rise to a range of deficits, such as <a href="http://www.ncbi.nlm.nih.gov/pubmed/24607223">optic ataxia</a>, where people cannot use visual information to accurately reach for and grasp objects; and <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3945799/#B24">oculomotor apraxia</a>, where people have reduced ability to voluntarily shift their gaze away from wherever they happen to be looking (sometimes called “sticky fixation”).</p>
<p>Other deficits resulting from dorsal pathway lesions are <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3627977/">simultanagnosia</a>, which is the inability to perceive more than one object at a time; and a complete lack of awareness of one half of the visual field, usually the left, known as <a href="http://jnnp.bmj.com/content/67/5/565.long">visual neglect</a>.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/137131/original/image-20160909-13348-1wl6n0i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/137131/original/image-20160909-13348-1wl6n0i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/137131/original/image-20160909-13348-1wl6n0i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=709&fit=crop&dpr=1 600w, https://images.theconversation.com/files/137131/original/image-20160909-13348-1wl6n0i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=709&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/137131/original/image-20160909-13348-1wl6n0i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=709&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/137131/original/image-20160909-13348-1wl6n0i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=891&fit=crop&dpr=1 754w, https://images.theconversation.com/files/137131/original/image-20160909-13348-1wl6n0i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=891&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/137131/original/image-20160909-13348-1wl6n0i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=891&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">In apperceptive agnosia, people wouldn’t be able to name a picture of an elephant, or to produce a copy drawing of one.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/hikingartist/8557161595/in/photolist-e3aG1T-ooa11x-8Xjh2K-fbHN5b-76xE3h-5TjMVw-bBjxMY-2An5iU-eEQSXp-dTeiek-fWu6qm-5D7meF-diu6nE-e3aG6M-tJoFi5-e3aG2H-99hZV7-kdLXAF-e1vqJG-7oxXAS-seCnVS-4BjEHU-5WgDTy-dVpBtJ-pJ7gw1-6wEcCG-ahFJUz-6yAd87-8CReUx-6nBr4-6wEdfw-6aa4fH-8tUbUr-cs7PHm-yLunY-8Xsc6U-kj9tmG-6wA7HV-o1CfZB-9ezxNp-5Ygctk-oHnf6X-rsjDS2-fntrCL-aZzVx8-8seaPv-bz64zw-xnozC7-cyaDq5-9CD6aN">Frits Ahlefeldt-Laurvig/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>The ventral pathway extends from the primary visual cortex down into the temporal lobe. This pathway supports analysis of “what” is seen, such as distinguishing whether we are looking at <a href="http://www.msn.com/en-my/video/lifestyle/letterman-trump-or-monkey/vp-BBncIJ8">Donald Trump or a monkey</a>. </p>
<p>Lesions occurring relatively early in the ventral pathway, in areas close to the primary visual cortex, can leave visual sensation intact but disrupt accurate processing of those sensations. </p>
<p>An example is <a href="http://link.springer.com/referenceworkentry/10.1007%2F978-0-387-79948-3_705">apperceptive agnosia</a>, in which patients have near normal acuity and sensitivity to light but are unable to accurately perceive visually presented stimuli. Such patients would, for instance, be unable to name an elephant that was shown to them, or produce a copy drawing of one.</p>
<p>Lesions occurring further along the ventral pathway can result in <a href="http://link.springer.com/referenceworkentry/10.1007%2F978-0-387-79948-3_708">associative visual agnosia</a>, in which patients have normal perceptual abilities (for instance, producing good copy drawings) yet are unable to demonstrate knowledge of objects they perceive accurately, such as what they are used for.</p>
<p>An interesting case of associative agnosia is provided by the <a href="http://europepmc.org/abstract/med/6505484">report of a farmer</a> who was no longer able to recognise previously familiar cows following ventral pathway damage. </p>
<p><a href="http://link.springer.com/referenceworkentry/10.1007/978-0-387-79948-3_852">Alexia</a>, an acquired disorder of reading in which people can accurately perceive written text but no longer extract meaning from it, can also be thought of as a form of visual associative agnosia.</p>
<p>While our knowledge of some of the basic mechanisms of visual processing has dramatically increased in recent times, we have a poorer understanding of how these processes are integrated into a larger whole. Many fascinating questions remain, such as how is it that individuals can exhibit complete unawareness of blindness as in Anton’s syndrome?</p>
<hr>
<p><em>Our previous articles in the series looked at how the brain <a href="https://theconversation.com/what-brain-regions-control-our-language-and-how-do-we-know-this-63318">produces and receives language</a>, how it <a href="https://theconversation.com/the-emotion-centre-is-the-oldest-part-of-the-human-brain-why-is-mood-so-important-63324">controls our mood</a>, and how it <a href="https://theconversation.com/were-capable-of-infinite-memory-but-where-in-the-brain-is-it-stored-and-what-parts-help-retrieve-it-63386">stores and retrieves memory</a>.</em></p><img src="https://counter.theconversation.com/content/63323/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chris Tailby receives funding from the National Health and Medical Research Council of Australia. </span></em></p>Light arriving from the right visual field is processed in the brain’s left hemisphere. So damage to the left part of the primary visual cortex will result in blindness in the right visual field.Chris Tailby, Head of Epilepsy Cognition Laboratory, Clinical Neuropsychologist, Florey Institute of Neuroscience and Mental HealthLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/633862016-09-26T19:46:48Z2016-09-26T19:46:48ZWe’re capable of infinite memory, but where in the brain is it stored, and what parts help retrieve it?<figure><img src="https://images.theconversation.com/files/137147/original/image-20160909-13356-s4zss0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Human memory is complex and neuroscientists are still trying to uncover the mechanisms that lead to memories being formed.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/28638567@N02/8596042964/in/photolist-7mTrqd-hB8JkA-bCk6mt-ai1bU3-76dmJJ-e6AY6j-5CViUx-3VY6Hx-7Wyh3R-4uzXT-dVUkBb-p86c2L-dP1VTK-cmB19o-b8Yt7T-iDaZy-cXaAR9-5DPsYo-oQBSvV-5CVBje-e8Hm7W-6KK3pU-oNkCVC-8HqqvS-9nHV9R-aUPRhe-6n5wz9-qGqRoi-bEMX1k-eXQnF2-nvAnBu-KWi7r-7qkFuJ-4ixHDo-qz3xtt-pdfTg5-cmAZY7-aNEToz-av1PqA-rvDdwv-awBQ3-rD94Y-e5Js9L-oQCutC-6y4ovK-9pg1f2-dtA3Hj-dSvv6w-6n1pmi-ouL1hi">Viki Reed/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p><em>The brain is key to our existence, but there’s a long way to go before neuroscience can truly capture its staggering capacity. For now though, our <a href="https://theconversation.com/au/topics/brain-control-series-31489">Brain Control</a> series explores what we do know about the brain’s command of six central functions: language, mood, memory, vision, personality and motor skills – and what happens when things go wrong.</em></p>
<hr>
<p>One of the critical functions of the brain is to encode and store information, which becomes our memories. Our memories provide us with insight into events and knowledge of the world around us and influence our actions and behaviours – forming important aspects of our personality. </p>
<p>There are multiple aspects and types of memories. What we usually think of as “memory” in daily usage is actually <a href="http://www.human-memory.net/types_long.html">long-term memory</a>. But there are also important <a href="http://www.human-memory.net/types_short.html">short-term</a> and sensory memory processes, which are required before a long-term memory can be established. </p>
<p>Memory is generally divided into two broad categories: <a href="http://www.brainhq.com/brain-resources/memory/types-of-memory/explicit-memory">explicit (declarative)</a> and <a href="http://www.brainhq.com/brain-resources/memory/types-of-memory/implicit-memory">implicit (non-declarative)</a> memory. </p>
<h2>Implicit memories</h2>
<p>Implicit, or non-declarative, memories are behaviours that we have learned, but cannot verbalise. These memories typically operate without conscious awareness, encompassing skills, habits and behaviours. </p>
<p>These behaviours run on auto-pilot – for example, tying your shoelaces. It’s easy to do once learned, but it is very difficult to tell someone how you perform this task. </p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/137149/original/image-20160909-13345-1p26ggz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/137149/original/image-20160909-13345-1p26ggz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=901&fit=crop&dpr=1 600w, https://images.theconversation.com/files/137149/original/image-20160909-13345-1p26ggz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=901&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/137149/original/image-20160909-13345-1p26ggz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=901&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/137149/original/image-20160909-13345-1p26ggz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1132&fit=crop&dpr=1 754w, https://images.theconversation.com/files/137149/original/image-20160909-13345-1p26ggz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1132&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/137149/original/image-20160909-13345-1p26ggz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1132&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Being able to tie your shoelaces is an implicit memory.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/vistavision/2529475927/in/photolist-4Rwe4V-573GUS-2yBHU-7cFJek-aY3XHP-9y3QJr-bKE51V-eJjEv8-5CzEJ6-6UPfZ3-8XncVY-7rCknH-d3vRF-6iQzgB-r6AWHA-jPZhxn-8cCDJA-8Xj9fR-dQUbRa-nZw5aN-hGNFi-dqHSSD-58GoTA-6bRKth-bDL26H-e6YeAo-qGGKcC-dyzdYq-Po1Hu-4SyQaw-iBoAtx-rqyWq8-5L8fRN-55KYx3-cnFH6s-6i3bGz-bmmSZF-pajhQv-6i3bCt-4oi5yu-hxERuM-8LT1DS-6i3bJa-6i7kC7-4G8qdj-dqHT1n-n2wkqU-7Y1X-diaCmJ-dyWDTC">vistavision/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Multiple areas of the brain form implicit memories as they involve a variety of responses to be co-ordinated. A key region of the brain called the <a href="https://www.britannica.com/science/basal-ganglion">basal ganglia</a> is involved in the formation of these “motor” programs. Additionally, the <a href="http://biology.about.com/od/anatomy/p/cerebellum.htm">cerebellum</a> at the back of the skull plays a vital role in the timing and execution of learned, skilled motor movement.</p>
<h2>Explicit memories</h2>
<p>Explicit, or declarative, memories can be verbally expressed. These include memories of facts and events, and spatial memories of locations. These memories can be consciously recalled and can be autobiographical – for instance, what you did for your last birthday – or conceptual, such as learning information for an exam. </p>
<p>These memories are easy to acquire. However, they are also easy to forget as they are susceptible to disruption during the process of forming and storing the information.</p>
<hr>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/138183/original/image-20160919-17012-aacmgl.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/138183/original/image-20160919-17012-aacmgl.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=500&fit=crop&dpr=1 600w, https://images.theconversation.com/files/138183/original/image-20160919-17012-aacmgl.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=500&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/138183/original/image-20160919-17012-aacmgl.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=500&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/138183/original/image-20160919-17012-aacmgl.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=629&fit=crop&dpr=1 754w, https://images.theconversation.com/files/138183/original/image-20160919-17012-aacmgl.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=629&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/138183/original/image-20160919-17012-aacmgl.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=629&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<hr>
<h2>Making long-term memories</h2>
<p>There are multiple stages to forming an enduring memory, and information can be lost (or forgotten) along the way. The <a href="http://www.simplypsychology.org/multi-store.html">multistore model of memory</a> proposes that long-term memories are made in three stages. Incoming information is transferred through sensory memory to short-term memory and then to long-term memory, rather than happening in one go.</p>
<p>The different types of memory each have their own particular mode of operation, but they all co-operate in the process of memorisation and can be seen as three necessary steps in forming a lasting memory.</p>
<p>The information encoded in each of these steps has its own duration. First, we must be paying attention to the information we are going to encode – this is sensory memory. Our attention switches all the time, so the incoming information is often fleeting – like a snapshot – but it contains details of sounds, sensations and images. </p>
<p>Short-term memory, or working memory, is stored for seconds to minutes, and has a very limited information capacity. Due to the limited capacity, working memory must “dump” information regularly. Unless this information is transferred to the long-term store it will be forgotten. </p>
<p>An example is being required to remember a phone number, which can be remembered for a short time, but is soon forgotten. But if this information is rehearsed by repetition, this information can pass into long-term memory, which has a seemingly infinite storage capacity. This means information can be accessed for a much longer duration. </p>
<p>Our long-term memories are the recollections of our lives. For example, that phone number might be linked to our family home and be remembered for years into the future.</p>
<p>Many areas of the brain play a role in the formation and storage of declarative memory, but the two main regions involved are the <a href="http://biology.about.com/od/anatomy/p/hippocampus.htm">hippocampus</a>, the emotion centre, and the <a href="http://www.wisegeek.org/what-is-the-prefrontal-cortex.htm">prefrontal cortex</a> at the very front of the brain.</p>
<hr>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/139130/original/image-20160926-13539-1kk7u0c.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/139130/original/image-20160926-13539-1kk7u0c.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1053&fit=crop&dpr=1 600w, https://images.theconversation.com/files/139130/original/image-20160926-13539-1kk7u0c.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1053&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/139130/original/image-20160926-13539-1kk7u0c.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1053&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/139130/original/image-20160926-13539-1kk7u0c.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1323&fit=crop&dpr=1 754w, https://images.theconversation.com/files/139130/original/image-20160926-13539-1kk7u0c.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1323&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/139130/original/image-20160926-13539-1kk7u0c.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1323&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<hr>
<h2>The prefrontal cortex and working memory</h2>
<p>The prefrontal cortex is important in the formation of short-term or working memory. Although these short-term memories are lost due to interference with new incoming information, they are essential for planning behaviours and deciding what actions to perform based on the current situation. </p>
<h2>The hippocampus and long-term memory</h2>
<p>A short-term memory can be consolidated into an enduring long-term memory. This involves a system of brain structures within the medial temporal lobe that are essential for forming declarative memories. The hippocampus is a key region in the medial temporal lobe, and processing information through the hippocampus is necessary for the short-term memory to be encoded into a long-term memory. </p>
<p>The long-term memory does not remain stored permanently in the hippocampus. These long-term memories are important and having them stored in only one brain location is risky – damage to that area would result in the loss of all of our memories. </p>
<p>Instead, it is proposed that long-term memories become integrated into the <a href="http://biology.about.com/od/anatomy/a/aa032505a.htm">cerebral cortex</a> (responsible for the higher order functions that make us human). This process is referred to as cortical integration; it protects the information stored in the brain.</p>
<p>However, damage to areas of the brain, particularly the hippocampus, results in loss of declarative memories, which is known as amnesia.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/137150/original/image-20160909-13342-nyh7m3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/137150/original/image-20160909-13342-nyh7m3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/137150/original/image-20160909-13342-nyh7m3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/137150/original/image-20160909-13342-nyh7m3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/137150/original/image-20160909-13342-nyh7m3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/137150/original/image-20160909-13342-nyh7m3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/137150/original/image-20160909-13342-nyh7m3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Rehearsing items of short-term memory can pass these into our long-term memory, which has a seemingly infinite capacity for storage.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/leonhg/411756099/in/photolist-ComK6-55mqTd-kKsfrs-9AeaM-79C5RF-6HR61p-bHnVHK-h1EWoa-sgf1QN-cZpXeW-8WJ2Jz-9eoN3H-eapEtU-9f63e-dR13gQ-NZ8dZ-nzQNg6-dQUtgK-2NvSxY-fj21jv-8rDRyQ-7dEb2J-aGsPSg-sfzGN-8XJZ3w-AcUdJ-uSdq8-CY1XW-h1EY3J-dR13jj-tYBDk-KXUWN-pYAekL-shCwP-6RHCKs-63V11-8WM5uL-YZAW-b9Wi3Z-dDYLoX-i69Xk-nWDbM-az25Q2-6EeFgC-h1A5Mz-32Ggf-KKxmt-GsXB-dRk545-32AUXJ">g_leon_h/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>The famous <a href="https://www.psychologytoday.com/blog/trouble-in-mind/201201/hm-the-man-no-memory">case study of “H.M.”</a> - Henry Molaison (born February 26, 1926, and died December 2, 2008) - demonstrated the hippocampus is vital to the formation of long-term memories. H.M. had his hippocampus removed as a 23-year-old in an attempt to treat epileptic seizures that originated in his <a href="http://science.sciencemag.org/content/253/5026/1380">medial temporal lobe</a>.</p>
<p>Removal of the temporal lobe, including the hippocampus, led to the inability to form new memories, known as anterograde amnesia. However H.M.’s short-term and procedural memory (knowing how to do things, like motor skills) remained intact, as did many of his memories before the surgery. </p>
<h2>The deteriorating brain</h2>
<p><a href="http://www.alz.org/alzheimers_disease_what_is_alzheimers.asp">Alzheimer’s disease</a> patients develop brain pathologies that damage neurons, particularly in the hippocampus. These are called <a href="http://thebrain.mcgill.ca/flash/d/d_08/d_08_cl/d_08_cl_alz/d_08_cl_alz.html">neurofibrillary tangles and amyloid-beta plaques</a>. Amyloid plaques disrupt communication between neurons. Neurofibrillary tangles damage the neuron’s transport system, killing the cells.</p>
<p>Damage to neurons in the hippocampus prevents the formation of new memories and also disrupts neurons that have formed networks encoding existing memories. This leads to the loss of these memories, called retrograde amnesia. </p>
<p>As the die-off of neurons increases, affected brain regions begin to shrink and waste away. By the final stages of Alzheimer’s, damage is widespread and much brain tissue is lost. </p>
<p>Functionally, Alzheimer’s disease patients lose more and more memories, including elements of language and important information about their lives. Procedural memories (motor skills) are the last ability to be destroyed. </p>
<p>Human memory is complex, and neuroscientists are still trying to uncover the mechanisms that lead to memories being formed. New scientific techniques are gradually allowing the examination of how memories are encoded and stored, but, as yet, the surface of the mind and the memories it contains have only just been examined.</p>
<hr>
<p><em>Yesterday’s articles looked at how the brain <a href="https://theconversation.com/what-brain-regions-control-our-language-and-how-do-we-know-this-63318">produces and receives language</a>, as well as how it <a href="https://theconversation.com/the-emotion-centre-is-the-oldest-part-of-the-human-brain-why-is-mood-so-important-63324">controls our mood</a>, enticing us to get up in the morning.</em></p><img src="https://counter.theconversation.com/content/63386/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Amy Reichelt receives funding from the Australian Research Council</span></em></p>Our memories provide us with insight into events, knowledge of the world around us and influence our actions and behaviours – forming important aspects of our personality.Amy Reichelt, Lecturer, ARC DECRA, RMIT UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/633242016-09-25T19:33:14Z2016-09-25T19:33:14ZThe emotion centre is the oldest part of the human brain: why is mood so important?<figure><img src="https://images.theconversation.com/files/137877/original/image-20160915-23120-g1xxy0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Our mood is a transient frame of mind that influences how we think and view the world. </span> <span class="attribution"><a class="source" href="https://unsplash.com/?photo=W5TJpNKI9c4">David Schap/Unsplash</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p><em>The brain is key to our existence, but there’s a long way to go before neuroscience can truly capture its staggering capacity. For now, though, our <a href="https://theconversation.com/au/topics/brain-control-series-31489">Brain Control series</a> explores what we do know about the brain’s command of six central functions: language, mood, memory, vision, personality and motor skills – and what happens when things go wrong.</em></p>
<hr>
<p>“<em>Somebody</em> woke up on the wrong side of bed this morning.” You know that comment; the one that rarely makes you feel any more gracious towards the world (or the person saying it). At other times you might feel particularly gracious and sunny, for no reason at all. </p>
<p>Our mood is a transient frame of mind that influences how we think and view the world. It is influenced by events in our lives, the amount of <a href="https://theconversation.com/chill-out-disturbed-sleep-plays-havoc-with-your-mood-and-mind-15994">sleep</a> we get, <a href="https://theconversation.com/chemical-messengers-how-hormones-affect-our-mood-42422">hormones</a>, even <a href="https://theconversation.com/here-comes-the-sun-how-the-weather-affects-our-mood-19183">the weather</a>. But what role does the brain play in shaping our mood?</p>
<h2>The limbic system</h2>
<p>Many regions fundamental to mood are buried deep in the most primordial parts of the brain; that is, they are thought to have been among the first to develop in the human species. This is probably because mood is evolutionarily important. </p>
<p>Being glum can be advantageous and has been shown to <a href="http://pss.sagepub.com/content/13/1/34.abstract">sharpen our eye for detail</a>, for instance. But, overall, the brain seems geared towards maintaining a <a href="http://www.ncbi.nlm.nih.gov/pubmed/25253069">mildly positive frame of mind</a>. Being in a good mood makes us more likely to seek new experiences, be creative, plan ahead, procreate and adapt to changing conditions.</p>
<p>The limbic system is the major primordial brain network underpinning mood. It’s a network of regions that work together to process and make sense of the world.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/138916/original/image-20160923-25468-13oswmr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/138916/original/image-20160923-25468-13oswmr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/138916/original/image-20160923-25468-13oswmr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/138916/original/image-20160923-25468-13oswmr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/138916/original/image-20160923-25468-13oswmr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/138916/original/image-20160923-25468-13oswmr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/138916/original/image-20160923-25468-13oswmr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">If you feel great, the hippocampus might guide you to walk down a path fringed with daffodils.</span>
<span class="attribution"><span class="source">from shutterstock.com</span></span>
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</figure>
<p>Neurotransmitters, such as serotonin and dopamine, are used as chemical messengers to send signals across the network. Brain regions receive these signals, which results in us recognising objects and situations, assigning them an emotional value to guide behaviour and making split-second risk/reward assessments.</p>
<p>The limbic system sits under the cerebrum (the largest and newest part of the brain) and is made up of structures such as the hypothalamus, hippocampus and the amygdala.</p>
<p>The almond-shaped <a href="http://www.sciencedirect.com/science/article/pii/S0896627305008238">amygdala</a> attaches emotional significance to events and memories. It came to the attention of emotion researchers in 1939 when monkeys whose amygdalae were removed <a href="http://www.nature.com/mp/journal/v6/n1/full/4000812a.html">showed bizarre patterns</a> of behaviour. They became fearless, hypersexual and either devoid of emotion or irrationally aggressive. </p>
<p>Dubbed Kluver-Bucy Syndrome, it is rare in humans, but has been observed in people with amygdala damage incurred, for instance, after a bout of brain inflammation.</p>
<p>The <a href="http://www.nature.com/neuro/journal/v7/n3/full/nn1190.html">hippocampus</a>, meanwhile, reminds us which courses of action are congruent with our mood. For instance, if you feel great you might like to walk down a path fringed with daffodils. If you feel crap, you may instead be drawn to that bar that spins melancholy albums by The Smiths. </p>
<p>The hippocampus has been <a href="https://theconversation.com/depression-damages-parts-of-the-brain-research-concludes-43915">shown to be shrunken</a> in people with chronic depression. This may account for common features of the condition, such as <a href="http://psycnet.apa.org/index.cfm?fa=search.displayRecord&uid=2006-23058-006">vague or non-specific recall</a> of personal memories.</p>
<p>The limbic system also regulates <a href="http://my.slc.edu/ICSFileServer/9fd1fc33-4c44-4830-af85-b9efc72b4a6f/bede258f-5443-47a2-96b3-b6ad68a46116/8bade204-0b95-444e-9a59-46320b312f17/ekman-levenson-friesen-83.pdf">biological functions</a> in line with our mood, such as accelerated heart rate and sweating triggered by feeling flustered. Being so old, however, the limbic system is rather primitive. In day-to-day life it’s controlled by some newer networks that co-ordinate how we think and act, so our behaviour is <a href="https://theconversation.com/why-you-shouldnt-want-to-always-be-happy-62086">conducive to achieving longer-term goals</a>, rather than always going wherever the mood takes us.</p>
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<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/138754/original/image-20160922-22540-3x9dov.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/138754/original/image-20160922-22540-3x9dov.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1172&fit=crop&dpr=1 600w, https://images.theconversation.com/files/138754/original/image-20160922-22540-3x9dov.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1172&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/138754/original/image-20160922-22540-3x9dov.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1172&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/138754/original/image-20160922-22540-3x9dov.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1473&fit=crop&dpr=1 754w, https://images.theconversation.com/files/138754/original/image-20160922-22540-3x9dov.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1473&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/138754/original/image-20160922-22540-3x9dov.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1473&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="attribution"><span class="source">The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<h2>Rival networks</h2>
<p>Researchers are increasingly looking towards newer networks to understand how the brain controls mood. Two particular networks that stand out across numerous studies are the autobiographic memory network and cognitive control network.</p>
<p>The autobiographic memory network processes information related to ourselves, including recalling personal memories and <a href="http://www.ncbi.nlm.nih.gov/pubmed/24502540">self-reflection</a>. Key <a href="http://psych.colorado.edu/%7Ehannaje/Publications_&_CV_files/Andrews-Hanna_Smallwood_Spreng_YCN_2014.pdf">hubs in this network</a> comprise brain areas inside the prefrontal cortex, which sits in the front of the brain; the hippocampus; the posterior cingulate cortex, which is the upper part of the limbic lobe; and parietal regions, which sit behind the frontal lobe and are important for mental imagery.</p>
<p>The cognitive control network links up regions that co-ordinate our attention and concentration so that we can <a href="http://www.sciencedirect.com/science/article/pii/S1364661313002222">complete tasks</a>. It recruits a circuit of <a href="http://link.springer.com/article/10.3758/s13415-011-0083-5">the front part of the cingulate cortex</a> and dorsolateral prefrontal cortex, which are specialised for cold, unemotional, rational thought.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/137166/original/image-20160909-13348-1eqn450.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/137166/original/image-20160909-13348-1eqn450.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/137166/original/image-20160909-13348-1eqn450.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/137166/original/image-20160909-13348-1eqn450.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/137166/original/image-20160909-13348-1eqn450.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/137166/original/image-20160909-13348-1eqn450.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/137166/original/image-20160909-13348-1eqn450.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">The autobiographic memory network switches on when someone is preoccupied by thoughts concerning themselves.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/james_sickmind/5448338716/in/photolist-9isahq-6Cbkrn-6ma21Z-51VtbF-6YUfab-9Bi5Nf-7LbZex-eoMgkT-dYye4K-noHe6D-cPCujs-7qYHVK-iiH6Rf-98Gx8P-5JrHG4-qhNVUY-8fwvFX-9xDSKk-2fPPTM-98KEQq-o692cA-8V1xZJ-dhqS4L-9V8r1T-fPfxTY-h9uur2-836bC9-btEDnt-aaXGYR-i2odhL-faYVrT-c2HwyN-5XcTmq-hsdayN-6enoYv-9Fq3PL-jcRtZ-4mG4eo-cmGtF5-aEiva9-7bM8aC-hLsNvB-HC2WHf-byGds7-4W6cGb-hLtAGJ-8SjP45-dSypEh-bWmQNf-ivTJJF">Mitya Ku/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>These two networks are thought to have a strained relationship. The autobiographic memory network switches on when someone is preoccupied by thoughts concerning themselves. This causes <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2850105/">the task-oriented cognitive control network to switch off</a>, thereby reducing our ability to complete whatever task we’re supposed to be doing. This is why daydreaming is frowned on at work. </p>
<p>Conversely, the autobiographic memory network is suppressed when the cognitive control network <a href="http://www.ncbi.nlm.nih.gov/pubmed/19913622">is required to gather the attention needed for a task at hand</a>. This is in line with the notion that we “lose ourselves” when we are absorbed doing something. </p>
<p>When the two networks don’t work properly, they can result in what psychiatrists refer to as <a href="https://theconversation.com/feeling-down-when-does-a-mood-become-a-disorder-14566">mood disorders</a>.</p>
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<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/138384/original/image-20160920-11095-6rb666.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/138384/original/image-20160920-11095-6rb666.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=427&fit=crop&dpr=1 600w, https://images.theconversation.com/files/138384/original/image-20160920-11095-6rb666.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=427&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/138384/original/image-20160920-11095-6rb666.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=427&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/138384/original/image-20160920-11095-6rb666.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=537&fit=crop&dpr=1 754w, https://images.theconversation.com/files/138384/original/image-20160920-11095-6rb666.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=537&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/138384/original/image-20160920-11095-6rb666.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=537&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="attribution"><span class="source">The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<h2>Mood disorders</h2>
<p>The <a href="https://theconversation.com/feeling-down-when-does-a-mood-become-a-disorder-14566">two major types</a> of mood disorders are depressive disorders, characterised by a persistent down mood, and bipolar disorders, expressed as extreme high or manic moods that alternate with periods of feeling down. </p>
<p>In depressive disorders, the autobiographic memory network gets <a href="http://www.ncbi.nlm.nih.gov/pubmed/26562681">stuck being on</a>. This leads to thinking-too-much-about-ourselves symptoms, such as brooding, rumination and self-loathing. The concurrent suppression of the <a href="http://www.ncbi.nlm.nih.gov/pubmed/26562681">cognitive control network</a> gives rise to symptoms such as poor concentration, indecisiveness and sluggish thinking.</p>
<p>Treatment for depressive disorders, such as <a href="https://www.cambridge.org/core/journals/psychological-medicine/article/neurobiological-mechanisms-of-repetitive-transcranial-magnetic-stimulation-of-the-dorsolateral-prefrontal-cortex-in-depression-a-systematic-review/859706D1B9CF90C267BE1D8348B832D9">transcranial magnetic stimulation</a>, involves stimulating the cognitive control network to work better. And medications aim to restore normal levels of <a href="https://www.youtube.com/watch?v=G4r3qCkLUDQ">neurochemicals</a> that communicate between the two networks and the limbic systems.</p>
<p>Many psychological therapies empower the sufferer to wrest control over their own mood. They often train the person to activate the cognitive control network, by challenging negative thoughts for instance, to strengthen it over time. They also seem to disrupt the domination of the autobiographic memory network through techniques such as mindfulness.</p>
<p>While trying to understand the neuroscience behind disordered mood is necessary, there is a push in psychology for mood investigations to focus more on the positives in everyone’s psychology; involving the fostering of <a href="http://www.blackdoginstitute.org.au/docs/Positivepsychology.pdf">resilience and our individual strengths</a>, for instance. </p>
<p>Much like the zeitgeist itself, however, investigations into the brain’s role in these functions are in their infancy.</p>
<hr>
<p><em>Want to know how the brain controls your language? Read today’s accompanying piece <a href="http://theconversation.com/what-brain-regions-control-our-language-and-how-do-we-know-all-of-this-63318">here</a>.</em></p><img src="https://counter.theconversation.com/content/63324/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Genevieve Rayner does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Many regions fundamental to mood are buried deep in the most primordial parts of the brain; that is, they are thought to have been among the first brain regions to develop in the human species.Genevieve Rayner, Postdoctoral Research Fellow, Florey Institute of Neuroscience and Mental HealthLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/633182016-09-25T19:32:58Z2016-09-25T19:32:58ZWhat brain regions control our language? And how do we know this?<figure><img src="https://images.theconversation.com/files/137024/original/image-20160908-25244-1zf7n8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Our language abilities are enabled by a co-ordinated network of brain regions that have evolved to give humans a sophisticated ability to communicate.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/homeofbastian/2830133659/in/photolist-5j6b8V-2YLMgN-fdTet2-7E3qmp-dPDTKu-FvFi2-3Z7wR-e77LXU-ezqVA5-dQJ17i-ae4PEz-efSzmw-3eVbfC-ksi7-7Yvcat-8uRQV3-4QjLhj-3gSMF-7kA9JT-8VBQJX-6XfwDL-aaUhVY-6us67C-nqLMx7-95FwVE-dW52ER-ekqqxZ-f5EWZ7-bD3QnG-azHACF-2d1ebs-4pnRe7-a8x7N1-aKvFiX-c8SU6A-nAhRbL-bxzm7F-4wr7ZJ-hrX29-9U6cxS-5gknjQ-9u5Wvw-6YHDmi-kkyR4p-8jnvRE-7P2tfd-rFK9Nx-cvHKWA-bD3PH9-BPupf">[bastian.]/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p><em>The brain is key to our existence, but there’s a long way to go before neuroscience can truly capture its staggering capacity. For now, though, our <a href="https://theconversation.com/au/topics/brain-control-series-31489">Brain Control series</a> explores what we do know about the brain’s command of six central functions: language, mood, memory, vision, personality and motor skills – and what happens when things go wrong.</em></p>
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<p>When you read something, you first need to detect the words and then to interpret them by determining context and meaning. This complex process involves many brain regions. </p>
<p>Detecting text usually involves the <a href="http://neuroscience.uth.tmc.edu/s2/chapter15.html">optic nerve and other nerve bundles</a> delivering signals from the eyes to the visual cortex at the back of the brain. If you are reading in Braille, you use the <a href="http://neuroscience.uth.tmc.edu/s2/chapter04.html">sensory cortex</a> towards the top of the brain. If you listen to someone else reading, then you use the <a href="http://neuroscience.uth.tmc.edu/s2/chapter13.html">auditory cortex</a> not far from your ears. </p>
<p>A <a href="http://neuroscience.uth.tmc.edu/s4/chapter08.html">system of regions</a> towards the back and middle of your brain help you interpret the text. These include the <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4107834/">angular gyrus</a> in the parietal lobe, <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1749-6632.1976.tb25546.x/abstract">Wernicke’s area</a> (comprising mainly the top rear portion of the temporal lobe), <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4885738/">insular cortex</a>, <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2424405/">basal ganglia and cerebellum</a>.</p>
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<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/138932/original/image-20160923-25499-1v86vev.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/138932/original/image-20160923-25499-1v86vev.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=529&fit=crop&dpr=1 600w, https://images.theconversation.com/files/138932/original/image-20160923-25499-1v86vev.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=529&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/138932/original/image-20160923-25499-1v86vev.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=529&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/138932/original/image-20160923-25499-1v86vev.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=665&fit=crop&dpr=1 754w, https://images.theconversation.com/files/138932/original/image-20160923-25499-1v86vev.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=665&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/138932/original/image-20160923-25499-1v86vev.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=665&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="attribution"><span class="source">The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p>These regions work together as a network to process words and word sequences to determine context and meaning. This enables our receptive language abilities, which means the ability to understand language. Complementary to this is expressive language, which is the ability to produce language. </p>
<p>To speak sensibly, you must think of words to convey an idea or message, formulate them into a sentence according to grammatical rules and then use your lungs, vocal cords and mouth to create sounds. Regions in your frontal, temporal and parietal lobes formulate what you want to say and the <a href="http://neuroscience.uth.tmc.edu/s3/chapter03.html">motor cortex</a>, in your frontal lobe, enables you to speak the words.</p>
<p>Most of this language-related brain activity is likely occurring in the left side of your brain. But some people use an even mix of both sides and, rarely, some have right dominance for language. There is an evolutionary view that <a href="http://www.jneurosci.org/content/25/45/10351.long">specialisation of certain functions to one side or the other</a> may be an advantage, as many animals, especially vertebrates, exhibit brain function with prominence on one side.</p>
<p>Why the left side is favoured for language isn’t known. But we do know that injury or conditions such as <a href="http://www.neurology.org/content/67/10/1813">epilepsy, if it affects the left side of the brain</a> early in a child’s development, can increase the chances language will develop on the right side. The chance of the person being left-handed is also increased. This makes sense, because the left side of the body is controlled by the motor cortex on the right side of the brain.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/138756/original/image-20160922-22540-xt2j8i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/138756/original/image-20160922-22540-xt2j8i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=438&fit=crop&dpr=1 600w, https://images.theconversation.com/files/138756/original/image-20160922-22540-xt2j8i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=438&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/138756/original/image-20160922-22540-xt2j8i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=438&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/138756/original/image-20160922-22540-xt2j8i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=551&fit=crop&dpr=1 754w, https://images.theconversation.com/files/138756/original/image-20160922-22540-xt2j8i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=551&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/138756/original/image-20160922-22540-xt2j8i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=551&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">To speak sensibly, you must think of words to convey an idea or message, formulate them into a sentence according to grammatical rules and then use your lungs, vocal cords and mouth to create sounds.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/paulpod/478995331/in/photolist-JjYCc-yKtpE-6GWm9M-8Bo6Kj-eQM8tp-dB1fWn-53382S-5NyF79-abEHgE-qtbHu-8s9MD-iLV85-4vmaxd-4Q14um-eMgfdz-8kqWBn-aJifav-qvck3-8ku5Rw-o4rcHW-ac55u-7piWQa-dDNWKm-8kqUgt-ekqH7B-6Zo69a-86iZdJ-gCnhb3-m9KL4-5cDdfX-6DqwK3-6MBJJ-qpjzf-3cyUdJ-afF9dL-nr3wd-9t4HD2-6AQmA1-ojh79-2hshBG-3d7qaZ-agQ1vn-4VBLqh-4ebAFg-8pjxvJ-pkr9jn-cgc9fw-4rAjC4-Yfc67-aieCb3">paul pod/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Selective problems</h2>
<p>In 1861, French neurologist Pierre Paul Broca described a patient unable to speak who had no motor impairments to account for the inability. A postmortem examination showed a lesion in a large <a href="http://psychclassics.yorku.ca/Broca/perte-e.htm">area towards the lower middle of his left frontal lobe</a> particularly important in language formulation. This is now known as <a href="http://neuroscience.uth.tmc.edu/s4/chapter08.html">Broca’s area</a>. </p>
<p>The clinical symptom of being unable to speak despite having the motor skills is known as expressive aphasia, or Broca’s aphasia.</p>
<p>In 1867, Carl Wernicke observed an opposite phenomenon. A patient was able to speak but not understand language. This is known as receptive aphasia, or Wernicke’s aphasia. The damaged region, as you might correctly guess, is the Wernicke’s area mentioned above.</p>
<p>Scientists have also observed injured patients with <a href="http://link.springer.com/article/10.1007/BF01067101">other selective problems</a>, such as an inability to understand most words except nouns; or words with unusual spelling, such as those with silent consonants, like reign. </p>
<p>These difficulties are thought to arise from damage to selective areas or connections between regions in the brain’s language network. However, precise localisation can often be difficult given the complexity of individuals’ symptoms and the uncontrolled nature of their brain injury.</p>
<p>We also know the brain’s language regions work together as a <a href="http://www.sciencedirect.com/science/article/pii/S1053811912004703">co-ordinated network</a>, with some parts involved in multiple functions and a level of redundancy in some processing pathways. So it’s not simply a matter of one brain region doing one thing in isolation. </p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/138758/original/image-20160922-22530-1mflhwm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/138758/original/image-20160922-22530-1mflhwm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=778&fit=crop&dpr=1 600w, https://images.theconversation.com/files/138758/original/image-20160922-22530-1mflhwm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=778&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/138758/original/image-20160922-22530-1mflhwm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=778&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/138758/original/image-20160922-22530-1mflhwm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=977&fit=crop&dpr=1 754w, https://images.theconversation.com/files/138758/original/image-20160922-22530-1mflhwm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=977&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/138758/original/image-20160922-22530-1mflhwm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=977&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Broca’s area is named after French neurologist Pierre Paul Broca.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Paul_Broca_2.jpg">Wikimedia Commons</a></span>
</figcaption>
</figure>
<h2>How do we know all this?</h2>
<p>Before advanced medical imaging, most of our knowledge came from observing unfortunate patients with injuries to particular brain parts. One could relate the approximate region of damage to their specific symptoms. Broca’s and Wernicke’s observations are well-known examples.</p>
<p>Other knowledge was inferred from brain-stimulation studies. Weak electrical stimulation of the brain while a patient is awake is sometimes performed in patients undergoing surgery to remove a lesion such as a tumour. The stimulation causes that part of the brain to stop working for a few seconds, which can enable the surgeon to identify areas of critically important function to avoid damaging during surgery. </p>
<p>In the mid-20th century, this helped neurosurgeons discover more about the <a href="http://press.princeton.edu/titles/855.html">localisation of language function in the brain</a>. It was clearly demonstrated that while most people have language originating on the left side of their brain, some could have language originating on the right.</p>
<p>Towards the later part of the 20th century, if a surgeon needed to find out which side of your brain was responsible for language – so he didn’t do any damage – he would put to sleep one side of your brain with an anaesthetic. The doctor would then ask you a series of questions, determining your language side from your ability or inability to answer them. This invasive test (which is less often used today due to the availability of functional brain imaging) is <a href="http://www.tandfonline.com/doi/abs/10.1076/jhin.8.3.286.1819">known as the Wada test</a>, named after Juhn Wada, who first described it just after the second world war.</p>
<h2>Brain imaging</h2>
<p>Today, we can get a much better view of brain function by using imaging techniques, especially magnetic resonance imaging (MRI), a safe procedure that uses magnetic fields to take pictures of your brain. </p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/138760/original/image-20160922-22540-8fqobz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/138760/original/image-20160922-22540-8fqobz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/138760/original/image-20160922-22540-8fqobz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/138760/original/image-20160922-22540-8fqobz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/138760/original/image-20160922-22540-8fqobz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/138760/original/image-20160922-22540-8fqobz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/138760/original/image-20160922-22540-8fqobz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">When we see activity in a region of the brain, that’s when there is an increase in freshly oxygenated blood flow.</span>
<span class="attribution"><span class="source">from shutterstock.com</span></span>
</figcaption>
</figure>
<p>Using MRI to measure brain function is called functional MRI (fMRI), which detects signals from magnetic properties of blood in vessels supplying oxygen to brain cells. The fMRI signal changes depending on <a href="http://www.pnas.org/content/89/13/5951">whether the blood is carrying oxygen</a>, which means it slightly reduces the magnetic field, or has delivered up its oxygen, which slightly increases the magnetic field. </p>
<p>A few seconds after brain neurons become active in a brain region, there is an increase in freshly oxygenated blood flow to that brain part, much more than required to satisfy the oxygen demand of the neurons. This is what we see when we say a brain region is activated during certain functions.</p>
<p>Brain-imaging methods have revealed that much more of our brain is involved in language processing than previously thought. We now know that <a href="http://www.sciencedirect.com/science/article/pii/S1053811912004703">numerous regions in every major lobe</a> (frontal, parietal, occipital and temporal lobes; and the cerebellum, an area at the bottom of the brain) are involved in our ability to produce and comprehend language. </p>
<p>Functional MRI is also becoming a useful clinical tool. In some centres it has replaced the Wada test to <a href="http://www.ncbi.nlm.nih.gov/pubmed/20097290">determine where language is in the brain</a>. </p>
<p>Scientists are also using fMRI to build up a finer picture of how the brain processes language by designing experiments that compare which areas are active during various tasks. For instance, researchers have observed <a href="http://www.sciencedirect.com/science/article/pii/S0006322302013653">differences in brain language regions</a> of dyslexic children compared to those without dyslexia. </p>
<p>Researchers compared fMRI images of groups of children with and without dyslexia while they performed language-related tasks. They found that dyslexic children had, on average, less activity in Broca’s area mainly on the left during this task. They also had less activity in or near Wernicke’s area on the left and right, and a portion of the front of the temporal lobe on the right. </p>
<p>Could this type of brain imaging provide a diagnostic signature of dyslexia? This is a work-in-progress, but we hope further study will one day lead to a robust, objective and early brain-imaging test for dyslexia and other disorders.</p>
<hr>
<p><em>Want to know how the brain controls your mood? Read today’s accompanying piece <a href="http://theconversation.com/the-emotion-centre-is-the-oldest-part-of-the-human-brain-why-is-mood-so-important-63324">here</a>.</em></p><img src="https://counter.theconversation.com/content/63318/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Abbott receives fellowship funding from the Australian National Imaging Facility. He has received grants from the National Health and Medical Research Council (Australia), the Australian Research Council, and the National Institutes of Health (USA). David works at the Florey Institute of Neuroscience and Mental Health and has honorary affiliations with The University of Melbourne. The Florey acknowledges support from the Victorian Government and in particular the funding from the Operational Infrastructure Support Grant.</span></em></p>When you read this text, certain regions in your brain begin working more than others. Advanced imaging allows scientists to map the brain networks responsible for understanding language.David Abbott, Senior Research Fellow and Head of the Epilepsy Neuroinformatics Laboratory, Florey Institute of Neuroscience and Mental HealthLicensed as Creative Commons – attribution, no derivatives.