̽��ֱ�� of Cambridge - MRC Cognition and Brain Sciences Unit

Ageing affects test-taking, not language, study shows

cjb250 — Thu, 12 May 2016 10:18:05 +0000

Scientists from the Cambridge Centre for Ageing and Neuroscience (Cam-CAN) scanned participants during testing and found that the areas of the brain responsible for language performed just as well in older adults as in younger ones.

̽��ֱ��research, published in the Journal of Neuroscience, suggests that increased neural activation in the frontal brain regions of older adults reflects differences in the way they respond to the demands of the task compared with younger adults, rather than any difference in language processing itself.

“These findings suggest our ability to understand language is remarkably preserved well into old age, and it's not through some trick of the mind, or reorganisation of the brain,” says co-author Professor Lorraine Tyler, who leads Cam-CAN. “Instead, it's through the continued functioning of a well-used language processing machine common to all humans.”

Professor Tyler says cognitive neuroscientists attempting to explain how the mind and brain work typically approach the question with tasks designed to measure particular cognitive abilities, such as memory or language. However, it's rarely as simple as that, she says, and tasks never end up measuring only one thing.

“Scientists claim that they are studying language, when really they are studying language plus your motivation to do well, plus your understanding of the instructions, plus your ability to focus, and so on,” says lead author Dr Karen Campbell, now based at Harvard ̽��ֱ��. “These poorly defined tasks become even more problematic when it comes to studying the older brain, because older adults sometimes show increased neural activation in frontal brain regions, which is thought to reflect a change in how older brains carry out a given cognitive function. However, this extra activation may simply reflect differences in how young and older adults respond to the demands of the task.”

Campbell and her Cam-CAN colleagues tried to isolate the effect of the testing by scanning 111 participants aged 22-87 using functional magnetic resonance imaging (fMRI) while they either passively listened to sentences or decided if the sentences were grammatical or not.

̽��ֱ��researchers found that simply listening to and comprehending language, as we do in everyday life, “lights up” brain networks responsible for hearing and language, whereas performing a cognitive task with the same sentences leads to the additional activation of several task-related networks.

Age had no effect on the language network itself, but it did affect this network’s ability to “talk with” other task-related networks.

̽��ֱ��Cambridge Centre for Ageing and Neuroscience is funded by the Biotechnology and Biological Sciences Research Council and is jointly based at the ̽��ֱ�� of Cambridge and the Medical Research Council Cognition and Brain Sciences Unit.

Reference
Campbell, KL et al. Robust Resilience of the Frontotemporal Syntax System to Aging. Journal of Neuroscience; 11 May 2016; DOI: 10.1523/JNEUROSCI.4561-15.2016

̽��ֱ��ability to understand language could be much better preserved into old age than previously thought, according to researchers from the ̽��ֱ�� of Cambridge, who found older adults struggle more with test conditions than language processing.

Scientists claim that they are studying language, when really they are studying language plus your motivation to do well, plus your understanding of the instructions, plus your ability to focus, and so on

Karen Campbell

Pedro Ribeiro Simões

Talking

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Schizophrenia and the teenage brain: how can imaging help?

lw355 — Wed, 17 Feb 2016 11:02:18 +0000

Restless, disordered, uncertain, impulsive, emotional – the teenage brain can be a confused fury of neural firings and misfirings.

For most 14- to 24-year-olds – the “risky age” as Professor Ed Bullmore describes it – the maelstrom eventually subsides. For some, episodes of depression, low self-esteem, self-harm or paranoia may intensify and become more frequent. For around 1 in 100, the change in mental state is so marked that it will become difficult for them to distinguish their delusions and hallucinations from reality – one of the hallmarks of schizophrenia.

“Schizophrenia is a particularly feared diagnosis,” says Bullmore. “People tend to think it means a chronic lifelong dependency on medication and therapy. It can mean this, but it can also last only a few years. ̽��ֱ��main thing that patients and their families want to know is what does the future hold – am I likely to be able to resume my life, get a job, and so on?”

Bullmore is co-chair of Cambridge Neuroscience, an initiative to enhance multidisciplinary research across the ̽��ֱ��, and leads the Department of Psychiatry, where he and colleagues have been developing imaging techniques that are revealing where and over what timescale abnormalities in the brain develop in people with mental health problems.

This is no easy task. Even being able to show a neural abnormality has been a major and relatively recent advance for understanding a condition that, Bullmore says, has in the past been regarded with prejudice and assumptions. “Demonstrating neural change moves us away from what might be regarded as a blaming approach where someone is made to feel personally responsible for the fact these symptoms exist. Imaging shows you that’s not the case – there is a biological basis.”

̽��ֱ��task is made difficult because there is no single event or area of the brain that underlies schizophrenia. It has only been from the collation of results from imaging studies worldwide that it has become apparent that when it comes to mental health disorders the scientists need to look at the big picture – the changes happening in wiring circuits across the whole brain.

Imaging techniques such as magnetic resonance imaging (MRI) are helping to map the brain in unprecedented detail. Structural MRI follows the movement of water as it diffuses along the pathways forged by neurons – showing the network of connections spread across the brain. Functional MRI measures slow rhythmic activity in the brain; if two areas of the brain show activity at the same time the chances are they are functionally connected. Bullmore and colleagues have developed mathematical methods to calculate the probability of there being such a connection.

“Neuroscience is no longer just about neurons,” he explains. “We can also now talk in terms of hubs, networks and connectomes. If the brain is thought of as a computer, with ‘processors’ in the outer grey matter and ‘wires’ that connect them in the inner white matter, some hub regions are more highly connected than others.”

In schizophrenia, connectivity in the wiring diagram goes awry and highly connected hubs are especially affected – “you could call it a hubopathy,” says Bullmore. His team’s research has demonstrated that those who have suffered decades of schizophrenia have large-scale network abnormalities compared with a healthy brain, which goes some way to explaining the diversity and severity of symptoms experienced in schizophrenia. ̽��ֱ��question is: can imaging be used to chart this progression?

Bullmore and his colleagues believe so: “Roughly a third of patients recover, a third have intermittent symptoms and a third will be affected for decades by schizophrenia. At diagnosis we can’t currently tell which of these outcomes lies in store. But we think one day we will be able to correlate the pattern of network activity with future outcome.”

It’s not only what happens to patients post-diagnosis that interests Bullmore, but also what has happened neurologically in the years before diagnosis.

“For me, one of the most exciting aspects of psychiatry is that we can use imaging to study the ‘risky age’ of brain development to understand how the connectome grows or matures in healthy brains. We can then start to pinpoint which genetic and environmental factors might favour healthy adolescent brain network development and which factors might predispose to abnormal network development, leading to chronic disability or distress.”

In 2012, Bullmore and colleagues Professor Ian Goodyer and Professor Peter Jones in Cambridge’s Department of Psychiatry (in collaboration with Professor Ray Dolan and Professor Peter Fonagy from ̽��ֱ�� College London) launched the NeuroScience in Psychiatry Network, funded by the Wellcome Trust. They have been recruiting a panel of 2,000 healthy volunteers aged 14–24 years, 300 of whom have had brain scans to contribute to one of the most comprehensive ‘circuit diagrams’ of the teenage brain ever attempted.

“Remarkably little is known about how brain networks grow during the crucial transition from childhood dependence to life as independent adults,” adds Bullmore. “ ̽��ֱ��adolescent brain is still a bit of a black box. But it is a big step forward that we can now see healthy human brain development much more clearly, especially with the next-generation brain scanners coming to Cambridge soon [see panel]. It’s very exciting to think that we should then be able to understand and predict the pathways of brain network development that lead to schizophrenia.”

Adolescence is a dangerous time for the onset of mental health problems. Advances in brain imaging are helping to picture how neural changes in these crucial years can lead to chronic debilitating mental illness.

Neuroscience is no longer just about neurons. We can also now talk in terms of hubs, networks and connectomes.

Ed Bullmore

̽��ֱ��District

Scientists are looking at the 'bigger picture' of mental health

Opening the black box

̽��ֱ��arrival of two state-of-the-art MRI machines in Cambridge, thanks to funding from the Medical Research Council (MRC), will revolutionise the study of the brain.

“A brain scan is much more than an image,” contends Ed Bullmore. “It’s really a very large collection of numbers. With the best scanners and some high-performance computing, you can start to think not only about disease mechanisms but also about identifying early risk factors and preventative action.”

Two of the newest scanners in the UK will arrive at the Cambridge Biomedical Campus in 2016, and a new high-speed secure link will be created through to the recently opened £20 million West Cambridge Data Centre, which will analyse the data.

One scanner, a new 7-Tesla ‘ultrahigh-field’ MRI machine, will help researchers see how the human brain works as a whole, yet also with the precision of a grain of sand a fraction of a millimetre across. It will further the study of dementia, brain injury, obesity, addiction, mental health disorders, pain and stroke.

‘7T’ is a collaboration between the ̽��ֱ�� and the MRC’s Cognition and Brain Sciences Unit (CBSU). Professor James Rowe, from the Department of Clinical Neurosciences and the CBSU, explains: “ ̽��ֱ��new scanner is a major advance to study the details of the human brain not only in health but also the effects of age and the origins of brain diseases. ̽��ֱ��unprecedented detail and sensitivity at 7T is essential in the national effort towards a cure for dementia and mental illness.”

Joining the 7T scanner will be a positron emission tomography (PET)–MRI machine, which shows changes in the brain down to the level of individual molecules. Until now only two PET–MRI scanners existed in the UK, but MRC Dementias Platform UK has invested in five more nationally, creating what is thought to be the first nationally coordinated MRI–PET network anywhere in the world.

“Beating dementia is a long-term goal,” adds Rowe. “These scanners will make a very significant contribution to this eventual success and to the lives of patients and their families.”

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

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Listen to your heart: why your brain may give away how well you know yourself

sc604 — Mon, 20 Apr 2015 23:01:17 +0000

In research published today in the journal Cerebral Cortex, a team of scientists led by the ̽��ֱ�� of Cambridge and the Medical Research Council (MRC) Cognition and Brain Sciences Unit, Cambridge, studied not only whether volunteers could be trained to follow their heartbeat, but whether it was possible to identify from brain activity how good they were at estimating their performance.

Dr Tristan Bekinschtein, a Wellcome Trust Fellow and lecturer in the Department of Psychology at the ̽��ֱ�� of Cambridge, says: “‘Follow your heart’ has become something of a cliché, but we know that, consciously or unconsciously, there is a relationship between our heart rate and our decisions and emotions. There may well be benefits to becoming more attuned to our heartbeat, but there’s very little in scientific literature about whether this is even technically possible.”

A recent study from Dr Bekinschtein and colleagues showed that people with ‘depersonalisation-derealisation disorder’ – in which patients repeatedly feel that they are observing themselves from outside their body or have a sense that things around them are not real – perform particularly badly at listening to their heart. Another study from the team, looking at a man with two hearts – his natural, diseased heart and a replacement artificial heart – found that he was better able to tune into the artificial heart than the diseased one.

Other studies have highlighted a possible connection between heart rate and task performance. For example, in one study, volunteers given the drug propranolol to increase their heart rate performed worse at emotional tasks than the control group. Changing heart rate is part of our automatic and unconscious ‘fight or flight’ response – being aware of the heart’s rhythm could give people more control over their behaviour, believe the researchers.

Thirty-three volunteers took part in an experiment during which scientists measured their brain activity using an electroencephalograph (EEG). First off, the volunteers were asked to tap in synchrony as they listened to a regular and then irregular heartbeat. Next, they were asked to tap out their own heartbeat in synchrony. Then, they were asked to tap out their own heartbeat whilst listening to it through a stethoscope. Finally, the stethoscopes were removed and they were once again asked to tap out their heartbeat.

During the task, when the volunteers were tapping out their heartbeat unaided, they were asked to rate their performance on a scale of 1 to 10, with 1 being ‘inaccurate’ and 10 ‘extremely accurate’. Once the task was completed, they were asked how much they thought they had improved from 1 (‘did not improve’) to 10 (‘improved a lot’).

“Perhaps unsurprisingly, we found that brain activity differed between people who improved at tapping out their heartbeat and those who did not,” says Andrés Canales-Johnson from the MRC Cognition and Brain Sciences Unit. “But interestingly, brain activity also differed between people who knew whether or not they had improved and those people who under- or over-estimated their own performance.”

Just over four in ten (42%) of the participants showed significant improvement in their ability to accurately tap along unaided with their heartbeat. This is most likely due to the fact that listening to their heartbeat through a stethoscope had allowed them to fine tune their attention to the otherwise faint signal of their heartbeat. In those whose performance had improved, the researchers saw a stronger brain signal known as the ‘heartbeat evoked potential’ (HEP) across the brain.

̽��ֱ��researchers found no significant differences in the HEP when grouping the participants by how well they thought they had performed – their subjective performance. This suggests that the HEP provides a marker of objective performance.

In the final part of the test – after the participants had listened to their heartbeat through the stethoscope and were once again tapping unaided – the researchers found differences in brain activity between participants. Crucially, they found an increase in ‘gamma phase synchrony’ – coordinated ‘chatter’ between different regions in the brain – in only those learners whose subjective judgement of their own performance matched their actual, objective performance. In other words, this activity was seen only in learners who knew they had performed badly or knew they had improved.

“We’ve shown that for just under half of us, training can help us listen to our hearts, but we may not be aware of our progress,” adds Dr Bekinschtein. “Some people find this task easier to do than others do. Also, some people clearly don’t know how good or bad they actually are – but their brain activity gives them away.

“There are techniques such as mindfulness that teach us to be more aware of our bodies, but it will be interesting to see whether people are able to control their emotions better or to make better decisions if they are aware of how their heart is beating.”

̽��ֱ��research was supported by the Wellcome Trust and the MRC in the UK, and the Chilean National Fund for Scientific and Technological Development, the Argentinean National Research Council for Science and Technology, and the Argentinean Agency for National Scientific Promotion.

“Listen to your heart,” sang Swedish pop group Roxette in the late Eighties. But not everyone is able to tune into their heartbeat, according to an international team of researchers – and half of us under- or over-estimate our ability.

'Follow your heart’ has become something of a cliché, but we know that, consciously or unconsciously, there is a relationship between our heartrate and our decisions and emotions

Tristan Bekinschtein

Larissa S.

listen to your heart

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Recalling memories may make us forget

cjb250 — Mon, 16 Mar 2015 16:00:00 +0000

̽��ֱ��research, published today in Nature Neuroscience, is the first to isolate the adaptive forgetting mechanism in the human brain. ̽��ֱ��brain imaging study shows that the mechanism itself is implemented by the suppression of unique patterns in the cortex that underlie competing memories. Via this mechanism, remembering dynamically alters which aspects of our past remain accessible.

In a study funded by the Medical Research Council (MRC), researchers monitored patterns of brain activity in the participants using magnetic resonance imaging (MRI) scans while the participants were asked to recall individual memories based on images they had been shown earlier.

̽��ֱ��team from the ̽��ֱ�� of Cambridge, the MRC Cognition and Brain Sciences Unit, Cambridge, and the ̽��ֱ�� of Birmingham, was able to track the brain activity induced by individual memories and show how this suppressed others by dividing the brain into tiny voxels (3D pixels). Based on the fine-grained activation patterns of these voxels, the researchers were able to witness the neural fate of individual memories as they were initially reactivated, and subsequently suppressed.

Over the course of four selective retrievals the participants in the study were cued to retrieve a target memory, which became more vivid with each trial. Competing memories were less well reactivated as each trial was carried out, and indeed were pushed below baseline expectations for memory, supporting the idea that an active suppression of memory was taking place.

Dr Michael Anderson from the MRC Cognition and Brain Sciences Unit and the Behavioural and Clinical Neurosciences Institute at the ̽��ֱ�� of Cambridge said: “People are used to thinking of forgetting as something passive. Our research reveals that people are more engaged than they realise in shaping what they remember of their lives. ̽��ֱ��idea that the very act of remembering can cause forgetting is surprising, and could tell us more about selective memory and even self-deception.”

Dr Maria Wimber from the ̽��ֱ�� of Birmingham added: “Forgetting is often viewed as a negative thing, but of course, it can be incredibly useful when trying to overcome a negative memory from our past. So there are opportunities for this to be applied in areas to really help people.”

̽��ֱ��team note that their findings may have implications for the judicial process, for example, in eyewitness testimonies. When a witness is asked to recall specific information about an event and is quizzed time and time again, it could well be to the detriment of associated memories, giving the impression that their memory is sketchy.

Studying the neural basis of forgetting has proven challenging in the past because the ’engram’ – the unique neural fingerprint that an experience leaves in our memory – has been difficult to pinpoint in brain activity. By capitalising on the relationship between perception and memory, the study detected neural activity caused by the activation of individual memories, giving a unique window into the invisible neurocognitive processes triggered when a reminder recapitulates several competing memories.

Adapted from a press release by the Medical Research Council.

Reference
Wimber, M et al. Retrieval induces adaptive forgetting of competing memories via cortical pattern suppression. Nature Neuroscience; 16 March 2015

Intentionally recalling memories may lead us to forget other competing experiences that interfere with retrieval, according to a study published today. In other words, the very act of remembering may be one of the major reasons why we forget.

̽��ֱ��idea that the very act of remembering can cause forgetting is surprising, and could tell us more about selective memory and even self-deception

Michael Anderson

Sara

Forgetting

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Scientists find ‘hidden brain signatures’ of consciousness in vegetative state patients

cjb250 — Thu, 16 Oct 2014 18:00:24 +0000

There has been a great deal of interest recently in how much patients in a vegetative state following severe brain injury are aware of their surroundings. Although unable to move and respond, some of these patients are able to carry out tasks such as imagining playing a game of tennis. Using a functional magnetic resonance imaging (fMRI) scanner, which measures brain activity, researchers have previously been able to record activity in the pre-motor cortex, the part of the brain which deals with movement, in apparently unconscious patients asked to imagine playing tennis.

Now, a team of researchers led by scientists at the ̽��ֱ�� of Cambridge and the MRC Cognition and Brain Sciences Unit, Cambridge, have used high-density electroencephalographs (EEG) and a branch of mathematics known as ‘graph theory’ to study networks of activity in the brains of 32 patients diagnosed as vegetative and minimally conscious and compare them to healthy adults. ̽��ֱ��findings of the research are published today in the journal PLOS Computational Biology. ̽��ֱ��study was funded mainly by the Wellcome Trust, the National Institute of Health Research Cambridge Biomedical Research Centre and the Medical Research Council (MRC).

̽��ֱ��researchers showed that the rich and diversely connected networks that support awareness in the healthy brain are typically – but importantly, not always – impaired in patients in a vegetative state. Some vegetative patients had well-preserved brain networks that look similar to those of healthy adults – these patients were those who had shown signs of hidden awareness by following commands such as imagining playing tennis.

Dr Srivas Chennu from the Department of Clinical Neurosciences at the ̽��ֱ�� of Cambridge says: “Understanding how consciousness arises from the interactions between networks of brain regions is an elusive but fascinating scientific question. But for patients diagnosed as vegetative and minimally conscious, and their families, this is far more than just an academic question – it takes on a very real significance. Our research could improve clinical assessment and help identify patients who might be covertly aware despite being uncommunicative.”

̽��ֱ��findings could help researchers develop a relatively simple way of identifying which patients might be aware whilst in a vegetative state. Unlike the ‘tennis test’, which can be a difficult task for patients and requires expensive and often unavailable fMRI scanners, this new technique uses EEG and could therefore be administered at a patient’s bedside. However, the tennis test is stronger evidence that the patient is indeed conscious, to the extent that they can follow commands using their thoughts. ̽��ֱ��researchers believe that a combination of such tests could help improve accuracy in the prognosis for a patient.

Dr Tristan Bekinschtein from the MRC Cognition and Brain Sciences Unit and the Department of Psychology, ̽��ֱ�� of Cambridge, adds: “Although there are limitations to how predictive our test would be used in isolation, combined with other tests it could help in the clinical assessment of patients. If a patient’s ‘awareness’ networks are intact, then we know that they are likely to be aware of what is going on around them. But unfortunately, they also suggest that vegetative patients with severely impaired networks at rest are unlikely to show any signs of consciousness.”

Listen to Srivas Chennu interviewed on the BBC Radio 4 Today Programme below:

listen to ‘How to determine brain activity in someone in a persistent vegetative state’ on audioBoom

Reference
Chennu S et al. Spectral Signatures of Reorganised Brain Networks in Disorders of Consciousness. PLOS Computational Biology; 16 Oct 2014

Scientists in Cambridge have found hidden signatures in the brains of people in a vegetative state, which point to networks that could support consciousness even when a patient appears to be unconscious and unresponsive. ̽��ֱ��study could help doctors identify patients who are aware despite being unable to communicate.

Understanding how consciousness arises [in the brain] is an elusive but fascinating scientific question. But for patients diagnosed as vegetative and minimally conscious, and their families, this is far more than just an academic question – it takes on a very real significance

Srivas Chennu

Brain networks in two behaviourally-similar vegetative patients (left and middle), but one of whom imagined playing tennis (middle panel), alongside a healthy adult (right panel)

Yes

̽��ֱ��communicative brain

lw355 — Tue, 29 Nov 2011 10:00:57 +0000

̽��ֱ��ability to communicate using language is fundamental to the distinctive and remarkable success of the modern human. It is this capacity that separates us most decisively from our primate cousins, despite all that we have in common across species as intelligent social primates.

A major challenge for the cognitive neurosciences is to understand this relationship: what is the neurobiological context in which human language and communication have emerged, and what are the special human properties that make language itself possible?

For the past 150 years, scientific thinking about this relationship has been dominated by the concept of a single, central language system built around the brain’s left hemisphere. Pioneering 19th-century neurologists Paul Broca and Carl Wernicke noticed that patients with left hemisphere brain damage had difficulties with language comprehension and language production. Two areas of the left frontal and temporal lobes, Broca’s area and Wernicke’s area, and the bundle of nerve fibres connecting them, were identified as critical for speaking and understanding language.

Recent research in our laboratories suggests major limitations to this classic approach to language and the brain. ̽��ֱ��Broca–Wernicke concept captures one important aspect of the neural language system – the key role of the left hemisphere network – but it obscures another, equally important one. This is the role of bi-hemispheric systems and processes, whereby both left and right hemispheres work together to provide the fundamental underpinnings for human communicative processes.

A more fruitful approach to human language and communication will require a dual neurobiological framework in which these capacities are supported by two intersecting but evolutionarily and functionally distinguishable subsystems. ̽��ֱ��historical failure to make this separation has, we suggest, severely undermined scientific attempts to understand language, both as a neurocognitive phenomenon in the modern human, and in terms of its evolutionary and neurobiological context.

Dual systems

A strong evolutionary continuity between humans and our primate relatives is provided by a distributed, bi-hemispheric set of capacities that support the dynamic interpretation of visual and auditory signals in the service of social communication. These capacities have been the object of intensive study in monkeys and apes, and there is good evidence that their basic architecture underpins related communicative functions in the human.

In the context of human language comprehension, the bi-hemispheric systems support the ability not only to identify the words a speaker is producing – typically by integrating auditory and visual cues in face-to-face interaction – but also to make sense of these word-meanings in the general context of the listener’s knowledge of the world and of the specific context of speaking.

Where we see divergence between humans and other primates is in the domain of grammatical (or syntactic) function. Primate communication systems are not remotely comparable to human language in their expressive capacities. Human language is much more than a set of signs that stand for things. It constitutes a powerful and flexible set of grammatical devices for organising the flow of linguistic information and its interpretation, allowing us to represent and combine abstract linguistic elements, where these elements convey not only meaning but also the subtle structural cues that indicate how these elements are linked together.

It is the fronto-temporal network of regions in the left hemisphere that mediates these core grammatical functions in humans. This is a network that differs neuroanatomically from those of the brains of other primates, showing substantial increases in size, complexity and connectivity.

Although it’s not yet understood just how these evolutionary changes in the left hemisphere provide the neural substrate on which grammatical functions depend, it is clear that they are essential. When the left hemisphere system is damaged, the parallel right hemisphere regions cannot take over these functions, even when damage is sustained early in childhood.

Critically, however, the left hemisphere system that has emerged in humans neither replaces nor displaces the bi-hemispheric system for social communication and action found in both humans and other primates. It interacts and combines with it to create a co-ordinated process of linguistically guided communication and social interaction.

Functional separability

̽��ֱ��most direct evidence for a dual system approach is the ability to separate these systems in the modern human. Using a combination of behavioural and neuroimaging techniques, we have been able to demonstrate this both in patients with left hemisphere brain damage and in unimpaired young adults.

In the research with patients (conducted with Dr Paul Wright in the Department of Experimental Psychology and Dr Emmanuel Stamatakis in the Division of Anaesthesia) we focus on the comprehension of spoken words and spoken sentences. In initial testing, patients perform classic measures of syntactic function, where they match different spoken sentences to sets of pictures. Shown three pictures – a woman pushing a girl, a girl pushing a woman and a woman teaching a girl – patients will correctly match the sentence ‘ ̽��ֱ��woman pushed the girl’ to the first picture but will incorrectly match the passive sentence ‘ ̽��ֱ��woman is being pushed by the girl’ to the same picture. ̽��ֱ��second sentence requires the use of syntactic cues to extract the right meaning – just using the order of words is not sufficient.

These behavioural tests of syntactic impairment are linked, in the same patients, to their performance in the neuroimaging laboratory, where they hear sentences that vary in their syntactic demands, and where the precise extent of the injury to their brains can be mapped out. When we put these different sources of information together, we see that damage to the left hemisphere system progressively impairs the syntactic aspects of language processing – the more damage, the worse the performance.

Critically, however, the amount of left hemisphere damage, and the extent to which it involves the key fronto-temporal circuit, does not affect the patients’ ability to identify the words being spoken or to understand the messages being communicated – so long as syntactic cues are not required to do so. These capacities are supported bi-hemispherically, and can remain relatively intact even in the face of massive left hemisphere damage.

In work carried out with Dr Mirjana Bozic, then based at the Medical Research Council (MRC) Cognition and Brain Sciences Unit in Cambridge, we have been able to delineate these systems in the undamaged brain, using functional neuroimaging to tease out the different processing regions that are engaged by speech inputs with different properties.

Listeners hear either words that are specifically linguistically complex (words like played, which have the grammatical inflection ‘ed’), or words that make more general demands on the language processing system (words like ramp, which have another word, ram, embedded in them). Using an analysis technique that identifies the separate dimensions of the brain’s response to these sets of words, we see that the linguistically complex words activate a response component that is restricted to the left fronto-temporal region. By contrast, words that are perceptually complex, due to increased competition between the whole word and the embedded word, activate a strongly bi-hemispheric set of regions, partially overlapping with the linguistic component. Even in the intact brain, therefore, we can see the dynamic allocation of processing resources across the two systems, as a function of their joint roles in the communicative process.

Implications

A dual systems account of the ‘communicative brain’ is likely to have important and illuminating consequences for the sciences of language and its disorders.

In the context of left hemisphere brain damage we can better appreciate – and build upon for rehabilitation – the substantial bi-hemispheric communicative capacities the patient may still possess. In first- and second-language acquisition, we can better understand the learning trajectories that lead to language proficiency in terms of the relative contributions of these two aspects of communicative function.

̽��ֱ��approach also provides a new perspective on the variation between languages, where different languages may load more or less heavily on the different computational resources made available by the two systems. Most importantly, it enables us to clarify and focus the core issues for a neurobiological account of language and communication, a scientific domain clouded by ideology and inconsistency.

What is it about the human brain that makes language possible? Two evolutionary systems working together, say neuroscientists Professor William Marslen-Wilson and Professor Lorraine Tyler.

William Marslen-Wilson and Lorraine Tyler

Functional neuroimaging of the human brain

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Serotonin levels affect the brain’s response to anger

gm349 — Thu, 15 Sep 2011 08:30:36 +0000

Fluctuations of serotonin levels in the brain, which often occur when someone hasn’t eaten or is stressed, affects brain regions that enable people to regulate anger, new research from the ̽��ֱ�� of Cambridge has shown.

Although reduced serotonin levels have previously been implicated in aggression, this is the first study which has shown how this chemical helps regulate behaviour in the brain as well as why some individuals may be more prone to aggression. ̽��ֱ��research findings were published today, 15 September, in the journal Biological Psychiatry.

For the study, healthy volunteers’ serotonin levels were altered by manipulating their diet. On the serotonin depletion day, they were given a mixture of amino acids that lacked tryptophan, the building block for serotonin. On the placebo day, they were given the same mixture but with a normal amount of tryptophan.

̽��ֱ��researchers then scanned the volunteers’ brains using functional magnetic resonance imaging (fMRI) as they viewed faces with angry, sad, and neutral expressions. Using the fMRI, they were able to measure how different brain regions reacted and communicated with one another when the volunteers viewed angry faces, as opposed to sad or neutral faces.

̽��ֱ��research revealed that low brain serotonin made communications between specific brain regions of the emotional limbic system of the brain (a structure called the amygdala) and the frontal lobes weaker compared to those present under normal levels of serotonin. ̽��ֱ��findings suggest that when serotonin levels are low, it may be more difficult for the prefrontal cortex to control emotional responses to anger that are generated within the amygdala.

Using a personality questionnaire, they also determined which individuals have a natural tendency to behave aggressively. In these individuals, the communications between the amygdala and the prefrontal cortex was even weaker following serotonin depletion. 'Weak' communications means that it is more difficult for the prefrontal cortex to control the feelings of anger that are generated within the amygdala when the levels of serotonin are low. As a result, those individuals who might be predisposed to aggression were the most sensitive to changes in serotonin depletion.

Dr Molly Crockett, co-first author who worked on the research while a PhD student at Cambridge’s Behavioural and Clinical Neuroscience Institute (and currently based at the ̽��ֱ�� of Zurich) said: “We've known for decades that serotonin plays a key role in aggression, but it's only very recently that we've had the technology to look into the brain and examine just how serotonin helps us regulate our emotional impulses. By combining a long tradition in behavioral research with new technology, we were finally able to uncover a mechanism for how serotonin might influence aggression.”

Dr Luca Passamonti, co-first author who worked on the research while a visiting scientist at the Medical Research Council Cognition and Brain Sciences Unit in Cambridge (and currently based at the Consiglio Nazionale delle Ricerche (CNR), Unità di Ricerca Neuroimmagini, Catanzaro), said: “Although these results came from healthy volunteers, they are also relevant for a broad range of psychiatric disorders in which violence is a common problem. For example, these results may help to explain the brain mechanisms of a psychiatric disorder known as intermittent explosive disorder (IED). Individuals with IED typically show intense, extreme and uncontrollable outbursts of violence which may be triggered by cues of provocation such as a facial expression of anger.

“We are hopeful that our research will lead to improved diagnostics as well as better treatments for this and other conditions.”

Research provides new insight into why some individuals may be more aggressive than others.

By combining a long tradition in behavioral research with new technology, we were finally able to uncover a mechanism for how serotonin might influence aggression.

Dr Molly Crockett, co-first author who worked on the research while a PhD student at the ̽��ֱ�� of Cambridge’s Behavioural and Clinical Neuroscience Institute (and currently based at the ̽��ֱ�� of Zurich)

Mark Lythgoe and Chloe-Hutton from Wellcome Images

Digitally enhanced MRI of the human head showing the brain and spinal cord in blue/green and the other tissues in red and pink.

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