̽��ֱ�� of Cambridge - Centre for Speech Language and the Brain

Mechanisms of real-time speech interpretation in the human brain revealed

jg533 — Mon, 30 Sep 2019 19:00:00 +0000

In a study published today in the journal PNAS, researchers at the ̽��ֱ�� of Cambridge developed novel computational models of the meanings of words, and tested these directly against real-time brain activity in volunteers.

“Our ability to put words into context, depending on the other words around them, is an immediate process and it’s thanks to the best computer we’ve ever known: the brain in our head. It’s something we haven’t yet managed to fully replicate in computers because it is still so poorly understood,” said Lorraine Tyler, Director of the Centre for Speech, Language and the Brain at the ̽��ֱ�� of Cambridge, which ran the study.

Central to understanding speech are the processes involved in what is known as ‘semantic composition’ – in which the brain combines the meaning of words in a sentence as they are heard, so that they make sense in the context of what has already been said. This new study has revealed the detailed real-time processes going on inside the brain that make this possible.

By saying the phrase: “the elderly man ate the apple” and watching how the volunteers’ brains responded, the researchers could track the dynamic patterns of information flow between critical language regions in the brain.

As the word ‘eat’ is heard, it primes the brain to put constraints on how it interprets the next word in the sentence: ‘eat’ is likely to be something to do with food. ̽��ֱ��study shows how these constraints directly affect how the meaning of the next word in the sentence is understood, revealing the neural mechanisms underpinning this essential property of spoken language – our ability to combine sequences of words into meaningful expressions, millisecond by millisecond as the speech is heard.

“ ̽��ֱ��way our brain enables us to understand what someone is saying, as they’re saying it, is remarkable,” said Professor Tyler. “By looking at the real-time flow of information in the brain we’ve shown how word meanings are being rapidly interpreted and put into context.”

This research is funded by the European Research Council.

Reference
Lyu, B. et al; Neural dynamics of semantic composition. PNAS (2019). DOI: 10.1073/pnas.1903402116

Scientists have come a step closer to understanding how we’re able to understand spoken language so rapidly, and it involves a huge and complex set of computations in the brain.

̽��ֱ��way our brain enables us to understand what someone is saying, as they’re saying it, is remarkable. By looking at the real-time flow of information in the brain we’ve shown how word meanings are being rapidly interpreted and put into context.

Lorraine Tyler

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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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Your brain might not be as ‘old’ as you think

cjb250 — Mon, 09 Mar 2015 09:22:10 +0000

How ‘old’ is your brain? Put another way, how ‘aged’ is your brain? ̽��ֱ��standard, scientific answer, suggests that the older you get, the greater the changes in the activity of your neurons. In fact, my colleagues and I have found out that this isn’t necessarily the case: older brains may be more similar to younger brains than we’d previously thought.

In our study, published recently in the journal Human Brain Mapping, we’ve shown that changes in the ageing brain previously observed using functional magnetic resonance imaging (fMRI) – one of the standard ways of measuring brain activity – may be due to changes in our blood vessels, rather than changes in the activity of our nerve cells, our neurons. Given the large number of fMRI studies used to assess the ageing brain, this has important consequences for understanding how the brain changes with age and it challenges current theories of ageing.

̽��ֱ��fundamental problem of fMRI is that it measures the activity of our neurons indirectly through changes in regional blood flow. Without careful correction for age differences in how the blood vessels respond, differences in fMRI signals may be erroneously regarded as differences in our neurons.

An important line of research focuses on controlling for noise in fMRI signals using additional baseline measures of vascular (blood vessel) function, for example involving experimental manipulations of carbon dioxide levels in blood. However, such methods have not been widely used, possibly because they are impractical to implement in studies of ageing.

An alternative way of correcting makes use of the resting state, ’task-free’, fMRI measurement, which is easy to acquire and available in most fMRI experiments. While this method has been difficult to validate in the past, the unique combination of an impressively detailed data set across 335 healthy volunteers over the lifespan, as part of the Cambridge Centre for Ageing and Neuroscience (CamCAN) project, has allowed us to probe the true nature of the effects of ageing on resting state fMRI signal amplitude. This showed that age differences in signal amplitude at rest – in other words, while volunteers perform no task during the scan – originate from our blood vessels, not our nerve cells. We believe we can use this as a robust correction factor to control for vascular differences in fMRI studies of ageing.

A number of research studies have previously found reduced brain activity in the areas of the brain related to our senses and movement during tasks that study these aspects. Using conventional methods, we replicated these findings, but, after correction, we found that it is more likely to be vascular health, not brain function, that accounts for most age-related differences in fMRI signals in sensory areas. In other words, neuroscientists may have been overestimating age differences in brain activity in previous fMRI studies.

Why is this important? We’re an ageing society, with more and more people living into old age, so it’s crucial that we understand how age affects how the brain functions. We clearly need to refine our fMRI experiments, otherwise we risk creating a misleading picture of activity in the brain as we age. Without refinement, such fMRI studies may misinterpret the effect of age as a cognitive phenomenon, when really it has more to do with our blood vessels.

Dr Tsvetanov is funded by the Biotechnology and Biological Sciences Research Council (BBSRC).

Reference

Tsvetanov, KA et al. ̽��ֱ��effect of ageing on fMRI: correction for the confounding effects of vascular reactivity evaluated by joint fMRI and MEG in 335 adults. Human Brain Mapping; 27 February 2015

Our standard way of measuring brain activity could be giving us a misleading picture of how our brains age, argues Dr Kamen Tsvetanov from the Department of Psychology.

We’re an ageing society, with more and more people living into old age, so it’s crucial that we understand how age affects how the brain functions

Kamen Tsvetanov

Brain areas with rich blood supply lower their vascular reactivity with ageing

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