̽��ֱ�� of Cambridge - Cambridge Centre for Ageing and Neuroscience

Brains of overweight people ‘ten years older’ than lean counterparts at middle-age

cjb250 — Thu, 04 Aug 2016 09:10:08 +0000

Our brains naturally shrink with age, but scientists are increasingly recognising that obesity – already linked to conditions such as diabetes, cancer and heart disease – may also affect the onset and progression of brain ageing; however, direct studies to support this link are lacking.

In a cross-sectional study – in other words, a study that looks at data from individuals at one point in time – researchers looked at the impact of obesity on brain structure across the adult lifespan to investigate whether obesity was associated with brain changes characteristic of ageing. ̽��ֱ��team studied data from 473 individuals between the ages of 20 and 87, recruited by the Cambridge Centre for Aging and Neuroscience. ̽��ֱ��results are published in the journal Neurobiology of Aging.

̽��ֱ��researchers divided the data into two categories based on weight: lean and overweight. They found striking differences in the volume of white matter in the brains of overweight individuals compared with those of their leaner counterparts. Overweight individuals had a widespread reduction in white matter compared to lean people.

Comparison of grey matter (brown) and white matter (yellow) in sex-matched subjects A (56 years, BMI 19.5) and B (50 years, BMI 43.4). Credit: Lisa Ronan

̽��ֱ��team then calculated how white matter volume related to age across the two groups. They discovered that an overweight person at, say, 50 years old had a comparable white matter volume to a lean person aged 60 years, implying a difference in brain age of 10 years.

Strikingly, however, the researchers only observed these differences from middle-age onwards, suggesting that our brains may be particularly vulnerable during this period of ageing.

“As our brains age, they naturally shrink in size, but it isn’t clear why people who are overweight have a greater reduction in the amount of white matter,” says first author Dr Lisa Ronan from the Department of Psychiatry at the ̽��ֱ�� of Cambridge, “We can only speculate on whether obesity might in some way cause these changes or whether obesity is a consequence of brain changes.”

Senior author Professor Paul Fletcher, from the Department of Psychiatry, adds: “We’re living in an ageing population, with increasing levels of obesity, so it’s essential that we establish how these two factors might interact, since the consequences for health are potentially serious.

“ ̽��ֱ��fact that we only saw these differences from middle-age onwards raises the possibility that we may be particularly vulnerable at this age. It will also be important to find out whether these changes could be reversible with weight loss, which may well be the case.”

Despite the clear differences in the volume of white matter between lean and overweight individuals, the researchers found no connection between being overweight or obese and an individual’s cognitive abilities, as measured using a standard test similar to an IQ test.

Co-author Professor Sadaf Farooqi, from the Wellcome Trust–Medical Research Council Institute of Metabolic Science at Cambridge, says: “We don’t yet know the implications of these changes in brain structure. Clearly, this must be a starting point for us to explore in more depth the effects of weight, diet and exercise on the brain and memory.”

̽��ֱ��research was supported by the Bernard Wolfe Health Neuroscience Fund, the Wellcome Trust and the Biotechnology and Biological Sciences Research Council.

Reference
Ronan, L et al. Obesity associated with increased brain-age from mid-life. Neurobiology of Aging; e-pub 27 July 2016; DOI: 10.1016/j.neurobiolaging.2016.07.010

From middle-age, the brains of obese individuals display differences in white matter similar to those in lean individuals ten years their senior, according to new research led by the ̽��ֱ�� of Cambridge. White matter is the tissue that connects areas of the brain and allows for information to be communicated between regions.

We’re living in an ageing population, with increasing levels of obesity, so it’s essential that we establish how these two factors might interact, since the consequences for health are potentially serious

Paul Fletcher

Ben Watkin

Measuring tape

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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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Young minds think alike – and older people are more distractible

cjb250 — Fri, 14 Aug 2015 08:45:01 +0000

̽��ֱ��study, published today in the journal Neurobiology of Aging, also found that older people tended to be more easily distracted than younger adults.

Age is believed to change the way our brains respond and how its networks interact, but studies looking at these changes tend to use very artificial experiments, with basic stimuli. To try to understand how we respond to complex, life-like stimuli, researchers at the Cambridge Centre for Ageing and Neuroscience (Cam-CAN) showed 218 subjects aged 18-88 an edited version of an episode from the Hitchcock TV series while using functional magnetic resonance imaging (fMRI) to measure their brain activity.

̽��ֱ��researchers found a surprising degree of similarity in the thought patterns amongst the younger subjects – their brains tended to ‘light up’ in similar ways and at similar points in the programme. However, in older subjects, this similarity tended to disappear and their thought processes became more idiosyncratic, suggesting that they were responding differently to what they were watching and were possibly more distracted.

̽��ֱ��greatest differences were seen in the ‘higher order’ regions at the front of the brain, which are responsible for controlling attention (the superior frontal lobe and the intraparietal sulcus) and language processing (the bilateral middle temporal gyrus and left inferior frontal gyrus).

̽��ֱ��findings suggest that our ability to respond to everyday events in the environment differs with age, possibly due to altered patterns of attention.

Dr Karen Campbell from the Department of Psychology, first author on the study, says: “As we age, our ability to control the focus of attention tends to decline, and we end up attending to more ‘distracting’ information than younger adults. As a result, older adults end up attending to a more diverse range of stimuli and so are more likely to understand and interpret everyday events in different ways than younger people.”

In order to encourage audiences to respond to movies and TV programmes in the same way as everyone else, and hence have a ‘shared experience’, directors and cinematographers use a variety of techniques to draw attention to the focal item in each shot. When the stimulus is less engaging – for example, when one character is talking at length or the action is slow, people show less overlap in their neural patterns of activity, suggesting that a stimulus needs to be sufficiently captivating in order to drive attention. However, capturing attention is not sufficient when watching a film; the brain needs to maintain attention or at the very least, to limit attention to that information which is most relevant to the plot.

Dr Campbell and colleagues argue that the variety in brain patterns seen amongst older people reflects a difference in their ability to control their attention, as attentional capture by stimuli in the environment is known to be relatively preserved with age. This supports previous research which shows that older adults respond to and better remember materials with emotional content.

“We know that regions at the front of the brain are responsible for maintaining our attention, and these are the areas that see the greatest structural changes as we ages, and it is these changes that we believe are being reflected in our study,” she adds. “There may well be benefits to this distractibility. Attending to lots of different information could help with our creativity, for example.”

Cam-CAN is supported by the Biotechnology and Biological Sciences Research Council (BBSRC).

Reference
Campbell, K et al. Idiosyncratic responding during movie-watching predicted by age differences in attentional control. Neurobiology of Aging; 6 Aug 2015.

‘Bang! You’re Dead’, a 1961 episode of Alfred Hitchcock Presents, continues to surprise – but not just with the twist in its tale. Scientists at the ̽��ֱ�� of Cambridge have used the programme to show that young people respond in a similar way to events, but as we age our thought patterns diverge.

Older adults end up attending to a more diverse range of stimuli and so are more likely to understand and interpret everyday events in different ways than younger people

Karen Campbell

photographymontreal

Hitchcock

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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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