Challenges in measuring individual differences in functional connectivity using fMRI

Susanne de Mooij, prof. Rik Henson and Dr. Rogier Kievit investigated whether and when brain connections change with age, and how these changes map onto our cognitive functioning. Using Cam-CAN data, they observed that brain structures become less connected to each other after about 55 years of age. In contrast, the relations between language, memory and reasoning stayed the same across the lifespan. Finally, they found that memory performance becomes less dependent on a white matter network (connecting the hippocampus to other parts of the brain) in later life.

Dr. Alexa Morcom and Prof. Rik Henson investigate the elevated prefrontal cortex activity that is often observed in healthy older adults despite declines in their memory and other cognitive functions. They compare two leading models of brain ageing: that the frontal cortex is either compensating for impairments elsewhere in the brain; or alternatively, that structural or neurochemical changes lead to less efficient and less specific use of resources. Using sophisticated multivariate statistical modelling of the data, the authors present evidence of the latter explanation.

Dr. Darren Price and the Cam-CAN team have shown that age-related delay of the brain’s response to visual stimulation is partly explained by damage to information-carrying white matter fibres. At the same time, age-related delay to auditory stimulation is partly explained by damage to grey matter in the auditory cortex. This study is the first to find such a relationship providing important clues regarding the biological origins of cognitive decline.

Through new funding from the EU Horizon 2020 framework, Cam-CAN will join 10 other European cohorts in the LifeBrain project to study brain change across the lifespan. The result will be a unique multinational resource of approximately 18,500 individuals that will allow investigation of cognitive and mental health throughout life. The project provides an important example of the benefits of European funding and collaboration.

Cognitive abilities change with age, but why some skills decline and others do not is still not clear. Here, Dr. David Samu and his team used data from the Cam-CAN cohort to show that responsivity of specific sets of brain networks supports different cognitive functions over the lifespan and characterizes preserved cognition in older age. These findings provide insights into why some skills are more vulnerable to age-related decline while others are preserved.

The ability to solve abstract reasoning problems, sometimes known as ‘fluid intelligence’, plays a central role in many day-to-day activities across the lifespan. Dr Rogier Kievit and colleagues at Cam-CAN have studied which mental and neural differences play a role in supporting fluid intelligence. They found that mental speed is especially important. Using MRI they also found that the strength of connections between brain regions plays an important role in supporting both mental speed and agility. Mapping these three interconnected mechanisms using mathematical models will help us better understand healthy cognitive aging.

Our ability to sense the environment is known to decline as we grow older. However, a new Cam-CAN study led by Noham Wolpe finds that the brain’s motor system compensates for this change by relying more strongly on prediction from prior experience. This adapted combination of sensory information and prediction depends on the age-related differences in grey matter integrity and functional connectivity strength in a key brain network for movement.

Many of us experience memory problems as we grow older, but did you know that different types of memory change at different rates? A recent Cam-CAN study led by Rik Henson shows how age-related differences in three types of memory depend on age-related differences in both the gray-matter integrity of key brain regions and the integrity of white-matter connections between them.

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 University of Cambridge. White matter is the tissue that connects areas of the brain and allows for information to be communicated between regions.

Understanding spoken language requires the rapid integration of information at many different levels of analysis. Given the complexity and speed of this process, it is remarkably well preserved with age. Karen Campbell and colleagues challenge the conventional approach to neurocognitive aging by showing that the neural underpinnings of a given cognitive function depend on how you test it.

To better-understand how brain flexibility influences cognition, Kamen Tsvetanov and colleagues first developed techniques to improve measurements of brain function, and then applied those techniques to show that cognitive ability is influenced by brain network flexibility in the frontal cortex. Interestingly, this relationship becomes more important with age, showing that to maintain cognition through the lifespan, brain flexibility is crucial.

Using non-invasive functional Magnetic Resonance Imaging (fMRI) and cutting-edge algorithms, Cam-CAN researchers have developed a new technique to probe the communication patterns between different parts of the human brain. We hope that this technique will give us a clearer picture of how brain connectivity changes during the ageing process, and whether this has a significant effect on cognition.