A Biological Framework of Reduced Physical and Social Activity across the Lifespan

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For decades, we have known that being physically and socially active can have major health benefits, including the prevention of later life ill-health and the improvement of symptoms when sick. Despite these benefits, many people do not engage in regular exercise and are socially dis-engaged. Such inactivity increases as people get older, leading to significant costs to health systems across the world, as well as major personal costs to the individual.Why aren't people more active? A crucial factor that prevents an active life is motivation. People who are more motivated are more active. Even otherwise healthy people can suffer from high levels of motivation problems such as social apathy (people enjoy social interactions but simply don't have the will to engage in them) or fatigue (people who feeling exhausted after small levels of exertion). Moreover these motivational impairments increase as people get older. Yet, we understand very little about why people vary in motivation. Is there a biology of social apathy and fatigue? The overarching aim of the proposed research is to identify how differences in how certain systems in the brain work, relates to differences in how socially apathetic or fatigued people are, and to examine how changes in the brain lead to reduced motivation as we get older. To do this I will extend recent advancements in basic neuroscience that has provided a rich understanding of how the brain motivates behaviour. Within this research it has been suggested that reduced motivation might be due to a heightened sensitivity to how effortful actions are. People who are more motivated find the same actions less effortful. Here, I propose to examine how different aspects of effort sensitivity may be linked to fatigue and social apathy in healthy people as they get older. To do this, I will perform studies in healthy human volunteers using a number of techniques including brain imaging, brain stimulation and a mobile phone game, with effort sensitivity quantified using precise computational approaches. Using all of these approaches together I will be able to answer specific questions about the systems in the brain that motivate behaviour in social situations and when getting exhausted. By comparing the brain systems underlying effort sensitivity in young and older people, I will try and understand what changes in the brain may lead to higher levels of social apathy and fatigue as people get older. In summary, the key questions that the proposed research would examine are:1) Can social apathy and fatigue be characterised as increased sensitivity to different aspects of effort in healthy people? 2) Do social apathy and fatigue increase across the lifespan because of heightened effort sensitivity? 3) What systems in the brain underlie different aspects of effort sensitivity and are they linked to social apathy and fatigue? 4) Are changes in these brain systems in older adults linked to increased effort sensitivity, social apathy and fatigue? 5) Can stimulating these brain areas in a unique sample of individuals with deep brain stimulators implanted into specific brain areas provide evidence of these regions being causally involved in effort sensitivity? This work will be carried out in the Department of Experimental Psychology, at the University of Oxford. The principal investigator (Dr. Apps) will work in collaboration with a postdoctoral researcher, consultant surgeons in the Nuffield Department of Surgical Science, the Wellcome trust Centre for integrated neuroscience and a mobile brain training company.