ABSTRACT
In common with many other European countries, the United Kingdom has an aging population. The percentage of people aged 65 or older has increased from 15% in 1985 to 17% in 2010, but is set to increase rapidly to a projected 25% of the population in 2035 (Office for National Statistics, 2012). Over a similar period, the number of centenarians has increased from 2,500 in 1980 to 12,640 in 2010 (Office for National Statistics, 2011). Cognitive decline is a normal part of aging, but memory can be more sensitive to age than other aspects (Cullum et al., 2000). It is well established that as people age, although still able to recognize others as familiar, they are less likely to retrieve details such as their name or why they are familiar (the butcher-on-the-bus phenomenon). A general decline in grey matter volume, resulting from lower synaptic densities rather than cell death, is the likely cause of cognitive decline (Hedden & Gabrieli, 2004). In particular, a more rapid decline in hippocampal volume compared to associated areas is likely to result in noticeable effects on declarative or episodic memory compared to familiarity based memory. Research with both humans and animals suggests that this is due to a relative decline in functioning of the hippocampus, and that this structure is responsible for recollection, while familiarity based processes are mediated in adjacent regions such as the rhinal cortex. Selective decline in the ability to retrieve contextual information is one of the more debilitating effects of age on memory, and so it is crucial to find ways of ameliorating this process. Although many studies indicate that even brief exercise interventions can enhance performance on a number of neuro-psychological tests of cognitive function, the precise mechanisms underlying these effects are unclear. One intriguing possibility stems from evidence that physical activity produces synaptogenesis and neurogenesis in the hippocampus – which might ameliorate or reverse the age-related decline in hippocampal function
thought to impair the recollection process. In this chapter, we review the evidence for this hypothesis using data from both rodent and human studies.
