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CHAPTER 5
Cognitive ageing in older workers and its impact on lifelong learning 97

the 30s but there is great individual variability depending on educational
background, and socioeconomic status (Salthouse and Ferrer-Caja, 2003).
Healthy ageing is accompanied by changes in the brain particularly in the
cerebral cortex and hippocampus. A description of these changes may provide
insight into the cognitive decline of healthy adults.

5.6. Neurobiology and cognitive ageing

One of the most obvious structural changes of the brain in normal ageing is a
decrease in brain volume and an increase in cerebral fluid in the ventricular
spaces (Deary et al., 2009). Neural degeneration accelerates in old age
particularly in the prefrontal areas that are most involved in problem-solving,
executive control and reasoning. Although brain cells do not have the ability
to regenerate, there is substantial plasticity in the adult brain. Plasticity refers
to reorganisation of cortical regions as a response to the external environment.
This means that if a brain region is injured other nearby or distant areas may
compensate for the lost functions. Brain atrophy begins in the cell bodies (grey
matter) rather than the nerve fibres (white matter) that remain relatively
preserved until about the age of 70 (Raz et al., 2004). Preservation of nerve
fibres assists in communication between distant cortical areas crucial for
execution of higher cognitive functions (Sullivan and Pfefferbaum, 2004).
Factors that affect age-related brain atrophy include hypertension,
corticosteroid levels, vascular changes and stress (Whalley et al., 2004).
Despite technological advances in brain imaging techniques, structural
changes in the ageing brain and cognitive deficits observed are only modestly
related (Hedden and Gabrieli, 2004). This surprising finding is explained in
relation to early life cognitive ability, education level and professional status
that seems to predict, if not to determine, cognitive ageing (Whalley et al.,
2004). It is also believed that the ageing brain compensates for lost cognitive
functions by recruiting other areas of the brain to take over. In other words,
brain changes are not always mapped on age-related cognitive changes.
Stern (2009) proposed the concept of cognitive reserve to explain the
discrepancy between brain damage and its behavioural manifestation. He
suggests that individual differences in processing cognitive tasks or
differences in underlying brain circuits, allow some people to cope better with
structural brain changes than others.
Particular importance has also been placed in identifying changes in the
hippocampus, a brain structure associated with memory. There is small yet