Cognitive ageing and the role of the frontal lobes in prospective memory and planning
A recent theory postulates that the cognitive functions associated with the frontal lobes are likely to selectively deteriorate with age (West, 1996). In line with this theory, it was predicted that an age-related decline in measures of prospective memory and planning would be observed. In order to investigate this hypothesis, a series of five experiments were conducted using groups of young, middle aged and older normal participants. In Experiment 1, participants were asked to follow a recipe while remembering to do various prospective memory tasks at the same time. Older participants performed significantly worse on all measures of prospective memory. Significant age differences in measures of planning were observed in the computerised &'34;Tower of London&'34; planning task in Experiment 2. In Experiment 3, participants were given an open-ended planning task involving allocating a list of tasks to three friends. Older participants made significantly more overall planning errors. In Experiment 4, few age differences were observed in general executive function. In Experiment 5, the role of attention in prospective memory and planning was examined. Older participants performed significantly worse than the younger participants at the prospective memory and planning tasks. Speed of information processing was more highly associated with performance on the planning and prospective memory tasks than the attentional measures. There was not enough evidence available from the two patient studies to suggest that prospective memory was differentially impaired in patients with frontal lesions. The overall results confirmed the experimental hypothesis that there is an age-related decline in prospective memory and planning. However, the extent to which these age-related declines can be attributed to selective declines in the frontal lobes remains unclear.