Cognitive ageing and the prefrontal cortex
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The prefrontal cortex (PFC) is a site which has been shown to be particularly susceptible to the ageing process. However, the PFC itself is a heterogeneous area, and recent studies have suggested that it can be split into anatomically and functionally distinct subregions. The present study investigated the differential effect of cognitive ageing on these subregions and their associated functions. Firstly, the present study investigated various psychological tasks for their regional specificity and suitability for use in ageing research. Tasks thought to preferentially recruit dorsolateral PFC regions included a Self-Ordered Pointing task and the Digit Span Backwards task. Tasks thought to preferentially recruit orbital PFC regions included a Reversal Learning task and the Faux Pas task. Tasks thought to preferentially recruit medial PFC regions included a Simon task and the AX-Continuous Performance task. The performance of younger and older individuals was then compared on the selected tasks. Age-related differences were found on both dorsolateral and orbital PFC tasks, but not on medial PFC tasks. Particular declines were observed in working memory and associative learning abilities, whilst no evidence of dysfunction was found on performance monitoring and social-emotional skills. The results support a region-specific theory of cognitive ageing whereby both dorsolateral and orbital PFC regions are most susceptible to decline, with the medial PFC relatively preserved.