Ageing and episodic retrieval: using event-related potentials to compare the neural correlates of item and associative recognition in young and older adults.

Abstract

Older people commonly report problems with remembering, and behavioural studies have confirmed that memory does decline with age. Age-related deficits are particularly evident in episodic memory; however, the degree of impairment appears to be task-dependent. Compared to young adults, older adults generally perform reasonably well on simple item recognition tasks, but are markedly compromised on more complex tasks, such a s those that require memory for context. Dual process theory suggests that this pattern of ageing deficits results from an age-related decline in recollection, whilst familiarly remains relatively intact. This thesis reports a series of event-related potential (ERP) studies conducted to examine the effect of ageing on the neural correlates of simple item recognition and more complex associative recognition. Behaviourally, as anticipated, the young outperformed the elderly, particularly in associative recognition. Electrophysiologically, the age-related reduction of the left parietal effect in item recognition appeared to support the dual process view that recollection becomes compromised as people grow older. Likewise, an early right frontal component, evident in both item and associative recognition, may reflect the preservation of familiarity in elderly adults. However, the ERP data also suggest that dual process theory may represent an oversimplification of episodic memory age decline. While the presence of a left parietal sam e/rearranged difference in young adults was interpreted as evidence of the adoption of a target-specific recollection strategy in associative recognition, the modulation's absence in older adults suggests that they are unable to similarly inhibit the retrieval of goal-irrelevant information. Moreover, the older participants also demonstrated widespread left-sided negative activations that may represent two components: First, the fronto-central negativities elicited by both tasks may index the compensatory operations recruited by older adults to maximise their performance. Second, a central/posterior negativity in item recognition, which strongly resembled a modulation that had been previously observed in source memory ageing studies, was interpreted as reflecting the task-irrelevant retrieval of contextual information.