Event-related potentials and repetition priming in young, middle-aged and elderly normal subjects

Although the structure of semantic memory appears to be unaffected with increasing age, there is evidence that older adults are less efficient at accessing stored memory representations. Aging also results in a decline in the ability to use contextual information effectively, suggesting a deficit in episodic memory processes. The present experiment examines the effects of age on memory retrieval of stored representations and the use of contextual information. Event-related potentials (ERP) were recorded to immediate and delayed word repetition during a lexical decision task. Three groups of subjects were tested: young (mean = 27.3 years), middle (mean = 46.7 years) and old (mean = 67.4 years). Behavioral facilitation due to repetition did not significantly differ across groups. With increasing age, the ERP waveform showed a positive shift which began around 300-400 ms post-stimulus and was apparent across all stimulus types and response conditions. This positive shift may reflect an age-related decrease in cortical excitation. Although the onset of the ERP repetition effect was not affected by age, its duration for both immediate and delayed repetition was significantly prolonged. In the light of recent models of ERP word repetition effects, these results suggest that processes related to accessing stored representations in memory are unaffected by age. The extended duration of the repetition effect and the increase in the magnitude of the effect of delayed repetition with age suggest that aging affects processes related to the retrieval and use of contextual information in integrating a stimulus with its context.