Age effects on brain activity associated with episodic memory retrieval. An electrophysiological study.

Electrophysiological correlates of episodic memory retrieval (recollection) were investigated in a young (18-30 years) and an older group (62-79 years) of healthy subjects (n = 16 per group). At study, subjects listened to words spoken in either a male or a female voice, and were instructed to perform one of two tasks depending on the voice in which the item was spoken. At test, subjects made initial old/new judgements to visually presented words and, for words judged old, either indicated in which voice they had heard the word at study (source task), or whether the 'remembered' or 'knew' they had heard the word at study ('remember/know' task). The accuracy of the initial recognition decision did not differ between the two groups. However, young subjects were significantly more accurate in their source judgements than the older group. The magnitudes and topographical distributions of differences between event related potentials to successfully recollected words and new words were indistinguishable for the two tasks. These event-related potential effects were also equivalent in magnitude and scalp topography in the two age groups, the only difference between the groups being a relative delay in the onset of the effects at some electrode sites in the older subjects. These findings are consistent with the proposal that the processes supporting episodic retrieval, including those dependent upon the prefrontal cortex, are relatively unaffected by advancing age.