Alpha suppression as a neural marker of task demands in voluntary vs involuntary retrieval in older and younger adults
Henderson, Sarah Elizabeth
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Voluntary episodic memory relies on intentionally controlled retrieval, while involuntary episodic memory comes to mind automatically. Consistent with findings of reduced cognitive control with age, recent work suggests that voluntary memory declines with age while involuntary memory is relatively preserved. However, the neurophysiology underlying these age differences has yet to be established. The current study used EEG to test 31 young and 35 older adults during voluntary vs. involuntary retrieval (manipulated between-subjects). Participants first encoded sounds, half of which were paired with pictures, the other half unpaired. EEG was then recorded as they listened to the sounds, with participants in the involuntary group performing a sound localization task, and those in the voluntary group additionally attempting to recall the associated pictures. Participants later retrospectively reported which sounds brought the paired picture to mind during the sound task. Older adults said they remembered as many pictures as young adults, but their objective memory was lower on a final cued recall test. For the EEG analysis, older adults showed greater alpha event-related desynchronization (ERD; a neural marker of memory reactivation) for paired than unpaired sounds at occipital sites, possibly reflecting visual reactivation of the associated pictures. Young adults did not show memory-related alpha ERD effects. However, young adults did show greater alpha ERD during voluntary than involuntary retrieval at frontal and occipital sites, while older adults showed pronounced alpha ERD (indicative of effortful retrieval) regardless of condition. These data suggest that alpha ERD can be used as a neural marker of memory in older adults; however, a more naturalistic paradigm may be required to study true involuntary memory with age.