Differences in EEG oscillations between normal aging and mild cognitive
impairment during semantic memory retrieval
Abstract
Semantic memory remains relatively stable with normal cognitive aging
and declines in early stages of neurodegenerative disease. We measured
electroencephalography (EEG) oscillatory correlates of semantic memory
retrieval to examine the effects of normal and pathological aging.
Twenty-nine cognitively healthy young adults (YA), 22 cognitively
healthy aging adults (HA), and 20 patients with mild cognitive
impairment (MCI) completed a semantic memory retrieval task with
concurrent EEG recording in which they judged whether two words
(features of objects) led to retrieval of an object (retrieval) or not
(non-retrieval). Event-related power changes contrasting the two
conditions (retrieval vs. non-retrieval) within theta, alpha, low-beta,
and high-beta EEG frequency bands were analyzed across time to examine
normal aging (YA versus HA) and pathological aging effects (HA versus
MCI). Though no behavioral differences between the cognitively healthy
groups were observed, we found later theta and alpha power differences
between conditions only in YA, and a high-beta power difference between
conditions only in HA. For pathological aging effects, we found reduced
accuracy in MCI. While we found different EEG patterns of early beta
power differences between conditions in MCI compared to HA, a low-beta
power difference between conditions was found only in HA. We conclude
that the aging brain relies on faster (beta) oscillations during the
semantic memory task. With pathological aging, retrieval accuracy
declines and patterns of beta oscillation changes. The findings improve
understanding on age-related neural mechanisms underlying semantic
memory and have implications for early detection of pathological aging.