To examine differences in EEG oscillations between normal cognitive aging versus pathological aging during semantic memory retrieval.

Semantic memory remains relatively stable with normal cognitive aging and its decline might be an indicator of a neurodegenerative disease. Studying EEG correlates of semantic retrieval could provide early markers of neurodegeneration.

Twenty-nine young adults (YA: 21.3 years), 22 healthy aging adults (HA: 63.9 years), and 20 patients with mild cognitive impairment (MCI: 67.8 years) participated. We recorded EEG while one completed a semantic task in which one was asked to judge whether two words led to retrieval of an object (retrieval, R) or not (non-retrieval, NR). Using Morlet wavelet time-frequency decomposition, event-related power changes within theta (4-8Hz), alpha (8-12Hz), low-beta (12-20 Hz), and high-beta (20-30 Hz) EEG frequency bands were measured. Power data contrasting R vs NR trials were analyzed separately to compare (1) YA versus HA (normal aging effects) and (2) HA versus MCI (pathological aging effects) using independent t-tests (permutations N = 2000; significance level at FDR of 0.05).

Brain responses transition from slower (alpha, theta) to faster (beta) activity with aging during semantic memory retrieval. Retrieval accuracy declines and patterns of neural oscillation change with MCI. The findings have implications for early detection of pathological aging.