Stress-related deficits of older adults' spatial working memory: an EEG investigation of occipital alpha and frontal-midline theta activities

Abstract

Studies highlight cumulative life stress as a significant predictor of accelerated cognitive aging. This study paired electrophysiological with behavioral measures to explore how cumulative stress affects attentional and maintenance processes underpinning working memory retention. We collected electroencephalographic recordings from 60 individuals (30 older, 30 younger) reporting high or low levels of cumulative stress during the performance of a spatial Sternberg task. We measured mid-occipital alpha (8-12 Hz) and frontal-midline theta (4-6 Hz) as indicators of attentional and maintenance processes. Older, high-stress participants' behavioral performance lay significantly below than that of younger adults and low-stress older individuals. Impaired task performance coincided with reduced event-related synchronization in alpha and theta frequency ranges during memory maintenance. Electrophysiological findings suggest that older adults' reduced performance results from a stress-related impact on their ability to retain a stimulus in working memory and inhibit extraneous information from interfering with maintenance. Our results demonstrate the wide-ranging impact of cumulative stress on cognitive health and provide insight into the functional mechanisms disrupted by its influence.

Keywords: Alpha; Cognitive aging; Cumulative stress; EEG; Theta.

Fig. 1.

Box plots displaying the performance of old and young participant groups across all 4 load conditions (whiskers represent standard deviations). Young adults outperformed old adults for the high memory load conditions. *p < 0.05.

Fig. 2.

Box plots of accuracy scores displayed across age and stress groups (whiskers represent standard deviations). Old adults reporting high levels of cumulative stress performed significantly below old low-stress and young high-stress group members. *p < 0.05.

Fig. 3.

Grand average wave forms displaying the percentage change of event-related alpha desynchronization during stimulus encoding. While no age difference manifested for low (load 1) demands on WM, young participants showed higher levels of alpha ERD than old adults for high (load 4) demands on working memory. Abbreviations: ERD, event-related desynchronization; WM, working memory.

Fig. 4.

Grand average wave forms of the percentage change in alpha event-related synchronization during stimulus maintenance. Old adults with high levels of stress displayed significantly reduced mid-occipital alpha activity compared to young high-stress and old low-stress counterparts. Abbreviation: ERS, event-related synchronization.

Fig. 5.

Grand average wave forms of the percentage change in theta event-related synchronization during stimulus maintenance. Old adults with high levels of cumulative stress displayed significantly reduced levels of frontal-midline theta synchronization compared to young high-stress and old low-stress individuals. Abbreviation: ERS, event-related synchronization.