Neural and behavioral evidence supporting the relationship between habitual exercise and working memory precision in healthy young adults

Abstract

Introduction: Working memory (WM) is a well-known fundamental ability related to various high-level cognitive functions, such as executive functioning, decision-making, and problem-solving. Although previous studies have posited that chronic exercise may improve cognitive functions, its underlying neural mechanisms and whether habitual exercise is associated with individual WM ability remain unclear.

Methods: In the current study, 36 participants reported their habitual physical activity through the International Physical Activity Questionnaire (IPAQ). In addition to assessments of intelligence quotient (IQ), WM storage capacity (K score), and visuomotor coordination capacity, electroencephalogram (EEG) signals were recorded while the participants performed a WM precision task fusing conventional visual and motor retrospective cue (retro-cue) WM tasks.

Results: We found that greater amounts of and higher frequencies of vigorous-intensity exercise were highly correlated with smaller recall errors in the WM precision task. Contralateral delay activity (CDA), a well-known WM-related event-related potential (ERP) component evoked by the valid retro-cue, predicted individual behavioral recall error. Participants who met the medium or high level of IPAQ criteria (the regular exercise group) showed smaller behavioral recall error and larger CDA than participants who did not meet the criteria (the irregular exercise group). The two groups did not differ in other assessments, such as IQ, WM storage capacity, and visuomotor coordination ability.

Discussion: Habitual exercise was specifically correlated with individual differences in WM precision, rather than IQ, WM storage capacity, and visuomotor coordination ability, suggesting potential mechanisms of how modulations of chronic exercise improve cognition through visual and/or motor WM precision.

Keywords: contralateral delay activity; habitual exercise; retrospective cue; working memory precision; working memory storage capacity.

Figure 1

Examples of trial schedule and experimental design. The number of valid cues and neutral cues were equal. Participants needed to rotate the illusory orientation of the two dots on the probe ring to the orientation of the target bar, i.e., the bar in the encoding phase with the same color as the probe ring. ITI, intertrial interval.

Figure 2

The trial-averaged recall error and RT of the two groups. (A) The recall error of the regular and irregular exercise groups in the neutral and valid cue conditions. The horizontal bars indicate the averaged values across participants. Each dot marks a participant. Same below. (B) The RT of the regular and irregular exercise groups in the neutral and valid cue conditions.

Figure 3

Event-related potential (ERP) waveforms averaged across contralateral and ipsilateral electrodes in the two exercise groups. (A) Averaged ERPs at contralateral and ipsilateral electrodes of the regular and irregular exercise groups in neutral and valid cue conditions. The horizontal dotted line indicates 0 μV, and the vertical dotted line indicates the time of retro-cue onset. The rectangular area is the time window (800–1,300 ms) for CDA amplitude calculation. (B) Topographic maps of contralateral-minus-ipsilateral difference waves (800–1,300 ms after retro-cue onset) of regular and irregular exercise groups in neutral and valid cue conditions. The white dots are the electrodes (P3/4, P5/6, P7/8, PO5/6, and PO7/8) for ERP analysis. (C) Mean amplitudes of the difference waves between 800 and 1,300 ms after retro-cue onset of regular and irregular exercise groups in neutral and valid cue conditions. Error bars represent standard errors of the mean. ^**p < 0.010, ^***p < 0.001.

Figure 4

Spearman correlation between recall error in the valid cue condition and CDA amplitude and the total amount of exercise in the full sample (n = 30). (A) The higher the rank is, the larger the CDA amplitude and recall error. (B) The higher the rank, the larger the total amount of exercise and recall error. ^*p < 0.050.