Combined and Isolated Effects of Acute Exercise and Brain Stimulation on Executive Function in Healthy Young Adults

Abstract

Abstract: Acute cognitive enhancement has been sought by healthy young individuals to improve academic and professional performance. Among several methods, physical exercise interventions and transcranial direct current brain stimulation (tDCS) have shown promise in impacting executive functions. Here, we observed a set of new findings about the causal effect of acute aerobic exercise and tDCS across three facets of executive function: Inhibition (as measured by a flanker task) was selectively impacted by acute aerobic exercise but not tDCS, whereas working memory (as measured by an n-back task) was impacted by both acute aerobic exercise and tDCS, with effects emerging on distinct processing components for each manipulation. Sustained attention (as measured by the Mackworth clock task), on the other hand, was not impacted by acute aerobic exercise or tDCS. Interestingly, no effects of combining acute aerobic exercise and tDCS emerged. We argue that understanding the unique and combined contributions of these cognitive enhancement techniques can not only contribute to a deeper mechanistic explanation in healthy individuals but also inform future research with clinical and aging populations.

Keywords: aerobic exercise; attention; inhibition; tDCS; working memory.

Figure 1

Overview of the timeline of activities at each experimental session. Session 1 activities appear in the top panel and Session 2 activities appear in the bottom panel. tDCS = transcranial direct current stimulation.

Figure 2

Correct response time standard deviations (in milliseconds, ms) on the flanker task. Bars depict average differences between Sessions 1 and 2 for each Aerobic Exercise condition (Seated vs. Exercise, leftmost and rightmost bars of each panel, respectively) and transcranial direct current brain stimulation (tDCS) condition (Active vs. Sham, in Blue and Red, respectively). Split across two panels is Congruency (Congruent vs. Incongruent, on the left and right, respectively). Error bars reflect standard errors of the mean. RT = Response Time

Figure 3

Target/nontarget discriminability (A’) on the n-back task. Bars depict average differences between Sessions 1 and 2 for each Aerobic Exercise Condition (Seated vs. Exercise, leftmost and rightmost bars of each panel, respectively) and tDCS Condition (Active vs. Sham, in Blue and Red, respectively). Split across two panels is N-Level (2-Back vs. 4-Back, on the left and right, respectively). Error bars reflect standard errors of the mean.

Figure 4

Bias to respond “Target” (Grier’s β) on the n-back task. Bars depict average differences between Sessions 1 and 2 for each Aerobic Exercise Condition (Seated vs. Exercise, leftmost and rightmost bars of each panel, respectively) and tDCS Condition (Active vs. Sham, in Blue and Red, respectively).

Figure 5

Summary of all significant main effects of Aerobic Exercise and tDCS on inhibition (flanker task), working memory (n-back task), and sustained attention (Mackworth clock task) broken down by measures associated with accuracy (i.e., average accuracy, A’, Grier’s β) and response latency (i.e., correct median response time, correct response time standard deviation (RT SD), ex-Gaussian parameters μ, σ, and τ). Green shaded boxes indicate effects in the predicted direction (see Introduction), red shaded boxes indicate effects in the opposite direction than what was predicted, and gray boxes indicate no effect.