Effects of An 8-Week Moderate-Intensity Aerobic Exercise Intervention on Episodic Memory and Cognitive Control

Abstract

Although the effects of exercise on global cognitive function are well documented, there have been few randomized trials of aerobic exercise that focus specifically on select aspects of cognition, including episodic memory and cognitive control processes. Understanding these cognitive processes may be particularly important for individuals with major depressive disorder (MDD), as deficits in both memory and cognitive control are well recognized in MDD. PURPOSE: The primary aim was to assess the effects of an aerobic exercise intervention on episodic memory and cognitive control in individuals with and without MDD. METHODS: 48 participants (24 healthy, 24 MDD) were randomly assigned to either 8-weeks of aerobic exercise (AE) or a control group of time-matched light stretching. AE and stretching groups consisted of three weekly 30-45-min sessions per week. Depressive symptoms (BDI), peak aerobic fitness (VO2 peak), episodic memory, and cognitive control were assessed at baseline and follow-up. Episodic memory and cognitive control were assessed using behavioral and event-related brain potential (ERP) measures during old/new and modified flanker tasks. RESULTS: After 8-weeks of AE, there were significant reductions in depressive symptoms, despite no change in aerobic fitness. No significant behavioral findings were observed for the old/new task; however, ERP analyses indicated significant increases in the parietal late positive component (LPC) from pre-to-post intervention, p < .05. Improvements were observed for reaction time during the flanker task, F(1,17)=16.89, p < .001, but not accuracy. Significant increases in flanker N2 and P3 component amplitudes were observed, ps < .05. CONCLUSION: These findings suggest that 8-weeks of moderate-intensity AE has a significant influence on both episodic (recognition) memory and cognitive control processes, particularly among individuals with MDD. However, the effects were larger for cognitive control relative to recognition memory. The 8-week AE program improved select aspects of cognitive function, in addition to reducing depressive symptoms. These benefits occurred without a change in fitness, suggesting other psychobiological mechanisms of action.