EFFECTS OF AEROBIC EXERCISE ON FUNCTIONAL CONNECTIVITY OF PREFRONTAL CORTEX IN MCI: RESULTS OF A RANDOMIZED CONTROLLED TRIAL

The results of several clinical trials provide mounting evidence to support aerobic exercise benefits for the brain in healthy older adults. However, the effects of exercise on brain in adults with amnestic mild cognitive impairment (aMCI) are not as well understood. Previously, our group presented data showing that 6 months of aerobic exercise improved executive function, increased cerebral blood flow to prefrontal cortex, and reduced phosphorylated tau levels in cerebrospinal fluid. Given these previous findings, we hypothesized that functional connectivity in prefrontal cortex would be altered after the intervention. The purpose of this analysis was to use graph theory methods to assess networks associated with prefrontal cortex before and after an aerobic exercise intervention. Participants with adjudicated aMCI were randomized to either 6 months of aerobic exercise (n=37) or a stretching control group (n=34). Aerobic training consisted of treadmill walking at 70–80% of heart rate reserve, four days/week. All participants completed cognitive testing before and after the intervention, and a subset completed MRI neuroimaging including resting state fMRI (aerobic n=16, stretch n=19). Graph theory-based methods were used to characterize brain network organization and compare data across the aerobic and stretching groups. Between-group comparisons of community structure were made using permutation with a significance level of p<0.05. Comparison of whole-brain averages were made in SAS. The community structure of prefrontal cortex was comparable between groups at baseline. The aerobic exercise intervention resulted in a significant (p=0.05, Figure) change in the prefrontal community, but there was no significant change in the control group. The community structure change was driven primarily by a dramatic increase in the consistency of the connectivity in prefrontal regions. The spatial pattern of the community (i.e. the brain regions that belonged to the community) did not change. There were no group differences in whole-brain average path length, clustering, or degree.