Functional Connectivity Within the Default Mode Network in Response to Exercise During Return-to-Sport Following Concussion

Abstract

The aim of this pilot study is to explore changes in EEG derived functional connectivity of the default mode network in response to physical exercise during return-to-sports (RTS) after sports related concussion (SRC). The rehabilitation of athletes with SRC is challenging. Presently, there are no objective biomarkers to predict effects of exercise during RTS. SRC associated diffuse axonal injuries predominantly affect the Default Mode Network (DMN). Assessing exercise induced changes in functional connectivity of the DMN may therefore be a potential target. Eleven athletes were examined during the early stages of RTS after SRC (age: 23.90 ± 4.81) and compared to 13 control athletes (age: 24.00 ± 4.90). Resting state 128-channel EEGs were collected before and after a progressive ergometer exercise protocol working up to 70% of the maximal heart rate. DMN connectivity was assessed by calculating the phase locking value (PLV) in 3 frequency bands (theta: 3-7, alpha: 7-13, beta: 14-25). Wilcoxon Signed Rank Tests were used to explore statistical significance between pre- and post-exercise. In SRC athletes PLV within the alpha band decreased significantly post-exercise (median [Mdn] = 0.445, interquartile range [IQR = 0.069) in comparison to pre-exercise (Mdn = 0.436, IQR = 0.047; Z = -1.956, p < 0.05), whereas no difference was observed in the control group (post-exercise [Mdn = 0.476, IQR = 0.072] compared to pre-exercise [Mdn = 0.461, IQR = 0.100; Z = -0.175, p = 0.86]). PLVs in the theta and beta band before and after exercise differed neither in the patient nor in the control group. Exercise induced changes of functional connectivity of the DMN within the alpha band were only present in post-concussed athletes and may be suitable as a potential objective marker to reflect pathophysiologic changes in further clinical studies to guide RTS.