The dynamics of brain frequency bands and response to neuromodulation during cognitive testing in rugby sevens athletes throughout a sports season

Recent studies have demonstrated changes in athletes brain imaging across a competitive season due to repeated head impacts during collision sports. However, there is no data reporting cortical activity in elite female rugby sevens players. There is scant literature on the effects of high-definition (HD)-transcranial direct current stimulation (tDCS) on cortical activity responses at different time points (TP) across the competitive season on the responsiveness of spectral band frequencies for HD-tDCS stimulation. This study examined the cortical activity of elite female rugby sevens players prior to pre-season (TP1) and following five months of training and competition (TP2), and the acute effects of HD-tDCS on cortical activity parameters. For each TP, the squad was randomly allocated to the HD-tDCS sham or the HD-tDCS anodal (active) stimulation groups. The Stroop task was performed for approximately 15 min prior to HD-tDCS (Stroop task-PRE). Following completion of the Stroop task-PRE, participants received 20-minutes of HD-tDCS stimulation and then performed the Stroop task (Stroop task-POST). A diminished responsiveness of cortical activity to the perturbation (HD-tDCS) for TP2 (vs. TP1) was observed, with cortical rhythms exhibiting a relative decline in faster bands (alpha, beta, and gamma), while slower bands (delta and theta) increased its proportional contribution to cortical activity. This discovery implies a potential alteration in the neural substrate’s responsiveness to neuromodulation, likely influenced by the cumulative effects of repeated head impacts. The diminished responsiveness to HD-tDCS prompts significant considerations for the application of neuromodulation techniques in athletes participating in contact/collision sports.