Reduced cortical excitability is associated with head impact severity and cognitive symptoms in adolescent football players

American tackle football is associated with high rates of concussion, leading to neurophysiological disturbances and debilitating clinical symptoms, but previous investigations have largely ignored aperiodic neurophysiological activity. In this study, we use pre- and post-season resting-state magnetoencephalography (MEG) to examine whether concussion during a season of football is related to changes in neurophysiology and whether any such changes are associated with clinical outcomes. Concussion was associated with increased aperiodic exponents in superior frontal cortices, indicating a relative reduction in cortical excitability, which accounted for effects on raw delta and gamma power and was associated with worse cognitive concerns across participants. Subtler effects of non-concussive head-impact exposure on neurophysiology were similar to those of concussion. These findings indicate that concussion alters the excitability of the cortex, similar to much more subtle effects of non-concussive exposure.