The Effects of Repetitive, Subconcussive Impacts on Electrophysiological Measures of Attention and Information Processing Speed

Mild traumatic brain injury (mTBI) is a growing worldwide concern. Nowhere is this concern more apparent than in contact and collision sports such as boxing and football, where repeated blows to the head are an inherent part of the sport. The literature on the detrimental effects of sustaining mTBI(s) is robust and the evidence suggests potential long-term consequences in the area of attention, memory and information processing speed.;However, little research has been done on the effects of repetitive, subconcussive impacts on overall brain function. Several recent neuroimaging and event-related potential studies point towards these impacts as contributing to brain damage that is often attributed to mTBI(s). Standard neuropsychological tests appear to be insensitive to the effects of repetitive, subconcussive impacts, but the P300 response may offer a reliable method of measurement due to its ability to detect subtle cognitive deficits that may present beyond the level of behavioral tests.;In the present study, auditory evoked P300 responses, collected in the presence of a visual distracter, were examined pre- and post- season during a single, collegiate level football season (Division I Football Bowl Subdivision) and pre- and post-tournament during a three-day charity boxing tournament in 14 young adult athletes. Additional comparisons were made with a group of third and fourth year Division I Football Bowl Subdivision players. The goal of the study was to assess the feasibility of using the auditory P300 response to measure subtle changes in cognitive function that may occur as the result of repeated exposure to subconcussive impacts in contact sports over time.;Results indicate there was no difference in P300 amplitude or latency between pre- and post-season or tournament measures. However, group differences were noted at certain electrode regions when the two experimental groups were compared to the third and fourth year players. Specifically, third and fourth year players had smaller P300 amplitudes. Behavioral measures (count accuracy, reaction time) were not affected over time and did not differentiate by group.;Taken together, these results suggest exposure to subconcussive impacts over the course of a short time frame does not negatively affect brain function, but subtle difficulties with attentional resource allocation abilities may develop after multiple seasons of exposure. The lack of a difference in behavioral performance coupled with reduced P300 amplitudes suggest the effects of repetitive head impacts may appear in neurophysiological processing before manifesting in the form of behavioral symptoms. But, longitudinal studies over the course of several years are necessary before definitive conclusions can be drawn.