Interhemispheric differences in P1 and N1 amplitude in EEG and MEG differ across older individuals with a concussion compared with age-matched controls.

We studied the effects of mild traumatic brain injury (mTBI) in an aging population. We examined visual search with event-related potentials (ERPs) and event-related fields (ERF) for a lateral color singleton focusing on the P1 and N1 in each hemisphere. Forty participants (19 mTBI and 21 controls) aged 50 to 72 performed a visual search task, while we recorded their magnetoencephalogram (MEG) with simultaneous electroencephalogram (EEG). We compared visual ERPs and ERFs and associated cortical activity estimated using MEG source localization. Relative to matched controls, participants with an mTBI had a smaller P1 in the left hemisphere and a smaller N1 in the right hemisphere. Also, mTBI participants showed inversed activation patterns across the hemispheres during the N1 in MEG compared with controls. This is the first study to investigate the impact of mTBI on neuronal source activations during early visual processing in an aging population. Results showed that when aging individuals suffer from an mTBI, there are perturbations in the amplitude and hemispheric dominance patterns in the visual P1 and N1 responses that are visible for months to years following the injury. Our findings indicate that mTBI can lead to modifications of sensory and/or perceptual responses, suggesting possible adaptive functional reorganization following mTBI.