Abstract
Although visible symptoms of mild traumatic brain injury (mTBI), commonly known as concussion, may improve rapidly, subtle neurophysiological alterations can persist. One such indicator is the speed of visual information transfer across the splenium of the corpus callosum, also known as inter-hemispheric transfer time (IHTT). We quantified IHTT in adults with mTBI and demographically-similar control participants at an initial assessment approximately 3-4 weeks after injury and again at follow-up about 10 months later. The analytic sample comprised 94 participants between the ages of 18 and 45 years, including 48 with mTBI (24 female) and 46 demographically-similar controls (22 female). IHTT was quantified directly using the P1 and N1 components of the scalp-recorded brain event-related potential (ERP). In a subset of 19 participants with mTBI (seven female) and 19 control participants (seven female), we also quantified the integrity of white matter in the corpus callosum using fractional anisotropy (FA) values derived from diffusion-tensor magnetic resonance imaging (DTI), along with volumetric measures of the corpus callosum. Participants with mTBI showed slower early visual transfer (P1 IHTT) at both initial and ten-month follow-up time points, whereas later processing (N1 IHTT) did not differ between groups. Fractional anisotropy (FA) MRI values generally showed lower FA across the corpus callosum in individuals with mTBI compared to controls, consistent with altered white matter microstructure. No volumetric differences were observed between groups or over time. The current findings suggest that neurophysiological differences in early interhemispheric visual processing and callosal microstructure are evident at both subacute and follow-up assessments, consistent with alterations observed months after injury.