Effects of Mild Traumatic Brain Injury on Auditory Function in a Mouse Model

Abstract

Traumatic brain injury negatively impacts auditory processing including difficulty in hearing in background noise. In this study we used behavioral and electrophysiological outcomes to examine the effects of mTBI on perceptual auditory disorders and change in behavioral responses overtime following injury. Subjects were 16 (equal gender), 6 month old CBA/CaJ mice. All experimental protocols were approved by the University of South Florida Institutional Animal Care and Use Committee (IACUC). Mice were exposed to either sham or to mTBI administered using a controlled cortical impactor. Auditory behavioral responses were measured using acoustic startle response (ASR). Auditory brainstem response (ABR) audiograms from 8 to 32 kHz were used to measure hearing function. A gap-in-noise paradigm (70 dB SPL markers with gap durations of 2 to 64 ms) was also used to assess temporal processing. All TBI animals showed symptoms immediately following TBI: motor lethargy, poor appetite and mild weight loss, with recovery seen within 3 days. Behavioral and electrophysiological assessments were completed at 3, 7, 14, 28, 35, 45, and 90 days post-TBI. Three days post-TBI, ASR functions were comparable between TBI and sham groups. For ABRs, there was a significant decrease in the amplitudes of P1 (22%) and P4 (30%), and an increase in P4 latency in the mTBI mice. These findings indicate that mTBI can result in significant long term deficits of auditory processing and the mouse model may prove to be a translational model for understanding the pathology and treatment of mTBI-induced auditory dysfunction.