Blast exposure in the military and its effects on sensory and cognitive auditory processing

Blast-induced traumatic brain injury (TBI) and hearing loss are the two most common types of injuries sustained by military personnel while serving in the U.S. Global War on Terrorism. Recently several VA audiology clinics have reported active duty service members complaining of having problems communicating in noisy listening environments despite having normal to near-normal pure tone thresholds. In addition to standard clinical measures, we used electroencephalography (EEG) to determine whether damage to suprathreshold responding auditory nerve fibers in the sensory periphery and/or trauma to cortical regions associated with attention and working memory were responsible for the reported listening complications. In separate auditory and visual selective attention tasks, behavioral and neural measures suggest no evidence of long term neurotrauma affecting normal cognitive function. We found while absolute measures of auditory brainstem encoding varied greatly in all study subjects, comparisons of how the envelope following response (EFR) changes with modulation depth hint at differences between blast and non-blast exposed service members. These findings are consistent with audiometric threshold and distortion product otoacoustic emission data that show subtle differences between groups within clinically defined normal limits. Taken together these results suggest subclinical differences in audiometric measures might explain differences in suprathreshold listening. Blast-induced traumatic brain injury (TBI) and hearing loss are the two most common types of injuries sustained by military personnel while serving in the U.S. Global War on Terrorism. Recently several VA audiology clinics have reported active duty service members complaining of having problems communicating in noisy listening environments despite having normal to near-normal pure tone thresholds. In addition to standard clinical measures, we used electroencephalography (EEG) to determine whether damage to suprathreshold responding auditory nerve fibers in the sensory periphery and/or trauma to cortical regions associated with attention and working memory were responsible for the reported listening complications. In separate auditory and visual selective attention tasks, behavioral and neural measures suggest no evidence of long term neurotrauma affecting normal cognitive function. We found while absolute measures of auditory brainstem encoding varied greatly in all study subjects, comparisons of how the ...