RESUMEN
INTRODUCTION: Diagnosis, assessment, and management of sports-related concussion require a multi-modal approach. Yet, currently, an objective assessment of auditory processing is not included. The auditory system is uniquely complex, relying on exquisite temporal precision to integrate signals across many synapses, connected by long axons. Given this complexity and precision, together with the fact that axons are highly susceptible to damage from mechanical force, we hypothesize that auditory processing is susceptible to concussive injury. METHODS: We measured the frequency-following response (FFR), a scalp-recorded evoked potential that assesses processing of complex sound features, including pitch and phonetic identity. FFRs were obtained on male Division I Collegiate football players prior to contact practice to determine a pre-season baseline of auditory processing abilities, and again after sustaining a sports-related concussion. We predicted that concussion would decrease pitch and phonetic processing relative to the student-athlete's preseason baseline. RESULTS: We found that pitch and phonetic encoding was smaller post-concussion. Student-athletes who sustained a second concussion showed similar declines after each injury. CONCLUSIONS: Auditory processing should be included in the multimodal assessment of sports-related concussion. Future studies that extend this work to other sports, other injuries (e.g. blast exposure), and to female athletes are needed.
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Introduction/Purpose: We tested the hypothesis that an objective measure of auditory processing reveals a history of head trauma that does not meet the clinical definition of concussion. Methods: Division I collegiate student-athletes (n = 709) across 19 sports were divided into groups, based on their sport, using prevailing classifications of "contact" (317 males, 212 females) and "noncontact" (58 males, 122 females). Participants were evaluated using the frequency-following response (FFR) to speech. The amplitude of FFR activity in a frequency band corresponding to the fundamental frequency (F0)-the voice pitch-of the speech stimulus, an outcome reduced in individuals with concussions, was critically examined. Results: We found main effects of contact level and sex. The FFR-F0 was smaller in contact athletes than noncontact athletes and larger in females than males. There was a contact by sex interaction, with the FFR-F0 of males in the contact group being smaller than the three other groups. Secondary analyses found a correlation between FFR-F0 and length of participation in contact sports in male athletes. Conclusion: These findings suggest that the disruption of sensory processing in the brain can be observed in individuals without a concussion but whose sport features regular physical contact. This evidence identifies sound processing in the brain as an objective marker of subconcussion in athletes.
RESUMEN
Speech perception depends on the auditory system's ability to extract relevant acoustic features from competing background noise. Despite widespread acknowledgement that noise exacerbates this process, little is known about the neurophysiologic mechanisms underlying the encoding of speech in noise. Moreover, the relative contribution of different brain nuclei to these processes has not been fully established. To address these issues, aggregate neural responses were recorded from within the inferior colliculus, medial geniculate body and over primary auditory cortex of anesthetized guinea pigs to a synthetic vowel-consonant-vowel syllable /ada/ in quiet and in noise. In noise the onset response to the stop consonant /d/ was reduced or eliminated at each level, to the greatest degree in primary auditory cortex. Acoustic cue enhancements characteristic of 'clear' speech (lengthening the stop gap duration and increasing the intensity of the release burst) improved the neurophysiologic representation of the consonant at each level, especially at the cortex. Finally, the neural encoding of the vowel segment was evident at subcortical levels only, and was more resistant to noise than encoding of the dynamic portion of the consonant (release burst and formant transition). This experiment sheds light on which speech-sound elements are poorly represented in noise and demonstrates how acoustic modifications to the speech signal can improve neural responses in a normal auditory system. Implications for understanding neurophysiologic auditory signal processing in children with perceptual impairments and the design of efficient perceptual training strategies are also discussed.
