Brainstem Responses to Speech in Normal Hearing and Cochlear Hearing Loss Individuals

Abstract

Studying the neural encoding of speech sounds provides insight into some of the auditory processes involved in normal communication. Auditory brainstem evoked responses to speech provide direct information about how the sound structure of a speech syllable is encoded in the auditory system. Individuals with cochlear hearing loss have consistently shown difficulties in perceiving place and manner cues of consonants. The current study aimed at determining the effect of cochlear hearing loss, stimulus presentation level (equal SL and equal SPL) on brainstem responses to speech. The ABR and FFR were recorded for the synthetic speech stimuli /da/ in 22 normals and 22 cochlear hearing loss (PTA < 55 dBHL) individuals at 80 dBnHL and 40 dB SL. Results revealed that the cochlear hearing loss showed reduced amplitude and prolonged wave latency even at equal sensational level. This effect was adverse with the increase in severity of hearing loss. The temporal fine structure coding was adversely affected with increase in the hearing loss which is reflected by the poor coding of F0 and its formant (F1)