Representation of whispered word-final stop consonants in the auditory nerve.

Recent physiological results from the auditory nerve suggest that specific response patterns for word-initial /d/ and /t/ are present across acoustic variations. In this study, single cell recordings from the auditory nerve of anesthetized chinchillas in response to the stop consonants /d/ and /t/ presented in a variety of acoustic contexts were analyzed. Consonants had variable word positions, vowel contexts, types of phonation, and speakers. The response patterns from individual auditory nerve fibers did not reliably differentiate the consonants /d/ and /t/. Global average peristimulus time histograms (GAPSTs) contained invariant patterns for all tokens of each word-final consonant, regardless of context. Ensemble responses to word-final consonants had similarities in their temporal patterns to those in GAPSTs for word-initial consonants. The similar representations in the ensemble auditory nerve response for consonants with different acoustic content suggest a possible substrate for perceptual normalization. Both invariant and variable elements of speech can be computed from the ensemble response of the auditory nerve.