Responses of auditory-nerve fibers to consonant-vowel syllables

The discharge patterns elicited by a set of synthesized consonant-vowel (CV) syllables were studied in the auditory nerve of the cat. The syllables, heard as /ba/, /da/, or /ga/, included a 25-, 50-, or 75-ms formant transition followed by a segment of steady-state vowel. The data were analyzed in terms of average discharge rate and in terms of the synchrony of discharges with respect to various spectral components of the stimuli. The results differ slightly from those of previous reports of the responses to vowels [Sachs and Young, J. Acoust. Soc. Am. 66, 470-479 (1979); Young and Sachs, J. Acoust. Soc. Am. 66, 1381-1403 (1979)], in that average discharge rates appear to provide more information about the spectra of formant transitions than they do about the spectra of steady-state vowels. This difference reflects changes in the spectrum of the syllable produced by movements of the formants. The synchrony of discharges, however, may provide more detailed information about the spectra of CVs than does average discharge rate. Each fiber's response at a particular peristimulus time may be characterized by the "dominant response component," the largest peak in the Fourier transform of the period histogram. The trajectories of the first three formants can be inferred from changes in the "dominant components" in a sample of fibers.