Discharge patterns in auditory nerve of chinchilla to AM tones possessing low subjective pitch

Abstract

Temporal aspects of discharges in single primary auditory nerve fibers of the chinchilla were analyzed in response to computer-synthesized three-component sinusoidally amplitude modulated (AM) tones. The stimuli were of the type which, in humans, give rise to a percept of low subjective (residue) pitch. The results indicate that (a) interactions between tonal components exist in responses of units tuned to the component frequencies, the onset of these interactions corresponding roughly to the limit of the existence region for residue pitch; (b) in general, response patterns are related to the temporal features of the stimulus; (c) the responses of units tuned to the component frequencies demonstrate that a portion of activity is locked in phase to the subjective pitch frequency, even in cases producing pitch shift; and (d) units tuned to the low subjective pitch frequencies do not respond to higher-frequency AM tones at low and moderate intensity levels. Taken together, these results imply that the responses of single auditory nerve fibers to AM tones contain sufficient information for a determination of subjective pitch by either temporal fine structure or autocorrelation analysis.