Responses of cochlear nucleus units recorded from chinchillas trained to discriminate iterated rippled noise from flat-spectrum noise

Abstract

Behavioral responses obtained from chinchillas using a stimulus generalization paradigm show that the perception of pitch strength is dependent on the stimuli used for training. When animals are trained to discriminate a cosine-phase harmonic tone complex (COS) from a flat-spectrum, wideband noise (WBN), generalization gradients indicate that animals rely primarily on temporal information in the envelope. Gradients from animals retrained to discriminate infinitely iterated rippled noise (IIRN) from WBN indicate animals rely more on information in the fine structure. Thus, chinchillas learn to use the information in the fine structure when trained with an appropriate stimulus. In order to begin to examine whether there exists a neural correlate of this learning at the level of the cochlear nucleus, single-unit responses to IIRNs and WBN were recorded from three anesthetized chinchillas that had received considerable behavioral training in discriminating IIRNs from WBN. Preliminary data were obtained for 19 single units consisting of primarylike, chopper, and onset response types. All-order interspike-interval histograms obtained for IIRNs and WBN were qualitatively similar to those obtained from naive, untrained animals for each unit type. Quantitative comparisons among units recorded from trained and untrained animals will be presented. [Work supported by NIDCD R01 DC005596.]