Neural correlates of categorical perception in learned vocal communication.

Abstract

The division of continuously variable acoustic signals into discrete perceptual categories is a fundamental feature of vocal communication, including human speech. Despite the importance of categorical perception to learned vocal communication, the neural correlates underlying this phenomenon await identification. Here we report that individual sensorimotor neurons in freely behaving swamp sparrows express categorical auditory responses to changes in note duration, a learned feature of their songs, and that the neural response boundary accurately predicts the categorical perceptual boundary measured in field studies of the same sparrow population. Furthermore, swamp sparrow populations that learn different song dialects exhibit different categorical perceptual boundaries, consistent with the boundary being learned. Our results extend the analysis of the neural basis of perceptual categorization into the realm of vocal communication, while advancing the learned vocalizations of songbirds as a model for investigating how experience shapes categorical perception and the activity of categorically responsive neurons.