Development of Tone-Burst Responses Along the Auditory Pathway in the Cat

Abstract

Microelectrodes were used to record responses evoked in the cochlear nuclei, inferior colliculus, and medial geniculate body to pure tone auditory stimulation at various stages after birth in young cats. Cortical evoked responses were recorded with the aid of macroelectrodes. The time of the earliest recordable responses to physiological stimulation does not reveal as valuable information about the maturation of the central auditory centers as such criteria as response latency, fatigability, changes in threshold, frequency spectrum, and evidence of inhibition. Our physiological results show that maturation of the auditory pathway proceeds centripetally, in accordance with some histological data. According to preliminary data, the last stage of the auditory system to become functionally mature may be the hair cell nerve ending synapse because the cochlear microphonic can be elicited by sounds and the central auditory pathways electrically stimulated before the action potential responses can be recorded.