Inhibitory plasticity and auditory function

Abstract

The mammalian auditory system serves many functions for an-organism throughout its life, including the spatial localization of sound sources and the recognition of behaviorally-relevant sounds. The neural circuitry underlying these various functions are not all fully elucidated, but likely involve key contributions from both subcortical as well as cortical auditory areas. While the focus has often been on the role of neural excitation within these areas, there is increasing recognition that neural inhibition and its plasticity can be just as important in shaping the function of auditory circuits. The purpose of this chapter is to use a few of the known examples of how inhibition and inhibitory plasticity subserve the functional processing of sounds to illustrate both the advances that have been made in terms of understanding mechanisms as well as the open questions remaining. The first example deals with sound localization and the brainstem circuitry that decodes binaural spatial cues. This provides one of the most detailed auditory examples of the function of inhibitory synaptic input, how inhibitory circuitry is modified by activity during development, and what potential cellular mechanisms are critical for this plasticity. The other two examples focus on the neural coding and plasticity of behaviorally relevant sounds at the cortical level. One centers on how inhibition shapes the selectivity of individual neurons for frequency modulated sounds during development, and the other on its hypothesized role in the population representation of a communication call in adults. While the cellular mechanisms underlying inhibitory plasticity are less clear in these latter cases, taken all together these examples demonstrate the importance and pervasiveness of inhibition in the functional processing of sounds.