Local inhibition of GABA affects precedence effect in the inferior colliculus

Yanjun Wang; Ningyu Wang; Dan Wang; Jun Jia; Jinfeng Liu; Yan Xie; Xiaohui Wen; Xiaoting Li

doi:10.3969/j.issn.1673-5374.2014.04.013

摘要：The precedence effect is a prerequisite for faithful sound localization in a complex auditory envi-ronment, and is a physiological phenomenon in which the auditory system selectively suppresses the directional information from echoes. Here we investigated how neurons in the inferior col-liculus respond to the paired sounds that produce precedence-effect illusions, and whether their ifring behavior can be modulated through inhibition with gamma-aminobutyric acid (GABA). We recorded extracellularly from 36 neurons in rat inferior colliculus under three conditions:no injection, injection with saline, and injection with gamma-aminobutyric acid. The paired sounds that produced precedence effects were two identical 4-ms noise bursts, which were deliv-ered contralaterally or ipsilaterally to the recording site. The normalized neural responses were measured as a function of different inter-stimulus delays and half-maximal interstimulus delays were acquired. Neuronal responses to the lagging sounds were weak when the inter-stimulus delay was short, but increased gradually as the delay was lengthened. Saline injection produced no changes in neural responses, but after local gamma-aminobutyric acid application, responses to the lagging stimulus were suppressed. Application of gamma-aminobutyric acid affected the normalized response to lagging sounds, independently of whether they or the paired sounds were contralateral or ipsilateral to the recording site. These observations suggest that local inhibition by gamma-aminobutyric acid in the rat inferior colliculus shapes the neural responses to lagging sounds, and modulates the precedence effect.