Roles of GABAergic inhibition for the binaural processing of multiple sound sources in the inferior colliculus.
This review explores the questions of how spike trains that originate from lower auditory nuclei interact in the inferior colliculus to produce an output that synthesizes the information from all these sources. The focus is on the processing of interaural intensity disparities, the cues animals use to localize high-frequency sounds, and the roles of the lateral superior olives and the dorsal nucleus of the lateral lemniscus (DNLL) in shaping the binaural properties of their targets in the inferior colliculus. The main points advanced in this review are 1) that the DNLL shapes the binaural properties of many inferior collicular neurons, 2) that the inhibitory inputs to the DNLL allow it to act as a switch that can be turned on or off with appropriate acoustic stimulation, and 3) that when two or more stimuli are presented, each from a different region of space, the first stimulus can switch the DNLL to its off position. The consequence of the initial stimulus is that stimuli that follow shortly thereafter cannot activate the DNLL, and thus the binaural properties of those collicular cells that receive inhibition from the DNLL are changed. The implications of this switching action are that the location of the initial signal is coded appropriately, whereas the coding of the location of the signal or signals that follow the initial signal is smeared, and consequently, those following signals cannot be accurately localized. In short, it is proposed that the DNLL plays a pivotal role in the way the locations of multiple sound sources are coded by the auditory system.
Pollak
G D
GD
Department of Zoology, University of Texas at Austin 78712, USA.
D001640:Bicuculline / Q000494:pharmacology*; D017626:Cochlear Nucleus / Q000187:drug effects; D018756:GABA Antagonists / Q000494:pharmacology*; D006801:Humans; D007245:Inferior Colliculi / Q000187:drug effects*; D013017:Sound Localization; D013331:Strychnine / Q000494:pharmacology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism* / Q000494:pharmacology*
D018756:GABA Antagonists; D005680:gamma-Aminobutyric Acid; D013331:Strychnine; D001640:Bicuculline