Peculiarities of time patterns of discharges of single auditory neurons of mouse inferior colliculi

Abstract

Neurophysiological mapping of single neuronsof the central nucleus of the mouse inferior colliculus has revealed presence of four main groups ofneurons differing by distribution and ratio of excitatory and inhibitory inputs in frequency receptivefields [1, 2]. Among them there are “primary–like”neurons reproducing frequency tuning of the auditory nerve fibers, the “inhibitiondependent”ones with predominance of the inhibitory actionand penetrating deeply into the field of the exciting response, the “Vshaped” neurons characterized by a decrease of inhibitory inputs, and the“complex” ones that have a complex shape of receptive fields and more than one characteristic frequency [2, 3]. Study of the frequency properties ofvarious neuronal groups has allowed suggestingtheir different specialization in providing mechanism of frequency analysis of signals [1–5]. However, to get the general picture of coding of theacoustic signal parameters by the central auditoryneurons, the knowledge is necessary not only of thefrequency, but also of the temporal mechanism ofthe signal coding. In spite of the abundance of thestudies on temporal mechanism of the signal coding [6–11], its participation in the frequency processing of signals by the midbrain auditory neuronshas not been elucidated. Except for the only communication by Ehret et al. [12], there are no ordered data in the literature about temporal properties of single neurons of the auditory center ofthe mouse midbrain—about the pattern and latentperiods of responses. Correlation of impulse temporal characteristics of activity of these neuronsand of structural peculiarities of their frequencyreceptive fields has not been studied. The goal ofthe present work was to study time patterns of discharges—the patterns of responses of auditory neurons of the mouse midbrain by the method of systematic mapping of their frequency receptivefields.In this work, an extracellular recording of theimpulse activity of single neurons in the inferiorcolliculus central nucleus was performed in45 anesthetized house mice (