Asymmetric lateral inhibitory neural activity in the auditory system: a magnetoencephalographic study

Hidehiko Okamoto,Ryusuke Kakigi,Christo Pantev,Atsuko Gunji

doi:10.1186/1471-2202-8-33

Abstract

BackgroundDecrements of auditory evoked responses elicited by repeatedly presented sounds with similar frequencies have been well investigated by means of electroencephalography and magnetoencephalography (MEG). However the possible inhibitory interactions between different neuronal populations remains poorly understood. In the present study, we investigated the effect of proceeding notch-filtered noises (NFNs) with different frequency spectra on a following test tone using MEG.ResultsThree-second exposure to the NFNs resulted in significantly different N1m responses to a 1000 Hz test tone presented 500 ms after the offset of the NFNs. The NFN with a lower spectral edge closest to the test tone mostly decreased the N1m amplitude.ConclusionThe decrement of the N1m component after exposure to the NFNs could be explained partly in terms of lateral inhibition. The results demonstrated that the amplitude of the N1m was more effectively influenced by inhibitory lateral connections originating from neurons corresponding to lower rather than higher frequencies. We interpret this effect of asymmetric lateral inhibition in the auditory system as an important contribution to reduce the asymmetric neural activity profiles originating from the cochlea.

Highlights

Decrements of auditory evoked responses elicited by repeatedly presented sounds with similar frequencies have been well investigated by means of electroencephalography and magnetoencephalography (MEG)
We could hypothesize that the 3 s exposures to the notch-filtered noises (NFNs) altered the responsiveness of the auditory neurons activated by the subsequent test stimulus (TS) possibly via lateral connections, resulting in various N1m decrements
The present results demonstrated that lateral inhibitory effects from the lower and the higher spectral edges of NFN might be different along the auditory pathway

Summary

Introduction

Decrements of auditory evoked responses elicited by repeatedly presented sounds with similar frequencies have been well investigated by means of electroencephalography and magnetoencephalography (MEG). Some early electroencephalographic experiments observed the strongest decrement of the N1 response, when the test stimuli and the intervening tones had equal frequencies [6,7]. This decrement has been mainly argued in terms of habituation and/or refractoriness [8,9,10,11]. Both concepts mainly focus on the interaction of neural groups that are repeatedly activated by similar sound frequencies, but they did not consider the possible inhibitory interactions between different neural populations.

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