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Open Access Research article

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

Hidehiko Okamoto12, Ryusuke Kakigi1, Atsuko Gunji13 and Christo Pantev2*

Author Affiliations

1 Department of Integrative Physiology, National Institute for Physiological Sciences, Myodaiji, Okazaki, Japan

2 Institute for Biomagnetism and Biosignalanalysis, University of Muenster, Münster, Germany

3 Department of Developmental Disorders, National Center of Neurology and Psychiatry, Tokyo, Japan

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BMC Neuroscience 2007, 8:33  doi:10.1186/1471-2202-8-33

Published: 17 May 2007

Abstract

Background

Decrements 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.

Results

Three-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.

Conclusion

The 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.