Encoding of frequency-modulation (FM) rates in human auditory cortex.

Hidehiko Okamoto,Ryusuke Kakigi

doi:10.1038/srep18143

Abstract

Frequency-modulated sounds play an important role in our daily social life. However, it currently remains unclear whether frequency modulation rates affect neural activity in the human auditory cortex. In the present study, using magnetoencephalography, we investigated the auditory evoked N1m and sustained field responses elicited by temporally repeated and superimposed frequency-modulated sweeps that were matched in the spectral domain, but differed in frequency modulation rates (1, 4, 16, and 64 octaves per sec). The results obtained demonstrated that the higher rate frequency-modulated sweeps elicited the smaller N1m and the larger sustained field responses. Frequency modulation rate had a significant impact on the human brain responses, thereby providing a key for disentangling a series of natural frequency-modulated sounds such as speech and music.

Highlights

Frequency-modulated sounds play an important role in our daily social life
The ability of humans to identify Frequency modulation (FM) rates plays an important role in our daily social life; the neural mechanisms underlying FM encoding remains elusive in the human auditory cortex
FM sweeps in cats more dominantly activated non-primary auditory areas than the primary auditory cortex in a modulation rate-dependent manner[20,21,22]; the effect of the FM rates on the neural activity remains elusive in the human auditory cortex

Summary

Introduction

Frequency-modulated sounds play an important role in our daily social life It currently remains unclear whether frequency modulation rates affect neural activity in the human auditory cortex. In the present study, using magnetoencephalography, we investigated the auditory evoked N1m and sustained field responses elicited by temporally repeated and superimposed frequencymodulated sweeps that were matched in the spectral domain, but differed in frequency modulation rates (1, 4, 16, and 64 octaves per sec). In the present study we investigated the auditory evoked responses elicited by temporally repeated and superimposed FM sweeps (Figs 1 and 2) This experimental design allowed us to measure the brain activity elicited by FM sweeps that were matched in the spectral domain, but differed in the frequency modulation rates

Objectives

Methods

Results

Conclusion