Auditory evoked fields elicited by spectral, temporal, and spectral–temporal changes in human cerebral cortex

Hidehiko Okamoto

doi:10.3389/fpsyg.2012.00149

Abstract

Natural sounds contain complex spectral components, which are temporally modulated as time-varying signals. Recent studies have suggested that the auditory system encodes spectral and temporal sound information differently. However, it remains unresolved how the human brain processes sounds containing both spectral and temporal changes. In the present study, we investigated human auditory evoked responses elicited by spectral, temporal, and spectral–temporal sound changes by means of magnetoencephalography. The auditory evoked responses elicited by the spectral–temporal change were very similar to those elicited by the spectral change, but those elicited by the temporal change were delayed by 30–50 ms and differed from the others in morphology. The results suggest that human brain responses corresponding to spectral sound changes precede those corresponding to temporal sound changes, even when the spectral and temporal changes occur simultaneously.

Highlights

Natural sounds such as bird songs or human speech are complex and time-varying signals
Examples of individual magnetic field waveforms obtained in each experimental condition (SC, temporal sound www.frontiersin.org changes (TC), and spectral–temporal change (STC)) and the difference waveforms between STC and SC and between STC and TC are shown in Figure 3 and 4
The results of the present study demonstrated that the neural responses elicited by spectral–temporal sound changes (STC) were very similar to those elicited solely by SC

Summary

Introduction

Natural sounds such as bird songs or human speech are complex and time-varying signals. Sound waves entering the cochlea cause different parts of the basilar membrane to vibrate in a frequency-dependent manner, and thereby spectral sound information is systematically translated into a place code (cochleotopy or tonotopy; Robles and Ruggero, 2001). This place coding is maintained throughout the central auditory pathway (Reale and Imig, 1980; Schreiner and Langner, 1988). It is reasonable to assume that the spectral fine-structure is not coded by the firing patterns of neurons in the human auditory cortex

Methods

Results

Conclusion