Effects of the critical band on auditory-evoked magnetic fields

Abstract

Changes in the bandwidth affect the perceived loudness of a stimulus even when the level of the stimulus remains fixed. If the bandwidth of a sound is varied while maintaining the overall intensity, the loudness remains constant as long as the bandwidth is less than the critical bandwidth. If the bandwidth is increased beyond the critical bandwidth, the loudness increases with increasing bandwidth. Human cortical responses as a function of stimulus bandwidth were examined by recording auditory-evoked magnetic fields. The results showed that the N1m magnitudes, that is, the estimated equivalent current dipole moments, increased with increasing bandwidth when the bandwidth was increased beyond the critical bandwidth.

Complex tone processing and critical band in the human auditory cortex

“…Thus, N1m amplitudes show CB-like behavior. These findings that are based on AEF responses corroborate the results of both investigations of CB representations in the A1 of animals (Ehret and Schreiner, 1997;Fishman et al, 2000) and human studies demonstrating CB-like increases in the amplitudes of AEP and AEF components (Zerlin, 1986;Burrows and Barry, 1990;Soeta et al, 2005a).…”

“…We have previously shown that N1m amplitudes increase once the bandwidth of a bandpass noise exceeds the CBW; however, the effect was not statistically significant (Soeta et al, 2005a). Furthermore, N1m amplitudes increased with reducing bandwidth when the bandwidth was less than the CBW (Soeta et al, 2005a,b).…”

“…We have previously examined the N1m amplitudes of AEFs as a function of bandwidth of a bandpass noise with a center frequency of 1 kHz. N1m amplitudes of AEFs increased with increasing bandwidth when the bandwidth was greater than 160 Hz (Soeta et al, 2005a).…”

Effects of the binaural auditory filter in the human brain

“…Burrows and Barry [5] reported that the amplitude of Na of the AEP rapidly increased when the frequency separation of a two-tone complex increased beyond the CBW. Soeta et al [6,7] found that the N1m amplitudes of AEFs increased with increasing bandwidth when the bandwidth of bandpass noise or the frequency separation of a two-tone complex increased beyond the CBW. These studies have focused on physiological correlates of the monaural auditory filter in the human auditory cortex; however, relatively little is known about the physiological correlates of the binaural auditory filter in the human auditory cortex.…”

Neurophysiological Correlate of Binaural Auditory Filter Bandwidth and Localization Performance Studied by Auditory Evoked Fields

“…Burrows & Barry (1990) reported that the amplitude of Na of the AEP rapidly increased when the frequency separation of a two-tone complex increased beyond the CBW. Soeta et al (2005) and Soeta & Nakagawa (2006a) found that the amplitude of the N1m of AEFs increased with increasing the bandwidth of a bandpass noise or the frequency separation of a two-tone complex increased beyond the CBW. These studies have focused on physiological correlates of the monaural auditory filter in human auditory cortex; however, relatively little is known about the physiological correlates of the binaural auditory filter in the human auditory cortex.…”