Effects of the binaural auditory filter in the human brain

Abstract

The effects of the binaural auditory filter in the human auditory cortex were examined by auditory-evoked magnetic fields. Two tones with different frequency separations, which were presented dichotically to the left and right ears, were used as the sound stimuli, with all signals presented at sound pressure level of 60 dB. The results indicated that the N1m amplitudes were approximately constant when the frequency separation was less than 100 Hz; however, the N1m amplitudes increased with increasing frequency separation when the frequency separation was greater than 200 Hz. These findings indicate that binaural auditory filter-like behavior might be reflected in N1m amplitudes.

Effects of center frequency on binaural auditory filter bandwidth in the human brain

“…The estimated binaural critical bandwidth was approximately 10-20% of the center frequency. This is consistent with the earlier finding of an estimated critical bandwidth of 96 Hz, calculated using similar methods to those in this study, when the center frequency was 1000 Hz [10]. For the diotic condition, the effects of frequency separation of a two-tone complex and a three-tone complex [quasifrequency-modulation (QFM)] on the AEFs have also been examined when the center frequency was 1000 Hz [15].…”

“…The averaged amplitude of the N1m component from the left and right hemispheres was used for this fitting, because the main effect of hemisphere on the N1m amplitude was not significant. The estimated data in this study and an earlier study [10] were combined and fitted to an equation (Fig. 3).…”

“…However, there is little evidence of physiological correlates of the critical bandwidth under binaural and dichotic listening conditions. Our earlier study indicated that the amplitudes of the N1m components of auditory-evoked fields (AEFs) were approximately constant when the frequency separation was less than 100 Hz (10% of the center frequency); however, the N1m amplitudes increased with increasing frequency separation when the frequency separation was greater than 200 Hz (20% of the center frequency), when the center frequency was 1000 Hz [10]. This estimates that the binaural auditory filter bandwidth is 100-200 Hz at a center frequency of 1000 Hz.…”

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

“…First, in order to estimate binaural auditory filter bandwidth, two tones with different frequency separations and center frequencies, which were presented dichotically to the left and right ears, were used as the sound stimuli and AEFs were evaluated. The results indicated that the N1m amplitudes are approximately constant when the frequency separation is less than 10-20% of the center frequency; however, the N1m amplitudes increase with increasing frequency separation when the frequency separation is greater than 10-20% of the center frequency (Soeta & Nakagawa, 2007;Soeta et al, 2008). These results indicate that binaural auditory filter bandwidth is approximately 10-20% of the center frequency.…”

Effects of binaural beats and isochronic tones on brain wave modulation: Literature review

“…Brain waves consist of rhythmic patterns of neuronal activity or synchronized electrochemical pulses from groups of neurons in the central nervous system (CNS) 1 . There are several well-established brainwave range patterns: gamma (30-70 Hz), beta (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30), alpha (8)(9)(10)(11)(12)(13), theta (4-8 Hz), and delta (1-4 Hz) 2 . Each one of these frequency bands has been correlated with different states of consciousness, such as awake, relaxed, rapid eye movement (REM) sleep, as well as non-REM sleep stages 3 .…”