Auditory Mismatch Negativity in Response to Changes of Counter-Balanced Interaural Time and Level Differences

Abstract

Interaural time differences (ITD) and interaural level differences (ILD) both signal horizontal sound source location. To achieve a unified percept of our acoustic environment, these two cues require integration. In the present study, we tested this integration of ITD and ILD with electroencephalography (EEG) by measuring the mismatch negativity (MMN). The MMN can arise in response to spatial changes and is at least partly generated in auditory cortex. In our study, we aimed at testing for an MMN in response to stimuli with counter-balanced ITD/ILD cues. To this end, we employed a roving oddball paradigm with alternating sound sequences in two types of blocks: (a) lateralized stimuli with congruently combined ITD/ILD cues and (b) midline stimuli created by counter-balanced, incongruently combined ITD/ILD cues. We observed a significant MMN peaking at about 112–128 ms after change onset for the congruent ITD/ILD cues, for both lower (0.5 kHz) and higher carrier frequency (4 kHz). More importantly, we also observed significant MMN peaking at about 129 ms for incongruently combined ITD/ILD cues, but this effect was only detectable in the lower frequency range (0.5 kHz). There were no significant differences of the MMN responses for the two types of cue combinations (congruent/incongruent). These results suggest that—at least in the lower frequency ranges (0.5 kHz)—ITD and ILD are processed independently at the level of the MMN in auditory cortex.

Influence of Audiovisual Training on Horizontal Sound Localization and Its Related ERP Response

“…Regarding the ERP study on sound localization, previous studies have found that changes of spatial cues (ITD, ILD, spectral cues) could evoke MMN response (100–130 ms) in auditory cortex (Altmann et al, 2017a , b ; Frey et al, 2017 ). In the present study, neurophysiological results did not show significant changes in terms of the early ERP components of N1 either between pre- and post-tests or between audiovisual and auditory only training groups.…”

BrainKilter: A Real-Time EEG Analysis Platform for Neurofeedback Design and Training

“…Previous studies have shown that the use of MMN neurofeedback training can improve a subject's ability to discriminate between two defined frequencies; however, the auditory discriminative abilities of healthy people have not been discussed. MMN steady induction traditionally requires more than 200 stimulation events (containing both standard and deviant) [20]. In the previous neurofeedback protocol, 20 stimulation events were adopted to calculate real-time MMN.…”