Physiological Evidence for a Midline Spatial Channel in Human Auditory Cortex

Briley, Paul M.; Goman, Adele M.; Summerfield, A. Quentin

Abstract

Studies with humans and other mammals have provided support for a two-channel representation of horizontal (“azimuthal”) space in the auditory system. In this representation, location-sensitive neurons contribute activity to one of two broadly tuned channels whose responses are compared to derive an estimate of sound-source location. One channel is maximally responsive to sounds towards the left and the other to sounds towards the right. However, recent psychophysical studies of humans, and physiological studies of other mammals, point to the presence of an additional channel, maximally responsive to the midline. In this study, we used electroencephalography to seek physiological evidence for such a midline channel in humans. We measured neural responses to probe stimuli presented from straight ahead (0 °) or towards the right (+30 ° or +90 °). Probes were preceded by adapter stimuli to temporarily suppress channel activity. Adapters came from 0 ° or alternated between left and right (−30 ° and +30 ° or −90 ° and +90 °). For the +90 ° probe, to which the right-tuned channel would respond most strongly, both accounts predict greatest adaptation when the adapters are at ±90 °. For the 0 ° probe, the two-channel account predicts greatest adaptation from the ±90 ° adapters, while the three-channel account predicts greatest adaptation when the adapters are at 0 ° because these adapters stimulate the midline-tuned channel which responds most strongly to the 0 ° probe. The results were consistent with the three-channel account. In addition, a computational implementation of the three-channel account fitted the probe response sizes well, explaining 93 % of the variance about the mean, whereas a two-channel implementation produced a poor fit and explained only 61 % of the variance.

• Journal Article Type: Article
• Acceptance Date: Apr 26, 2016
• Online Publication Date: May 10, 2016
• Publication Date: 2016-08
• Deposit Date: Oct 7, 2021
• Publicly Available Date: Oct 7, 2021
• Journal: Journal of the Association for Research in Otolaryngology
• Print ISSN: 1525-3961
• Electronic ISSN: 1438-7573
• Publisher: Springer
• Peer Reviewed: Peer Reviewed
• Volume: 17
• Issue: 4
• Pages: 331-340
• DOI: https://doi.org/10.1007/s10162-016-0571-y
• Keywords: sound localization, spatial tuning, opponent process, electroencephalography, EEG, auditory system
• Public URL: http://researchrepository.napier.ac.uk/Output/2808298