title: Visual speech gestures modulate efferent auditory system.
abstract: Visual and auditory systems interact at both cortical and subcortical levels. Studies suggest a highly context-specific cross-modal modulation of the auditory system by the visual system. The present study builds on this work by sampling data from 17 young healthy adults to test whether visual speech stimuli evoke different responses in the auditory efferent system compared to visual non-speech stimuli. The descending cortical influences on medial olivocochlear (MOC) activity were indirectly assessed by examining the effects of contralateral suppression of transient-evoked otoacoustic emissions (TEOAEs) at 1, 2, 3 and 4 kHz under three conditions: (a) in the absence of any contralateral noise (Baseline), (b) contralateral noise + observing facial speech gestures related to productions of vowels /a/ and /u/ and (c) contralateral noise + observing facial non-speech gestures related to smiling and frowning. The results are based on 7 individuals whose data met strict recording criteria and indicated a significant difference in TEOAE suppression between observing speech gestures relative to the non-speech gestures, but only at the 1 kHz frequency. These results suggest that observing a speech gesture compared to a non-speech gesture may trigger a difference in MOC activity, possibly to enhance peripheral neural encoding. If such findings can be reproduced in future research, sensory perception models and theories positing the downstream convergence of unisensory streams of information in the cortex may need to be revised.
authors.affiliation: Oral Dynamics Lab, Department of Speech-Language Pathology, University of Toronto, 160-500 University Ave, Toronto, Canada ON M5G 1V7, Canada , Toronto Rehabilitation Institute (TRI), Toronto, Canada ON M5G 2A2, Canada.
authors.forename: Aravind Kumar
authors.initials: AK
authors.lastname: Namasivayam
authors.forename: Wing Yiu Stephanie
authors.initials: WY
authors.lastname: Wong
authors.forename: Dinaay
authors.initials: D
authors.lastname: Sharma
authors.forename: Pascal
authors.initials: P
authors.lastname: van Lieshout
mesh_terms: D000161:Acoustic Stimulation; D000293:Adolescent; D000328:Adult; D001306:Auditory Pathways / Q000502:physiology*; D001703:Biophysics; D005260:Female; D007839:Functional Laterality; D005868:Gestures; D006801:Humans; D008297:Male; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation; D013060:Speech; D055815:Young Adult
keywords: Visual speech gestures; contralateral suppression; efferent system; transient-evoked otoacoustic emissions