This work was supported by grants from l'Association des Anciens Internes des Hôpitaux de Paris (http://www.aaihp.fr). The sponsor did not participate in either the writing of this article or in the decision to submit it. The authors alone are responsible for the content and writing of this article. The authors have no other funding, financial relationships, or conflicts of interest to disclose.
Speech processing: From peripheral to hemispheric asymmetry of the auditory system†
Article first published online: 17 NOV 2011
Copyright © 2011 The American Laryngological, Rhinological, and Otological Society, Inc.
Volume 122, Issue 1, pages 167–173, January 2012
How to Cite
Lazard, D. S., Collette, J.-L. and Perrot, X. (2012), Speech processing: From peripheral to hemispheric asymmetry of the auditory system. The Laryngoscope, 122: 167–173. doi: 10.1002/lary.22370
- Issue published online: 19 DEC 2011
- Article first published online: 17 NOV 2011
- Manuscript Accepted: 1 SEP 2011
- Manuscript Revised: 26 JUN 2011
- Manuscript Received: 8 FEB 2011
- Temporal integration windows, spectro-temporal resolution, dichotic listening, functional imaging, medial olivocochlear efferent system, corpus callosum, presbycusis
Language processing from the cochlea to auditory association cortices shows side-dependent specificities with an apparent left hemispheric dominance. The aim of this article was to propose to nonspeech specialists a didactic review of two complementary theories about hemispheric asymmetry in speech processing. Starting from anatomico-physiological and clinical observations of auditory asymmetry and interhemispheric connections, this review then exposes behavioral (dichotic listening paradigm) as well as functional (functional magnetic resonance imaging and positron emission tomography) experiments that assessed hemispheric specialization for speech processing. Even though speech at an early phonological level is regarded as being processed bilaterally, a left-hemispheric dominance exists for higher-level processing. This asymmetry may arise from a segregation of the speech signal, broken apart within nonprimary auditory areas in two distinct temporal integration windows—a fast one on the left and a slower one on the right—modeled through the asymmetric sampling in time theory or a spectro-temporal trade-off, with a higher temporal resolution in the left hemisphere and a higher spectral resolution in the right hemisphere, modeled through the spectral/temporal resolution trade-off theory. Both theories deal with the concept that lower-order tuning principles for acoustic signal might drive higher-order organization for speech processing. However, the precise nature, mechanisms, and origin of speech processing asymmetry are still being debated. Finally, an example of hemispheric asymmetry alteration, which has direct clinical implications, is given through the case of auditory aging that mixes peripheral disorder and modifications of central processing.