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Speech processing: from peripheral to hemispheric asymmetry of the auditory system
Diane S Lazard1, Jean-Louis Collette, Xavier Perrot
1Ecole Normale Supérieure, Inserm U960, Paris, France. dianelazard@yahoo.fr
The Laryngoscope
|November 19, 2011
Summary
Speech processing shows left-hemispheric dominance for complex sounds, explained by two theories on temporal and spectral resolution. Auditory aging highlights clinical implications of this brain asymmetry.
Area of Science:
- Neuroscience
- Auditory Processing
- Speech Perception
Background:
- Auditory pathways exhibit side-dependent specificities, with a notable left hemispheric dominance in language processing.
- Understanding hemispheric asymmetry in speech is crucial for comprehending brain function and potential disorders.
Purpose of the Study:
- To provide a didactic review of two complementary theories explaining hemispheric asymmetry in speech processing for non-specialists.
- To explore the neurophysiological and behavioral evidence supporting speech processing lateralization.
Main Methods:
- Review of anatomico-physiological and clinical observations of auditory asymmetry and interhemispheric connections.
- Analysis of behavioral experiments, including the dichotic listening paradigm.
- Examination of functional neuroimaging studies (fMRI, PET) investigating speech processing specialization.
Main Results:
- Speech processing is bilateral at early phonological levels but shows left-hemispheric dominance for higher-level processing.
- Two theories, asymmetric sampling in time and spectral/temporal resolution trade-off, propose mechanisms for this asymmetry.
- These theories suggest that acoustic signal tuning principles influence speech processing organization.
Conclusions:
- Hemispheric asymmetry in speech processing is influenced by distinct temporal integration windows in each hemisphere.
- While theories offer explanations, the precise mechanisms and origins of speech processing asymmetry remain under investigation.
- Alterations in hemispheric asymmetry, as seen in auditory aging, have significant clinical implications.
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