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The Journal of Neuroscience, December 24, 2008, 28(52):14301-14310; doi:10.1523/JNEUROSCI.2875-08.2008

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Behavioral/Systems/Cognitive
Visual Activation and Audiovisual Interactions in the Auditory Cortex during Speech Perception: Intracranial Recordings in Humans

Julien Besle,^1,2 Catherine Fischer,^1,2,3 Aurélie Bidet-Caulet,^1,2 Francoise Lecaignard,^1,2 Olivier Bertrand,^1,2 and Marie-Hélène Giard^1,2

¹INSERM, U821, "Brain Dynamics and Cognition," 69500 Lyon, France, ²Universite Lyon 1, 69622 Lyon, France, and ³Hospices Civils de Lyon, Neurological Hospital, 69003 Lyon, France

Correspondence should be addressed to Julien Besle at the above address. Email: julien.besle{at}inserm.fr

Hemodynamic studies have shown that the auditory cortex can be activated by visual lip movements and is a site of interactions between auditory and visual speech processing. However, they provide no information about the chronology and mechanisms of these cross-modal processes. We recorded intracranial event-related potentials to auditory, visual, and bimodal speech syllables from depth electrodes implanted in the temporal lobe of 10 epileptic patients (altogether 932 contacts). We found that lip movements activate secondary auditory areas, very shortly (10 ms) after the activation of the visual motion area MT/V5. After this putatively feedforward visual activation of the auditory cortex, audiovisual interactions took place in the secondary auditory cortex, from 30 ms after sound onset and before any activity in the polymodal areas. Audiovisual interactions in the auditory cortex, as estimated in a linear model, consisted both of a total suppression of the visual response to lipreading and a decrease of the auditory responses to the speech sound in the bimodal condition compared with unimodal conditions. These findings demonstrate that audiovisual speech integration does not respect the classical hierarchy from sensory-specific to associative cortical areas, but rather engages multiple cross-modal mechanisms at the first stages of nonprimary auditory cortex activation.

Key words: auditory; visual; intracranial; speech; human; ERPs

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Received June 23, 2008; revised Sept. 25, 2008; accepted Nov. 24, 2008.

Correspondence should be addressed to Julien Besle at the above address. Email: julien.besle{at}inserm.fr

This article has been cited by other articles:

				L. H. Arnal, B. Morillon, C. A. Kell, and A.-L. Giraud Dual Neural Routing of Visual Facilitation in Speech Processing J. Neurosci., October 28, 2009; 29(43): 13445 - 13453. [Abstract] [Full Text] [PDF]

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