[Equipe Audition] [CNRS] [LPP Paris 5] [ENS] [DEC]

Séminaires Audition 2007 : David McAlpine

Le jeudi 22 mars 2007, de 10h à 11h, à l'ENS, 45 rue d'Ulm, salle des Actes.

Pr David McAlpine, directeur du Ear Institute, University College London.

The representation of auditory space in the human brain.

Humans make use of small differences in the timing of a sound at the two ears to determine the location of the sound source. For 60 years the major model developed to understand how the brain encodes these interaural time differences (ITDs) has consisted of an array of coincidence detectors innervated by series of delay lines. The purpose of this arrangement is to translate information about the timing of a sound at each ear into a place code - a position within an array of neurons tuned to a specific ITD and, by extension, a position in auditory space. Here, I present neurophysiological evidence from the mammalian brain indicating that this model can no longer hold. Using in vivo electrophysiology in small mammals, functional MRI scanning in the human midbrain and recordings of the mismatch negativity potential, I show that the brain's representation of ITD is in the form of a distributed code, with no strict relationship between the side on which a sound is perceived and the brain hemisphere activated. Depending on the magnitude of the ITD, either the ipsilateral or contralateral midbrain and cortex may be more active. These data indicate the need for a new model of spatial hearing.

Ecole Normale Supérieure, 45 rue d'Ulm, 75005 Paris [plan]

[Equipe Audition] [CNRS] [LPP Paris 5] [ENS] [DEC]