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BIOLOGICAL SCIENCES / NEUROSCIENCE
Simulation of talking faces in the human brain improves auditory speech recognition
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*Wellcome Trust Centre for Neuroimaging, University College London, Queen Square, London WC1N 3BG, United Kingdom; Medical School, University of Newcastle, Framlington Place, Newcastle-upon-Tyne NE2 4HH, United Kingdom; Department of Neurology, J. W. Goethe University, Schleusenweg, 60528 Frankfurt am Main, Germany; ¶Department of Psychological Basic Research, University of Vienna, Liebiggasse, 1010 Vienna, Austria; ||Departement d'Etudes Cognitives, École Normale Supérieure, 75005 Paris, France; **CEA, NeuroSpin, 91401 Gif-sur-Yvette, France; and Institut National de la Santé et de la Recherche Médicale, U562, 91401 Gif-sur-Yvette, France
Edited by Dale Purves, Duke University Medical Center, Durham, NC, and approved March 15, 2008 (received for review November 15, 2007)
Human face-to-face communication is essentially audiovisual. Typically, people talk to us face-to-face, providing concurrent auditory and visual input. Understanding someone is easier when there is visual input, because visual cues like mouth and tongue movements provide complementary information about speech content. Here, we hypothesized that, even in the absence of visual input, the brain optimizes both auditory-only speech and speaker recognition by harvesting speaker-specific predictions and constraints from distinct visual face-processing areas. To test this hypothesis, we performed behavioral and neuroimaging experiments in two groups: subjects with a face recognition deficit (prosopagnosia) and matched controls. The results show that observing a specific person talking for 2 min improves subsequent auditory-only speech and speaker recognition for this person. In both prosopagnosics and controls, behavioral improvement in auditory-only speech recognition was based on an area typically involved in face-movement processing. Improvement in speaker recognition was only present in controls and was based on an area involved in face-identity processing. These findings challenge current unisensory models of speech processing, because they show that, in auditory-only speech, the brain exploits previously encoded audiovisual correlations to optimize communication. We suggest that this optimization is based on speaker-specific audiovisual internal models, which are used to simulate a talking face.
fMRI | multisensory | predictive coding | prosopagnosia
Author contributions: K.v.K. designed research; K.v.K., Ö.D., M.G., A.-L.G., C.A.K., T.G., and A.K. performed research; S.J.K. contributed new reagents/analytic tools; K.v.K. and Ö.D. analyzed data; and K.v.K. and S.J.K. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/cgi/content/full/0710826105/DCSupplemental.
To whom correspondence should be addressed. E-mail: kkriegs{at}fil.ion.ucl.ac.uk
© 2008 by The National Academy of Sciences of the USA
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