Cerebral Cortex Advance Access published online on January 31, 2007
Cerebral Cortex, doi:10.1093/cercor/bhl178
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Binding Symbols and Sounds: Evidence from Event-Related Oscillatory Gamma-Band Activity
1 Institute of Psychology I, University of Leipzig, Seeburgstraße 14-20, D-04103 Leipzig, Germany, 2 Helsinki Collegium for Advanced Studies, University of Helsinki, Finland, 3 Cognitive Brain Research Unit, Department of Psychology, University of Helsinki, Finland, 4 Helsinki Brain Research Center, Helsinki, Finland
Address correspondence to Andreas Widmann. Email: widmann{at}uni-leipzig.de.
The present study intended to examine the neural basis of audiovisual integration, hypothetically achieved by synchronized gamma-band oscillations (30–80 Hz) that have been suggested to integrate stimulus features and top–down information. To that end, we studied the impact of visual symbolic information on early auditory sensory processing of upcoming sounds. In particular, we used a symbol-to-sound–matching paradigm in which simple score-like patterns predict corresponding sound patterns. Occasionally, a single sound is incongruent with the corresponding element of the visual pattern. In response to expected sounds congruent with the corresponding visual symbol, a power increase of phase-locked (evoked) activity in the 40-Hz band was observed peaking 42-ms poststimulus onset. Thus, for the first time, we demonstrated that the comparison process between a neural model, the expectation, and the current sensory input is implemented at very early levels of auditory processing. Subsequently, expected congruent sounds elicited a broadband power increase of non–phase-locked (induced) activity peaking 152-ms poststimulus onset, which might reflect the formation of a unitary event representation including both visual and auditory aspects of the stimulation. Gamma-band responses were not present for unexpected incongruent sounds. A model explaining the anticipatory activation of cortical auditory representations and the match of experience against expectation is presented.
Key Words: audiovisual integration • audition • event-related brain potentials • gamma-band oscillatory activity • neural model • vision
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