ERP/ERMF-correlates of illusory and suppressed visual flashes due to sound.
Poster Presentation

Bjoern Bonath
Department of Neurology II, Otto von Guericke University, Leipziger Strasse 44, 39120 Magdeburg, Germany

*Jon Driver
Institute of Cognitive Neuroscience and Department of Psychology, University College London, 17 Queen Square, London WC1N 3AR, UK

*Ariel Schoenfeld
Department of Neurology II, Otto von Guericke University, Leipziger Strasse 44, 39120 Magdeburg, Germany

*Hans-Jochen Heinze
Department of Neurology II, Otto von Guericke University, Leipziger Strasse 44, 39120 Magdeburg, Germany

*Toemme Noesselt
Department of Neurology II, Otto von Guericke University, Leipziger Strasse 44, 39120 Magdeburg, Germany and Institute of Cognitive Neuroscience and Department of Psychology, University College London, 17 Queen Square, London WC1N 3AR, UK

     Abstract ID Number: 107
     Full text: Not available
     Last modified: March 21, 2005

Abstract
Crossmodal temporal integration of events has considerable importance in daily life. Shams et al. (2000) showed that subjects perceive an extra illusory flash when a single visual flash is presented with two auditory beeps. Here we investigated this and also whether perception of auditory events can lead to the suppression of concurrently presented visual events. Event-related potentials (ERP) and magnetic fields (ERMF) were simultaneously recorded while subjects were presented with different combinations of auditory (beeps) and visual (flashes) stimuli. Sounds and flashes occurred either congruently (3Hzvis-3Hzaud, 5Hzvis-5Hzaud) or incongruently (3Hzvis-5Hzaud, 5Hzvis-3Hzaud) at 18° eccentricity. Subjects reported the number of perceived flashes (response options: 3-5, although 4 flashes were never presented). Consistent with previous studies, a ‘positive’ illusion occurred, with reports of more than three flashes during incongruent trials with 3 flashes and 5 beeps. Importantly, subjects also reported less than five flashes during incongruent trials with 5 flashes and 3 beeps. Both illusory precepts were driven by the auditory stimulus and associated with an early index of selection towards the auditory modality in electrophysiological data. The present findings provide a neurophysiological basis for auditory-visual interactions of both enhancement and suppression.