P 21. Temporal cortex transcranial direct current stimulation modulates the performance in an audio-visual integration task

Introduction Organisms are able to combine information from different sensory channels. This enables them to obtain a coherent representation of the environment by a process termed multisensory integration. The interaction of different sensory inputs minimizes perceptual uncertainty in localizing and detecting objects in the observers surrounding ( MacLeod and Summerfield, 1990 ). Thus, the integration of information arising from the auditory and visual domain is a crucial cognitive function for the perception of objects in a certain distance ( Welch and Warren, 1986 ). Objectives While audio-visual integration has been studied in the past showing multimodal and unimodal areas involved in this dual process, the influence of transcranial direct current stimulation (tDCS) on these cortical regions has been poorly explored. The aim of the present study was to investigate the behavioral and electrophysiological effects of tDCS applied over the left temporal cortex during an audio-visual integration task and in parallel to determine electrophysiological correlates of multisensory integration by means of electroencephalography (EEG). Materials and methods 10 healthy subjects received in a randomized order at three consecutive days anodal, cathodal or sham tDCS (referenced over the right supraorbital area) over the left temporal cortex for 30 min with a current strength of 2 mA. Subsequently, an audio-visual task ( Noesselt et al., 2010 ) and simultaneous EEG recording started. Participants had to detect Gabor Patches which were presented either solely or with a tone (cf. Fig. 1 ). These Gabor Patches differ in contrast sensitivity (high or low salience). Results Results show that tDCS over the left temporal cortex modulates behavioral performance in a multisensory integration task. In parallel, we found tDCS-induced modulations of event-related potential components demonstrating that tDCS can interact with the process of multisensory audio-visual integration. Conclusion This study demonstrates tDCS-induced changes in multisensory processing. Modulating the reactivity of the auditory cortex by means of tDCS resulted in a modified performance and related electrophysiological responses in an audio-visual integration task.