P 145. Modulating multimodal feature integration with transcranial direct current stimulation (tDCS) over the parietal and prefrontal cortices

Abstract

Understanding how the brain integrates features from diverse sensory modalities that are processed in distinct cortical regions calls for the examination of integration processes (the binding problem). Recent studies of feature-repetition effects demonstrated interactions across perceptual features from different modalities: repeating only some features of the multimodal stimuli hinders performance compared to repeating all or none of the features. These partial-repetition costs point to the existence of temporary memory traces of multimodal information (object file/ event files). Here, we investigated whether brain stimulation with transcranial direct current stimulation (tDCS) influences the integration processes. In Experiment 1, tDCS was employed over the left dorsolateral prefrontal cortex (DLPFC) which is linked with cognitive control processes, while in Experiment 2, we applied tDCS over the right posterior parietal cortex (PPC) which is a multimodal region associated with sensory convergence of multisensory information. In different sessions, healthy participants received anodal, cathodal, or sham tDCS (2 mA, 15 min) while performing the audio-visual event file task. The results show that there is no significant difference in terms of partial repetition costs between the stimulations over the left DLPFC, yet anodal stimulation over the right PPC eliminated the integration between auditory and visual features, as compared to cathodal and sham stimulation. In additional control experiments no such effect was found in the left PPC. These findings emphasize the role of the right posterior parietal cortex in multimodal feature integration. tDCS may be considered as an effective therapeutic modulation tool in cognitive rehabilitation, especially in populations where multimodal integration does not operate in the most resourceful manner, such as in older adults and in autistic children.