Abstract:
Transcranial direct current stimulation is a neuromodulatory and noninvasive brain stimulation procedure with the purpose of inducing polarity specific alteration in human brain, resulting in either increase or decrease in brain excitability. Human tDCS studies have focused on bimodal sensory integration such as audio-visual, visuo-tactile, visual-motor integration but to date, there is no study investigating the modulation of visual, auditory and tactile processing. The objective of this study is to explore whether bihemispheric brain stimulation (dual tDCS) could be effective in modulation of perception of human in the incidence of auditory, visual and tactile stimulation in a numerosity judgment task. Human brain generally processes signals from multisensory modalities at any split second and is consequently posed to two different dilemmas: which area of the brain is important in merging these signals and which of the signals are caused by an ordinary thing. Posterior Parietal Cortex is the hub of multisensory information that is the information from different modalities actually converges here. We aimed to explore the role of posterior parietal cortex (PPC) on trimodal integration and Bipolar Bihemispheric tDCS was employed for altering the brain function. For this, 25 healthy participants performed the task and were randomly allocated for the 3 groups (n=3), Sham tDCS (Stimulation 1), Active Anodal tDCS (Stimulation 2) and Active Cathodal tDCS (Stimulation 3). All participants participated in all session which consists of a baseline session and a tDCS session with a gap of one week for a total of three weeks, while receiving cathodal, anodal and sham tDCS (2mA, 20min) to bilateral posterior parietal cortices. The results reveal that down- or up- regulating the cortical excitability by tDCS can reduce or facilitate audiovisual and tactile interactions respectively i.e. right PPC is involved in the integration of trimodal sensory information and reversal of such effects was induced by left PPC.
