Investigating the role of different brain areas in temporal processing using non-invasive brain stimulation techniques

The understanding of the mechanisms underlying the temporal representation of duration in milliseconds/seconds range remains a complex issue. Different brain areas have been identified as critical in temporal processing depending on temporal range and modalities used. We will used non-invasive techniques (tDCS and tRNS) applied over the primary auditory (A1) and visual (V1) cortices as well as parietal cortex to investigate the specific role of these areas in temporal processing in the milliseconds range. Study 1 involved 48 participants; 24 participants were stimulated over A1 and 24 participants were stimulated over V1. Participants performed time bisection tasks, in the visual and the auditory modalities, involving standard durations lasting 300 ms (short) and 900 ms (long). When tDCS was delivered over A1, results showed higher temporal variability under anodic stimulation compared to sham and higher variability in the visual compared to the auditory modality. When tDCS was delivered over V1 higher variability was observed in the visual compared to the auditory modality. Study 2 included 48 participants all stimulated over right parietal cortex. Participants were divided into 4 groups depending on the modality of the markers that we used to define the temporal intervals (visual-visual; visual-auditory; auditory-visual and auditory-auditory). Higher variability was also observed when tRNS was applied over the parietal cortex but only when the temporal intervals where marker by both auditory and visual modality. Our results suggest a modality independent role of A1 and a modality specific role of V1 in the processing of temporal intervals in the visual modality. Moreover, we confirmed the role of parietal cortex in processing time when multi-modalities are used.