Abstract
Introduction. tRNS has been used to modulate cortical excitability and facilitate behavior, particularly using perceptual learning tasks. Typically, these studies analyze the facilitatory effects on a single task, and its transfer to untrained tasks. Yet, there is a lack of studies that investigate the impact of tRNS during cross-task training. In these experiments we explored the effect of dual-task training using identical visual stimuli across two different attentional tasks. We used tRNS to modulate learning to identify the cortical site directly involved in cross-task training. Methods. Subjects participated in a 6-days experiment (1 session/day). During each session, subjects were simultaneously trained on two tasks: a temporal order judgment (TOJ) and an orientation discrimination (OD), using two Gabors presented to the left and right of fixation. Each subject was trained at their individual TOJ and OD psychophysical thresholds, across two levels: easy and hard trials. At the beginning of each trial, subjects were instructed which of the two tasks to perform. These two tasks were randomly intermixed within each block. Subjects were assigned to one of three conditions in a between-subject design: tRNS over hMT+, tRNS over parietal cortex and sham stimulation. Active tRNS or sham were delivered for 25 minutes concurrent with the task, during days 2-4 (training phase). We expected tRNS over parietal to selectively impact and enhance training. Results. Participants' performance significantly improved in both tasks (TOJ and OD) after tRNS over parietal compared to hMT+ and sham. Crucially this improvement was selective for difficult trials only for both tasks. Conclusions. These findings demonstrate the direct involvement of the parietal cortex in perceptual learning, while subjects are simultaneously training on two cognitive tasks that are visually identical but require different attentional processes (temporal and spatial).
Meeting abstract presented at VSS 2017