Abstract
In the present study we tested the effects of different transcranial direct current stimulation (tDCS) protocols in the formation of visuo-spatial contextual learning (VSCL). The study comprised three experiments designed to evaluate tDCS-induced changes in VSCL measures collected during the execution of a visual search task widely used to examine statistical learning in the visuo-spatial domain. In Experiment 1, we probed for the effects of left-posterior parietal cortex (PPC) anodal-tDCS (AtDCS) at different timings (i.e. offline and online) and intensities (i.e. 3 mA and 1.5 mA). The protocol producing the more robust effect in Experiment 1 was used in Experiment 2 over the right-PPC, while in Experiment 3, cathodal-tDCS (CtDCS) was applied over the left-PPC only at a high intensity (i.e. 3 mA) but varying timing of application (offline and online). Results revealed that high intensity offline AtDCS reduced VSCL regardless of the stimulation side (Experiment 1 and 2), while no significant behavioral changes were produced by both online AtDCS protocols (Experiment 1) and offline/online CtDCS (Experiment 3). The reduced VSCL could result from homeostatic regulatory mechanisms hindering normal task-related neuroplastic phenomena.
Highlights
In the present study we tested the effects of different transcranial direct current stimulation protocols in the formation of visuo-spatial contextual learning (VSCL)
We developed three separate experiments in order to test the effects produced by different transcranial direct current stimulation (tDCS) protocols on visuo-spatial contextual learning (VSCL)
No other main effect or interactions were significant to the statistical analysis. (EX)In order to control whether differences in VSCL scores could be attributable to between groups differences in general task performance, two 5 × 13 mixed analyses of variance (ANOVA) with the between factor Stimulation (5 levels) and the within factor Blocks (13 levels) were performed on accuracy scores and RTs to new trials
Summary
In the present study we tested the effects of different transcranial direct current stimulation (tDCS) protocols in the formation of visuo-spatial contextual learning (VSCL). What is less documented is whether similar regulatory mechanisms are retrievable outside the motor cortex and/ or primary sensory areas It is not clear whether the abovementioned interactions between tES- and task-related brain activity occur when the learning paradigm involves a more distributed network of cortical activity. In Experiment 1, left-posterior parietal cortex (PPC) AtDCS (i.e., target electrode on left PPC and return electrode on right arm) applied at different timings (offline/online) and intensities (3 mA and 1.5 mA) was associated with the execution of a VSCL task widely used in previous studies examining statistical learning in the visuo-spatial domain[25]. We expected offline CtDCS to produce facilitatory effects on VSCL, while online CtDCS to significantly interfere with VSCL
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