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Megan A.K. Peters, Benjamin Thompson, Lotfi B. Merabet, Allan D. Wu, Ladan Shams; Anodal tDCS to V1 blocks visual perceptual learning consolidation. Journal of Vision 2013;13(9):602. doi: 10.1167/13.9.602.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose and background. The purpose of this study was to examine the effects of visual cortex Transcranial Direct Current Stimulation (tDCS) on contrast sensitivity and consolidation of learning. Previous studies have demonstrated improvements in visual contrast sensitivity as a result of anodal tDCS, and decrements in sensitivity due to cathodal tDCS. Further, other studies have demonstrated polarity-specific effects of tDCS to motor cortices on consolidation of learned motor tasks. However, no studies have examined effects of tDCS on overnight consolidation of visual perceptual learning.
Methods. Over two consecutive days, twenty-four healthy participants performed a contrast detection task. Each day included two sessions: a baseline measurement followed by measurements made during tDCS stimulation (active or sham). Participants were separated into three groups of eight participants each. One group received anodal stimulation to primary visual cortex (V1) on the first day, while another received cathodal stimulation; stimulation polarity was reversed for these groups on the second day. The third group received sham stimulation on both days.
Results. We observed no improvements or decrements in contrast sensitivity relative to the same-day baseline during real tDCS, nor were there any measurable within-session learning trends. However, participants in the groups that received either cathodal or sham tDCS on Day 1 demonstrated significantly improved task performance on Day 2, while no such improvement was found for the participants who received anodal stimulation on Day 1.
Discussion and conclusions. These results indicate that anodal tDCS blocked overnight consolidation of visual learning; possible mechanisms for this blocking include engagement of inhibitory homeostatic plasticity mechanisms, or alteration of the signal-to-noise ratio within stimulated cortex. To our knowledge this is the first study to demonstrate the effects of tDCS on consolidation of learning within the visual cortex.
Meeting abstract presented at VSS 2013
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