Folmli, Brookes, Turman, Bulent, Johnson, Peter, and Abbott, Allan (2018) Dose-response of somatosensory cortex repeated anodal transcranial direct current stimulation on vibrotactile detection. A randomized sham controlled trial. Journal of Neurophysiology, 120 (2). pp. 610-616.

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Abstract

This randomized sham-controlled trial investigated anodal transcranial direct current stimulation (tDCS) over the somatosensory cortex contralateral to hand dominance for dose-response (1 mA, 20 min × 5 days) effects on vibrotactile detection thresholds (VDT). VDT was measured before and after tDCS on days 1, 3, and 5 for low- (30 Hz) and high-frequency (200 Hz) vibrations on the dominant and nondominant hands in 29 healthy adults (mean age = 22.86 yr; 15 men, 14 women). Only the dominant-hand 200-Hz VDT displayed statistically significant medium effect size improvement for mixed-model analysis of variance time-by-group interaction for active tDCS compared with sham. Post hoc contrasts were statistically significant for dominant-hand 200-Hz VDT on day 5 after tDCS compared with day 1 before tDCS, day 1 after tDCS, and day 3 before tDCS. There was a linear dose-response improvement with dominant-hand 200-Hz VDT mean difference decreasing from day 1 before tDCS peaking at −15.5% (SD = 34.9%) on day 5 after tDCS. Both groups showed learning effect trends over time for all VDT test conditions, but only the nondominant-hand 30-Hz VDT was statistically significant (P = 0.03), although post hoc contrasts were nonsignificant after Šidák adjustment. No adverse effects for tDCS were reported. In conclusion, anodal tDCS at 1 mA, 20 min × 5 days on the dominant sensory cortex can modulate a linear improvement of dominant-hand high-frequency VDT but not low-frequency or nondominant-hand VDT.

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