Perceptual learning can be improved by transcranial random noise stimulation

Perceptual learning is considered a manifestation of neural plasticity in the human brain. We investigated brain plasticity mechanisms in a visual perceptual learning task using non-invasive transcranial electrical stimulation (tES, i.e., direct current stimulation tDCS and random noise stimulation tRNS) applied on the visual areas. Our hypothesis is that different types of tES would have varying actions on the nervous system, which would result in different efficacies of neural plasticity modulation. 107 healthy volunteers participated in the experiment, assigned to the groups: high-frequency tRNS (hf-tRNS, 100-640 Hz), low-frequency tRNS (lf-tRNS, 0.1-100 Hz), anodal-tDCS (a-tDCS), cathodal-tDCS (c-tDCS) and sham. Furthermore, a control group was stimulated on the vertex (Cz). The analysis showed a learning effect during task execution that was differentially modulated according to the stimulation conditions. Post-hoc comparisons revealed that hf-tRNS significantly improved performance accuracy compared with a-tDCS, c-tDCS, sham and Cz stimulations. Our results confirmed the efficacy of hf-tRNS over the visual cortex in improving behavioral performance and showed its superiority in comparison to others tES. The repeated subthreshold stimulation of tRNS may prevent homeostasis of the system and potentiate task-related neural activity. This result highlights the potential of tRNS and advances our knowledge on neuroplasticity induction approaches.