Random Noise Stimulation Improves Neuroplasticity in Perceptual Learning

Abstract

Perceptual learning is considered a manifestation of neural plasticity in the human brain. We investigated brain plasticity mechanisms in a learning task using noninvasive transcranial electrical stimulation (tES). We hypothesized that different types of tES would have varying actions on the nervous system, which would result in different efficacies of neural plasticity modulation. Thus, the principal goal of the present study was to verify the possibility of inducing differential plasticity effects using two tES approaches [i.e., direct current stimulation (tDCS) and random noise stimulation (tRNS)] during the execution of a visual perceptual learning task.One hundred seven healthy volunteers participated in the experiment. 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 stimulation were applied to the visual areas of the brain in a group of volunteers while they performed an orientation discrimination task. 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. We concluded that the mechanism of action of tRNS was based on repeated subthreshold stimulations, which 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.

The application of online transcranial random noise stimulation and perceptual learning in the improvement of visual functions in mild myopia

“…In fact, by using the same PL paradigm (contrast detection) in myopic participants, in a previous study we found that 24 sessions were needed to achieve a VA improvement of 0.16 LogMAR, whereas no improvement in CS was found even with such a long training (Camilleri, Pavan, Ghin, Battaglini, et al, 2014). However, if PL is boosted by the concomitant administration of hf-tRNS as shown by previous studies (Camilleri, Pavan, Ghin, Battaglini, et al, 2014;Campana, et al, 2014;Fertonani, et al, 2011;Pirulli, et al, 2013), then 8 sessions of training become enough efficacious to improve uncorrected VA of a similar amount of 24 training sessions with no concurrent stimulation, and to significantly improve uncorrected CS (whereas no improvement was obtained with 24 training sessions using the same paradigm (Camilleri, Pavan, Ghin, Battaglini, et al, 2014).…”

“…The frequencies ranged from 100 to 640Hz (high frequency range). This stimulation protocol has been demonstrated efficacious in boosting perceptual learning in previous studies (Camilleri, Pavan, Ghin, Battaglini, et al, 2014;Fertonani, et al, 2011;Pirulli, et al, 2013). The active electrode had an area of 16 cm 2 and was placed over the occipital cortex measured at ~3 cm above the inion.…”

“…Participants in group 1 (PL+tRNS) were administered hf-tRNS (1.5mA) during the first 25 minutes of each session, which covered the first 5 blocks (Fertonani, et al, 2011).…”

“…Unlike tDCS, tRNS has only recently been explored within the visual domain (Camilleri, Pavan, Ghin, Battaglini, et al, 2014;Campana, et al, 2014;Fertonani, Pirulli, & Miniussi, 2011;Pirulli, Fertonani, & Miniussi, 2013). Fertonani and colleagues conducted a study testing the efficacy of different stimulation protocols on an orientation discrimination task (Fertonani, et al, 2011).…”

“…Fertonani and colleagues conducted a study testing the efficacy of different stimulation protocols on an orientation discrimination task (Fertonani, et al, 2011). Their results concluded that high frequency tRNS (hf-tRNS), that is tRNS with a frequency ranging from 100 to 640 Hz, was the most efficacious type of NIBS for boosting PL in healthy participants, when compared with low frequency random noise, direct current (anodal and cathodal) and sham stimulation.…”