Abstract

Transcranial direct current stimulation (tDCS) is a non-invasive stimulation method that has been shown to modulate the excitability of the motor and visual cortices in human subjects in a polarity dependent manner in previous studies. The aim of our study was to investigate whether anodal and cathodal tDCS can also be used to modulate the excitability of the human primary somatosensory cortex (S1). We measured paired-pulse suppression (PPS) of somatosensory evoked potentials in 36 right-handed volunteers before and after anodal, cathodal, or sham stimulation over the right non-dominant S1. Paired-pulse stimulation of the median nerve was performed at the dominant and non-dominant hand. After anodal tDCS, PPS was reduced in the ipsilateral S1 compared to sham stimulation, indicating an excitatory effect of anodal tDCS. In contrast, PPS in the stimulated left hemisphere was increased after cathodal tDCS, indicating an inhibitory effect of cathodal tDCS. Sham stimulation induced no pre–post differences. Thus, tDCS can be used to modulate the excitability of S1 in polarity-dependent manner, which can be assessed by PPS. An interesting topic for further studies could be the investigation of direct correlations between sensory changes and excitability changes induced by tDCS.

Highlights

  • Cortical excitability is regarded as an essential factor contributing to successful perceptual learning

  • The aim of our study was to use paired-pulse stimulation in combination with somatosensory evoked potentials (SEPs) recordings as a well-established marker of somatosensory cortical excitability (Höffken et al, 2007, 2010, 2013; Lenz et al, 2011, 2012) to investigate whether anodal and cathodal Transcranial direct current stimulation (tDCS) modulate the excitability of the human somatosensory cortex in the same polarity dependent manner as it was previously described for the motor and visual cortices

  • The present study investigated whether anodal and cathodal tDCS modulate the excitability of the human primary somatosensory cortex in the same polarity dependent manner as it was previously described for the motor and visual cortices

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Summary

Introduction

Cortical excitability is regarded as an essential factor contributing to successful perceptual learning. Transcranial direct current stimulation (tDCS) is a non-invasive stimulation method which has been shown in previous studies to modulate the excitability of the motor and visual cortices in human subjects in a polarity dependent manner (Nitsche and Paulus, 2000, 2001; Antal et al, 2003, 2006; Nitsche et al, 2003a, 2008; Moliadze et al, 2014). In the second study (Dieckhöfer et al, 2006) there was a significant reduction of the N20 source amplitude after cathodal tDCS to the somatosensory cortex These studies support the hypothesis that tDCS can induce excitability changes in S1 in a polarity dependent manner

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