Perception of comfort during transcranial DC stimulation: effect of NaCl solution concentration applied to sponge electrodes.

Overview

OBJECTIVE: To investigate the relationship between perception of comfort and electrolyte concentration and applied voltage during transcranial direct current stimulation (tDCS). METHODS: NaCl solutions (15, 140 and 220 mM NaCl) or deionised water were used as electrolytes to dampen tDCS sponge electrodes. Subjects (14, 7 M, 20-60 years of age) rated comfort on an 11-point scale during 2 min of tDCS (1 mA). RESULTS: Overall participants rated tDCS as comfortable. Perception of comfort was negatively correlated with NaCl concentration (Spearman's rho=-0.88; p<0.05), and a logarithmic relationship was found between applied voltage and ionic strength of electrolytes (Pearson's r=-0.635; p<0.01). There was no relationship between applied voltage and perception of comfort. CONCLUSIONS: The application of NaCl solutions between 15 and 140 mM to sponge electrodes is more likely to be perceived as comfortable during tDCS. SIGNIFICANCE: The reporting of solution concentration and ratings of perception would be useful adjuncts to tDCS studies.

Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology Journal