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

Clin Neurophysiol. 2007 May;118(5):1166-70. doi: 10.1016/j.clinph.2007.01.010. Epub 2007 Feb 27.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Dose-Response Relationship, Drug
  • Electric Stimulation / adverse effects
  • Electric Stimulation / methods*
  • Electrodes* / adverse effects
  • Female
  • Humans
  • Male
  • Middle Aged
  • Pruritus / chemically induced
  • Sodium Chloride / pharmacology*


  • Sodium Chloride