Affiliations: [a] Department of Neurology, University of Wisconsin, Madison, WI, USA | [b] Departments of Statistics and Biostatistics/Medical Informatics, University of Wisconsin, Madison, WI, USA | [c] Department of Psychiatry, University of Wisconsin, Madison, WI, USA
Correspondence:
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Corresponding author: Chrysanthy Ikonomidou, MD, PhD, Department of Neurology, University of Wisconsin Madison, 1685 Highland Avenue, Madison WI 53705, USA. Tel.:+1 608 2656470; Fax:+1 608 2630412; E-mail: Ikonomidou@neurology.wisc.edu.
Abstract: Background:High definition transcranial direct current stimulation (HD-tDCS) has been administered over single brain regions for small numbers of sessions. Safety, feasibility and tolerability of HD-tDCS over multiple brain regions, multiple daily stimulations and long periods are not established. Objective:We studied safety, feasibility and tolerability of daily HD-tDCS over 2-4 brain regions for 20 sessions in healthy adults. Methods:Five healthy adults underwent physical and neurological examination, electrocardiogram (EKG), electroencephalogram (EEG) and cognitive screening (ImpACT) before, during and after HD-tDCS. Four networks (left/right temporoparietal and frontal) were stimulated in sequence (20 min each) using HD-tDCS in 20 daily sessions. Sessions 1–10 included sequential stimulation of both temporoparietal networks, sessions 11–15 stimulations of 4 networks and sessions 16–20 two daily stimulation cycles of 4 networks/cycle (1.5 mA/network). Side effects, ImpACT scores and EEG power spectrum were compared before and after HD-tDCS. Results:All subjects completed the trial. Adverse events were tingling, transient redness at the stimulation site, perception of continuing stimulation after end of session and one self-resolving headache. EEG power spectrum showed decreased delta power in frontal areas several days after HD-tDCS. While at the group level ImpACT scores did not differ before and after stimulations, we found a trend for correlation between decreased EEG delta power and individual improvements in ImpACT scores after HD-tDCS. Conclusion:Prolonged, repeat daily stimulation of multiple brain regions using HD-tDCS is feasible and safe in healthy adults. Preliminary EEG results suggest that HD-tDCS may induce long lasting changes in excitability in the brain.
