Daily transcranial direct current stimulation (tDCS) leads to greater increases in cortical excitability than second daily transcranial direct current stimulation.
BACKGROUND
Evidence from recent clinical trials suggests that transcranial direct current stimulation (tDCS) may have potential in treating neuropsychiatric disorders. However, the optimal frequency at which tDCS sessions should be administered is unknown.


OBJECTIVE
This study investigated the effects of daily or second daily tDCS sessions on motor cortical excitability, over a 5-day period.


METHODS
Twelve healthy volunteers received daily or second daily sessions of tDCS to the left primary motor cortex over the study period, in a randomized, intraindividual crossover design. Motor cortical excitability was assessed before and after tDCS at each session through responses to transcranial magnetic stimulation.


RESULTS
Over a fixed 5-day period, tDCS induced greater increases in MEP amplitude when given daily rather than second daily. Analyses showed that this difference reflected greater cumulative effects between sessions rather than a greater response to each individual tDCS session.


CONCLUSIONS
These results demonstrate that in the motor cortex of healthy volunteers, tDCS alters cortical excitability more effectively when given daily rather than second daily over a 5-day period.
School of Psychiatry, University of New South Wales, Black Dog Institute, Sydney, Australia.
Angelo
A
Alonzo
School of Psychiatry, University of New South Wales, Black Dog Institute, Sydney, Australia.
Joseph
J
Brassil
Neuroscience Research Australia, Sydney; School of Medical Sciences, University of New South Wales, Sydney, Australia.
Janet L
JL
Taylor
School of Psychiatry, University of New South Wales, Black Dog Institute, Sydney, Australia.
Donel
D
Martin
School of Psychiatry, University of New South Wales, Black Dog Institute, Sydney, Australia; St. George Hospital, Sydney, Australia. Electronic address: colleen.loo@unsw.edu.au.
Colleen K
CK
Loo
D000328:Adult; D004307:Dose-Response Relationship, Radiation; D019054:Evoked Potentials, Motor / Q000502:physiology* / Q000528:radiation effects*; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology* / Q000528:radiation effects*; D011829:Radiation Dosage; D050781:Transcranial Magnetic Stimulation / Q000379:methods*; D055815:Young Adult