Transcranial Direct Current Stimulation (tDCS) is a type of neurostimulation where you apply a very small level of direct current (commonly 1mA - 2mA) through one electrode (Anode) and it flows through the brain to another electrode (Cathode). The direct current then creates a condition under the electrode that affects the neurons: the basement membrane of the neurons at the anode become more positive making them more likely to fire, and the basement membrane of the neurons at the cathode become more negative making them less likely to fire.





This has led research to experiment with different arrangements of electrodes (called montages) to encourage activity at the anode, and lower activity at the cathode; the cathode is sometimes used away from the head purely as current return and no neurophysiological activity. The amount of research using tDCS is substantial and has been growing steadily over the past ten years (see graph below).





A few months ago, I did a short review of the main topics of tDCS research:

Hits on Pubmed



tDCS and Learning 322

tDCS and Stroke 288

tDCS and Memory 214

tDCS and Depression 208

tDCS and Pain 162

tDCS and Safety 108

tDCS and Cognitive Enhancement 55

tDCS and Bipolar 31

tDCS and Parkinson's 25

tDCS and Alzheimer's 13

Considering the clinical uses of tDCS, not surprisingly it is limited to neurological disorders. As you can imagine with the type of growth seen in the graph of the number of tdcs studies published by year, that topics of tdcs research is growing wider and deeper. That is there are more conditions that are investigated, and with a few conditions, more studies are made. The top clinical conditions used for tDCS are depression, stroke, and pain.The use of tDCS in the clinical environment is still in its infancy. Mostly not used in general practice, tDCS is still the realm of Brain Stimulation Centers throughout the US; practices that specialize in brain stimulation techniques. Hopefully this changes over the next few years, as tDCS devices are so easy to acquire, tDCS techniques are so easy to implement, and the side effects are minimal, the technology is ready for growth. Because of lack of clinical precedent, it is key to look into the research to understand protocols.Below I will highlight a little of the research and give the summary for general interest.1. Boggio PS, Rigonatti SP, Ribeiro RB, Myczkowski MI, Nitsche MA, et al. A randomized, double-blind clinical trial on the efficacy of cortical direct current stimulation for the treatment of major depression. Intl J of Neuropsychopharma 2008;11:249-254."The results of this study show that cortical stimulationwith tDCS is associated with a significant reduction indepression scores that is specific to the site of stimulationand lasts for at least 30 d after the end of treatment.": Anode L DorsoLateral PreFrontal Cortex (DLPFC), and Cathode R Supraorbital2mA20min per day for 10 days2. Loo CK, Alonzo A, Martin D, Mitchell PB, Galvez V, et al. Transcranial direct current stimulation for depression: 3 week randomized, sham controlled trial. British J of Psychiatry 2012;200:52-59."Although results after 3 weeks of daily tDCS were modest, thenumber of responders after 6 weeks of treatment was much moreencouraging, and comparable with outcomes from a recent largestudy of 6 weeks of TMS given on an open-label basis toparticipants with pharmacotherapy-resistant depression.The response rate was superior to that reportedfor antidepressant medication in individuals who had failed a firstcourse of medication in the large Sequenced TreatmentAlternatives to Relieve Depression (STAR*D) study.This suggests that tDCS has meaningful antidepressant efficacy,including in those individuals resistant to pharmacotherapy.": Anode L DorsoLateral PreFrontal Cortex (DLPFC), and Cathode R Lateral Orbit (F8)2mAEvery day for three weeks then once per week for three more weeks.3. Martin DM, Alonzo A, Ho Ka, Player MK, Mitchell PB, et al. Continuation of transcranial direct current stimulation for the prevention of relapse in major depression. J Affective Disorders 2012;144:274-278."Continuation tDCS,given weekly for the first 3 months,resulted in the majority of responders remaining well, thoughthe relapse rate increased after treatments were spaced to fort-nightly in the subsequent 3 months.In the absence of a controlgroup of responders who did not go on to receive continuationtDCS treatments,we cannot conclude that the continuationtreatments were beneficial in preventing relapse,though thehigher rate of relapse when treatments were spaced to fortnightlysuggests that the weekly treatment schedule may be a usefultreatment strategy.": Anode L DorsoLateral PreFrontal Cortex (DLPFC), and some with Cathode R Lateral Orbit (F8) and some with Cathode R upper shoulder2mAWeekly for the first three months then every other week for three months after that.Even though all three studies listed above have Anode L DLPFC, this is most definitely not the only montage used for depression and tDCS; but it is a well known choice.I want to follow up with a later blog for research highlight of tDCS use for Stroke and Pain.