Practice in Clinical & Health Psychology
What is tDCS?
Transcranial Direct-Current Stimulation

 

 

A non-invasive and safe neurostimulation therapy for the treatment of depression, obessive-compulsive disorder, migraine, and chronic pain.

 

 

Transcranial Direct Current Stimulation (tDCS):
A new neurostimulation therapy

Transcranial direct current stimulation (tDCS) is a new form of neurostimulation that may be used to safely treat a variety of clinical conditions including depression, obsessive-compulsive disorder, migraine, and central and neuropathic chronic pain. TDCS can also relieve the symptoms of narcotic withdrawal and reduce cravings for drugs, including nicotine and alcohol. There is some limited evidence that tDCS can be used to increase frontal lobe functioning and reduce impulsivity and distractibility in persons with attention deficit disorder. TDCS has also been shown to boost verbal and motor skills and improve learning and memory  in healthy people.

TDCS involves the injection of a weak (very low amperage) non-alternating electrical current to the head through surface electrodes to generate an electromagnetic field that selectively modulates the activity of neurons in the cerebral cortex of the brain.

Illustration of transcranial DC stimulation device.

The exact mechanism of tDCS is not clear but extensive neurophysiological research has shown that direct current (DC) electricity penetrates the skull and outer layers of the cortex to modify neuronal cross-membrane resting potentials and thereby influence the level of neuronal excitability and modulate firing rates.

Stimulation with the negative pole (cathode) placed over a selected cortical region will decrease neuronal activity under the electrode whereas stimulation with the positive pole (anode) will increase neuronal activity under the electrode. In this manner, tDCS may be used to increase cortical brain activity in specific brain areas that are under aroused or alternatively decrease activity in areas that are overexcited. Research has shown that the effects of tDCS can last for an appreciable amount of time after exposure.

tDCS may sound similar to electroshock or electroconvulsive therapy (ECT) but it is quite different. ECT is done under anaesthesia and applies electrical currents a thousand times greater than tDCS to cause a seizure. ECT drastically affects the functioning of the entire brain and can result in significant adverse effects, including memory loss. Transcranial DC stimulation uses only very small electric currents that cannot set off a seizure and is far more selective in its effects. TDCS only influences the area of the cortical brain directly beneath the electrode.

tDCS may work in a way that is somewhat similar to transcranial magnetic stimulation (TMS) but is still quite different. In TMS, the brain is penetrated by a powerful pulsed magnetic field that causes all the neurons in the targeted area of the brain to fire in concert. After TMS stimulation stops, depending on the frequency of the magnetic pulses, the targeted region of the brain is either turned off or on. TMS devices are quite expensive and bulky which makes them difficult to use outside a hospital or large clinic. TMS can also set off seizures, so must be medically monitored. Where tDCS is quite different from TMS is that it only affects neurons that are already active—it does not cause resting neurons to fire. Moreover, the effects of tDCS appear to be limited to the cortex of the brain, whereas TMS can penetrate to deeper brain structures.

How is tDCS Administered?

Transcranial DC stimulation may be done in the doctor’s office with the patient sitting in a comfortable chair. The basic treatment consists of a series of five 20-minute sessions over five consecutive days, Monday through Friday. Sometimes a second series of five treatments may be necessary to obtain maximum improvement in symptoms being treated.

Illustration of a patient being treated with tDCS.

While the patient is seated in a chair, two 5 cm x 5 cm non-metallic conductive rubber electrodes are placed on selected locations of the scalp and covered by saline soaked sponges and held in place by elastic headbands. After the electrodes are properly placed, a tDCS device powered by a 9-volt battery is used to send a steady electrical current of 1-2 microamps through the electrodes and into the cortex for 20 minutes.

The electrode attached to the positive (anode) pole of the battery will excite neuronal activity in the cortex under it, whereas the electrode attached to the negative pole (cathode) of the battery will inhibit neuronal activity in the cortex under it.

The procedure does not elicit any pain. Patients receiving tDCS generally report nothing more than a mild tingling or itchy feeling from under the electrode during the stimulation. These sensations disappear immediately after the current is turned off.

Treatment with tDCS is relatively inexpensive, easy to administer, non-invasive, painless, and safe.

Transcranial DC Stimulation to Treat Depression

Fregni, et al. (2006) reports on a randomized, sham-controlled, clinical trial of tDCS in the treatment of 10 patients diagnosed with major depression. Level of depression was evaluated before and after treatment by means of the Hamilton Depression Rating Scale (HDRS) and Beck Depression Inventory (BDI). Patients were randomly assigned to one of two groups, an active treatment group that received 1.0 mA anodal (+) DC stimulation over the left dorsolateral prefrontal cortex (DLPFC) and cathodal (-) stimulation over the contralateral supraorbital area (just above right eyebrow) versus a sham treatment group that received the identical treatment but with the tDCS device turned off. Both groups received 20 minutes of actual or sham stimulation once a day for five consecutive days. All patients remained blind to treatment conditions and the treatment was well-tolerated with no significant adverse effects. Four of the five patients in the active treatment group were treatment responders whereas none of the five patients receiving sham were treatment responders. The active treatment group showed a significantly greater reduction in depression scores on the post-treatment HDRS and BDI as compared to the sham treatment group (70% vs 30% respectively).

Fregni, F., Boggio, P., Nitsche, M., et al. (2006). Letters to the Editor: Treatment of major depression with transcranial direct current stimulation. Bipolar Disorders, 8:203-205.

Boggio, et al. (2008) followed up and expanded on Fregni’s earlier small clinical trial by examining the effects of 2.0 mA tDCS treatment on major depression with a larger group of 40 unmedicated patients. In this study, the patients were randomly assigned to one of three groups in a 2:1:1 ratio: active treatment (n = 21), active control (n = 9), and sham treatment (n = 10). As with Fregni’s study, all patients were evaluated pre- and post-treatment using the HDRS and BDI depression scales but this time the scales were administered at the beginning of treatment (baseline), immediately after treatment, and at 15 and 30 days post-treatment.

All patients received ten 20-minute treatment sessions over a period of two weeks. The active treatment group was treated with anodal (+) tDCS over the left DLPFC. The active control group was treated with anodal (+) tDCS over the occipital cortex. The sham group was treated exactly as the active group but with the electricity turned off. In all cases, the cathode (-) was placed over the right eyebrow.  

Treatment response was defined as a 50% or greater reduction in HDRS scores from baseline. Remission was defined as HDRS scores below 7. On average, the active treatment group obtained a 40% reduction in HDRS scores with treatment as compared to 21% and 10% for the active control and sham groups respectively.

The results of this study demonstrated that ten brief sessions (10 x 20 minutes) of cortical stimulation with tDCS is associated with clinically significant reductions in depression scores on clinical symptom rating scales that is specific to the site of stimulation and lasts for at least 30 days post-treatment. Moreover, 10 days of tDCS treatment resulted in only minimal and temporary adverse effects in less than 15% of the patients that did not carry on beyond the end of treatment.

References

Boggio, P., Amancio, E., Correa, C., et al. (2009). Transcranial DC stimulation coupled with TENS for the treatment of chronic pain: A preliminary Study. Clinical Journal of Pain, 25:691-695.

Boggio, P., Nitsche, M., Pascual-Leone, A. (2005). Correspondance: Transcranial direct current stimulation. British Journal of Psychiatry, 186:446-447.

Boggio, P., Sultani, N., Fecteau, S., et al. (2008). Prefrontal cortex modulation using transcranial DC stimulation reduces alcohol craving: A double-blind, sham-controlled study. Drug & Alcohol Dependancy, 92(1-3):55-60.

Fregni, F., Boggio, P., Nitsche, M., et al. (2006). Letters to the Editor: Treatment of major depression with transcranial direct current stimulation. Bipolar Disorders, 8:203-205.

Fregni, F., Gimenez, R., Vallc, A., et al. (2006). A randomized sham-controlled, proof of principle study of transcranial direct current stimulation for the treatment of fibromyalgia. Arthritis & Rheumatism, 54(12):3968-3998.

Fregni, F., Pascual-Leone, A., et al. (2007). Technology Insight: Non-invasive brain stimulation in neurology - Perspectives on the therapeutic potential of rTMS and tDCS. Clinical Practice in Neurology, 3(7):383.

Iyer, M., Mattu, U., Grafman, J., et al. (2005). Safety and cognitive effects of frontal DC brain polarization in healthy individuals. Neurology, 64(5):872-875.

Lefaucheur, J-P., Antal, A., Ahdab, R., et al. (2008). The use of repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) to relieve pain. Brain Stimulation, 1:337-344.

Mori, F., Codeca, C., Kusayanagi, H., et al., (2009). Effects of anodal transcranial direct current stimulation on chronic neuropathic pain in patients with multiple sclerosis. The Journal of Pain, December 2009.

Nitsche, M. & Paulus, W. (2000). Excitability changes induced in the human motor cortex by weak transcranial direct current stimulation. Journal of Physiology, 527(3):633-639.

Rigonatti, S., Boggio, P., Myczkowski, M., et al. (2008). Letters to the Editor: Transcranial direct current stimulation and fluoxetine for treatment of depression. European Psychiatry, 23:74-76.

Roizenblatt, S., Fregni, F., Gimenez, R., et al. (2007). Site-specific effects of transcranial direct current stimulation on sleep and pain in fibromyalgia: A randomized, sham -controlled study. Pain Practice, 7(4):297-306.

 

Treating Chronic Pain With Direct Current Stimulation

(CBS) There's new hope for people suffering from chronic pain, and that's the focus of our new series, "Easing the Pain." For the first installment, CBS News medical correspondent Dr. Jon LaPook examines a way to cut pain without using medication - instead, it employs an ancient technique: applying electricity.

 

When Detective Thomas Tobin was busting bad guys for the New York City Police, he never imagined that his toughest adversary would turn out to be... pain.

"What I usually have constantly is a dull aching crushing pain like deep in my bones, as if my shin is in a vice or somebody is standing on my foot," he told CBS News medical correspondent Dr. Jon LaPook.

I all started 10 years ago after an operation for a knee injury.  "It was life-changing. I went from working constantly to not working at all," he said. For years, his only relief was a cocktail of prescribed medications. "I take about 35 pills a day," he said. "Every day."

Now he's trying something that might seem shocking: an electrical current applied to his head - part of a clinical trial at Beth Israel Medical Center in New York. It's called tDCS, Transcranial Direct Current Stimulation. A small electrical current seems to work by affecting pain centers deep within the brain, somehow muffling the perception of pain. The main side effect so far is slight scalp irritation.

Tobin doesn't feel a shock, just a tingling sensation.

"In some way that nobody understands and still seems rather magical, pain might be reduced," said Dr. Russell Portenoy.

The idea dates back 2,000 years, when a Roman physician found he could relieve gout and headache by placing an electric fish on the scalp.

Since then, the technique has been refined. "It's very early," Portenoy said. "And we don't know how effective it will be. We think it will be very safe."

Thirty years ago, electrodes were surgically implanted deep within the brain. Years later, on the surface. This new approach places them right on the scalp. This kind of surface stimulation has shown promise in small studies of patients with fibromyalgia and spinal cord injury.

"The idea is when you get the treatment and it is successful and the pain gets better then you can start cutting down the on the medication, and see how low you can go" said Dr. Richard Cruciani.

Every few months, Tobin gets treatments 20 minutes a day for five days. He says his pain drops significantly after therapy and then slowly returns over time. "I am in a lot less pain today and now it just feels as though I have a sunburn that is a few days old," he said.

This therapy is being tested at several centers around the world and more study is needed, but this new variation on an ancient concept is promising -- using electricity to try to zap the perception of pain.

Could this could work for all kinds of pain?

"That's the hope," says Lapook. "Whatever the cause, it dials down the pain on the brain center. With chronic pain you have to throw the kitchen sink at it. That means integrative medicine, acupuncture, massage, medication in as low doses as possible.

Annotated Bibliography

Transcranial DC Stimulation to Treat Depression

Bipolar Disorders. 2002;4 Suppl 1:98-9.

Transcranial direct current stimulation: a new treatment for depression?

Nitsche MA.

Department Clin. Neurophysiology, Georg-August-University, Goettingen, Germany.

PMID: 12479691 [PubMed - indexed for MEDLINE]

 

Depression & Anxiety. 2006;23(8):482-4.

Cognitive effects of repeated sessions of transcranial direct current stimulation in patients with depression.

Fregni F, Boggio PS, Nitsche MA, Rigonatti SP, Pascual-Leone A.

PMID: 16845648 [PubMed - indexed for MEDLINE]

 

Bipolar Disorders. 2006 Apr;8(2):203-4.

Treatment of major depression with transcranial direct current stimulation.

Fregni F, Boggio PS, Nitsche MA, Marcolin MA, Rigonatti SP, Pascual-Leone A.

PMID: 16542193 [PubMed - indexed for MEDLINE]

 

International Journal of Neuropsychopharmacology. 2008 Mar;11(2):249-54.

A randomized, double-blind clinical trial on the efficacy of cortical direct current stimulation for the treatment of major depression.

Boggio PS, Rigonatti SP, Ribeiro RB, Myczkowski ML, Nitsche MA, Pascual-Leone A,  Fregni F.

Núcleo de Neurociências, Centro de Ciências Biológicas e da Saúde, Universidade Presbiteriana Mackenzie, Sao Paulo, Brazil. boggio@usp.br

Preliminary findings suggest that transcranial direct current stimulation (tDCS)  can have antidepressant effects. We sought to test this further in a parallel-group, double-blind clinical trial with 40 patients with major depression, medication-free randomized into three groups of treatment: anodal tDCS of the left dorsolateral prefrontal cortex (active group - 'DLPFC'); anodal  tDCS of the occipital cortex (active control group - 'occipital') and sham tDCS (placebo control group - 'sham'). tDCS was applied for 10 sessions during a 2-wk  period. Mood was evaluated by a blinded rater using the Hamilton Depression Rating Scale (HDRS) and Beck Depression Inventory (BDI). The treatment was well tolerated with minimal side-effects that were distributed equally across all treatment groups. We found significantly larger reductions in depression scores after DLPFC tDCS [HDRS reduction of 40.4% (+/-25.8%)] compared to occipital [HDRS reduction of 21.3% (+/-12.9%)] and sham tDCS [HDRS reduction of 10.4% (+/-36.6%)]. The beneficial effects of tDCS in the DLPFC group persisted for 1 month after the end of treatment. Our findings support further investigation on the effects of this novel potential therapeutic approach - tDCS - for the treatment of major depression.

PMID: 17559710 [PubMed - indexed for MEDLINE]

 

Current Treatment Options in Neurology. 2008 Sep;10(5):377-85.

Transcranial direct current stimulation for major depression: a general system for quantifying transcranial electrotherapy dosage.

Bikson M, Bulow P, Stiller JW, Datta A, Battaglia F, Karnup SV, Postolache TT.

Teodor T. Postolache, MD Mood and Anxiety Program, University of Maryland School  of Medicine, 685 West Baltimore, MSTF Suite 930, Baltimore, MD 21201, USA. Tpostola@psych.umaryland.edu.

There has been a recent resurgence of interest in therapeutic modalities using transcranial weak electrical stimulation through scalp electrodes, such as trans-cranial direct current stimulation (tDCS), as a means of experimentally modifying and studying brain function and possibly treating psychiatric conditions. A range of electrotherapy paradigms have been investigated, but no consistent method has been indicated for reporting reproducible stimulation "dosage." Anecdotal reports, case studies, and limited clinical trials with small numbers suggest that tDCS may be effective in treating some patients with depression, but methods for selecting the optimal stimulation parameters ("dosage") are not clear, and there is no conclusive indication that tDCS is an effective treatment for depression. Larger, controlled studies are necessary to determine its safety and efficacy in a clinical setting. If tDCS can be established as an effective treatment for depression, it would represent a particularly attractive electrotherapy option, as it is a relatively benign and affordable treatment modality. An accurate system for describing reproducible treatment parameters is essential so that further studies can yield evidence-based guidelines for the clinical use of transcranial current stimulation. Development of appropriate parameters requires a biophysical understanding of how electrotherapy affects brain function and should include different paradigms for different clinical applications. As with any dosage guidelines, such a system does not supersede physician judgment on safety.

PMID: 18782510 [PubMed - in process]

 

Transcranial DC Stimulation to Treat Pain

 Pain. 2006 May;122(1-2):197-209.

Comment in: Pain. 2006 May;122(1-2):11-3.

A sham-controlled, phase II trial of transcranial direct current stimulation for  the treatment of central pain in traumatic spinal cord injury.

Fregni F, Boggio PS, Lima MC, Ferreira MJ, Wagner T, Rigonatti SP, Castro AW, Souza DR, Riberto M, Freedman SD, Nitsche MA, Pascual-Leone A.

Harvard Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA. ffregni@bidmc.harvard.edu

Past evidence has shown that motor cortical stimulation with invasive and non-invasive brain stimulation is effective to relieve central pain. Here we aimed to study the effects of another, very safe technique of non-invasive brain  stimulation--transcranial direct current stimulation (tDCS)--on pain control in patients with central pain due to traumatic spinal cord injury. Patients were randomized to receive sham or active motor tDCS (2mA, 20 min for 5 consecutive days). A blinded evaluator rated the pain using the visual analogue scale for pain, Clinician Global Impression and Patient Global Assessment. Safety was assessed with a neuropsychological battery and confounders with the evaluation of depression and anxiety changes. There was a significant pain improvement after active anodal stimulation of the motor cortex, but not after sham stimulation. These results were not confounded by depression or anxiety changes. Furthermore,  cognitive performance was not significantly changed throughout the trial in both  treatment groups. The results of our study suggest that this new approach of cortical stimulation can be effective to control pain in patients with spinal cord lesion. We discuss potential mechanisms for pain amelioration after tDCS, such as a secondary modulation of thalamic nuclei activity.

PMID: 16564618 [PubMed - indexed for MEDLINE]

 

Pain Practice. 2007 Dec;7(4):297-306.

Site-specific effects of transcranial direct current stimulation on sleep and pain in fibromyalgia: a randomized, sham-controlled study.

Roizenblatt S, Fregni F, Gimenez R, Wetzel T, Rigonatti SP, Tufik S, Boggio PS, Valle AC.

Department of Psychobiology, Universidade Federal de São Paulo, São Paulo, Brazil.

OBJECTIVE: To investigate whether active anodal transcranial direct current stimulation (tDCS) (of dorsolateral prefrontal cortex [DLPFC] and primary motor cortex [M1]) as compared to sham treatment is associated with changes in sleep structure in fibromyalgia. METHODS: Thirty-two patients were randomized to receive sham stimulation or active tDCS with the anode centered over M1 or DLPFC  (2 mA, 20 minutes for five consecutive days). A blinded evaluator rated the clinical symptoms of fibromyalgia. All-night polysomnography was performed before and after five consecutive sessions of tDCS. RESULTS: Anodal tDCS had an effect on sleep and pain that was specific to the site of stimulation: such as that M1 and DLPFC treatments induced opposite effects on sleep and pain, whereas sham stimulation induced no significant sleep or pain changes. Specifically, whereas M1 treatment increased sleep efficiency (by 11.8%, P = 0.004) and decreased arousals (by 35.0%, P = 0.001), DLPFC stimulation was associated with a decrease  in sleep efficiency (by 7.5%, P = 0.02), an increase in rapid eye movement (REM)  and sleep latency (by 47.7%, P = 0.0002, and 133.4%, P = 0.02, respectively). In  addition, a decrease in REM latency and increase in sleep efficiency were associated with an improvement in fibromyalgia symptoms (as indexed by the Fibromyalgia Impact Questionnaire). Finally, patients with higher body mass index had the worse sleep outcome as indexed by sleep efficiency changes after M1 stimulation. INTERPRETATION: Our findings suggest that one possible mechanism to  explain the therapeutic effects of tDCS in fibromyalgia is via sleep modulation that is specific to modulation of primary M1 activity.

PMID: 17986164 [PubMed - indexed for MEDLINE]

 

Cephalalgia. 2007 Jul;27(7):833-9.

Transcranial direct current stimulation reveals inhibitory deficiency in migraine.

Chadaide Z, Arlt S, Antal A, Nitsche MA, Lang N, Paulus W.

Department of Clinical Neurophysiology, Georg-August University, Göttingen, Germany.

The issue of interictal excitability of cortical neurons in migraine patients is  controversial: some studies have reported hypo-, others hyperexcitability. The aim of the present study was to observe the dynamics of this basic interictal state by further modulating the excitability level of the visual cortex using transcranial direct current stimulation (tDCS) in migraineurs with and without aura. In healthy subjects anodal tDCS decreases, cathodal stimulation increases transcranial magnetic stimulation (TMS)-elicited phosphene thresholds (PT), which is suggested as a representative value of visual cortex excitability. Compared with healthy controls, migraine patients tended to show lower baseline PT values, but this decrease failed to reach statistical significance. Anodal stimulation decreased phosphene threshold in migraineurs similarly to controls, having a larger effect in migraineurs with aura. Cathodal stimulation had no significant effect in the patient groups. This result strengthens the notion of deficient inhibitory processes in the cortex of migraineurs, which is selectively revealed  by activity-modulating cortical input.

PMID: 17498207 [PubMed - indexed for MEDLINE]

 

Lancet Neurology. 2007 Feb;6(2):188-91.

Recent advances in the treatment of chronic pain with non-invasive brain stimulation techniques.

Fregni F, Freedman S, Pascual-Leone A.

Center for Non-invasive Brain Stimulation, Department of Neurology, Harvard Medical School, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston 02115, USA. ffregni@bidmc.harvard.edu

BACKGROUND: Brain stimulation is a technique that can guide brain plasticity and  thus be suitable to treat chronic pain-a disorder that is associated with substantial reorganisation of CNS activity. In fact, the idea of using invasive and non-invasive brain stimulation for pain relief is not new. Studies from the 1950s investigated the use of this therapeutic method for the treatment of chronic pain. However, recent advancements in the techniques of non-invasive brain stimulation have enhanced their modulatory effects and thus become a new, attractive alternative for chronic pain treatment. RECENT DEVELOPMENTS: Recent studies with non-invasive brain stimulation--eg, repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS)--using new  parameters of stimulation have shown encouraging results. These studies explored  alternative sites of stimulation, such as the secondary somatosensory cortex (rather than primary motor cortex) for the treatment of chronic visceral pain and new parameters of stimulation, such as repeated sessions of tDCS with 2 mA for the treatment of chronic central pain. WHERE NEXT?: The investigation of non-invasive brain stimulation for therapeutic effects is in its at initial stages; but the preliminary data make us optimistic. Several questions still need to be addressed before any firm conclusion about this therapy is made. Other parameters of stimulation need to be further explored such as theta-burst stimulation and the combination of tDCS and rTMS. The duration of the therapeutic effects is another important issue to be considered, especially because the current devices for brain stimulation do not allow patients to receive this therapy in their homes; therefore, maintenance therapy regimens, as well as the development of portable stimulators, need to be investigated. Further trials must determine the optimum parameters of stimulation. After that, confirmatory, larger studies are mandatory.

PMID: 17239806 [PubMed - indexed for MEDLINE]

 

Clinical Journal of Pain. 2008 Jan;24(1):56-63.

Transcranial direct current stimulation over somatosensory cortex decreases experimentally induced acute pain perception.

Antal A, Brepohl N, Poreisz C, Boros K, Csifcsak G, Paulus W.

Department of Clinical Neurophysiology, Georg-August University, Robert Koch Strasse 40, 37075 Göttingen, Germany. AAntal@gwdg.de

OBJECTIVE: Multiple cortical areas including the primary somatosensory cortex are known to be involved in nociception. The aim of this study was to investigate the effect of transcranial direct current stimulation (tDCS) that modulates the cortical excitability painlessly and noninvasively, over somatosensory cortex on  acute pain perception induced with a Tm:YAG laser. METHODS: Subjective pain rating scores and amplitude changes of the N1, N2, and P2 components of laser-evoked potentials of 10 healthy participants were analyzed before and after anodal, cathodal, and sham tDCS. RESULTS: Our results demonstrate that cathodal tDCS significantly diminished pain perception and the amplitude of the N2 component when the contralateral hand to the side of tDCS was laser-stimulated, whereas anodal and sham stimulation conditions had no significant effect. DISCUSSION: Our study highlights the antinociceptive effect of this technique and may contribute to the understanding of the mechanisms underlying pain relief. The pharmacologic prolongation of the excitability-diminishing after-effects would render the method applicable to different patient populations with chronic pain.

PMID: 18180638 [PubMed - indexed for MEDLINE]

 

European Journal of Neurology. 2008 Oct;15(10):1124-30.

Modulatory effects of anodal transcranial direct current stimulation on perception and pain thresholds in healthy volunteers.

Boggio PS, Zaghi S, Lopes M, Fregni F.

Berenson-Allen Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA.

BACKGROUND AND PURPOSE: We aimed to evaluate whether transcranial direct current  stimulation (tDCS) is effective in modulating sensory and pain perception thresholds in healthy subjects as to further explore mechanisms of tDCS in pain relief. METHODS: Twenty healthy subjects received stimulation with tDCS under four different conditions of stimulation: anodal tDCS of the primary motor cortex (M1), dorsolateral prefrontal cortex (DLPFC), occipital cortex (V1), and sham tDCS. The order of conditions was randomized and counterbalanced across subjects. Perception threshold and pain threshold to peripheral electrical stimulation of the right index finger were evaluated by a blinded rater. RESULTS: The results showed a significant effect of the interaction time versus stimulation condition  for perception (P = 0.046) and pain threshold (P = 0.015). Post hoc comparisons revealed that anodal stimulation of M1 increased both perception (P < 0.001, threshold increase of 6.5%) and pain (P = 0.001, threshold increase of 8.3%) thresholds significantly, whilst stimulation of the DLPFC increased pain threshold only (P = 0.046, threshold increase of 10.0%). There were no significant effects for occipital or sham stimulation. CONCLUSIONS: These results show that both M1 and DLFPC anodal tDCS can be used to modulate pain thresholds in healthy subjects; thus, the mechanism of tDCS in modulating pain involves pathways that are independent of abnormal pain-related neural activity.

PMID: 18717717 [PubMed - in process]

 

Neuropsychologia. 2009 Jan;47(1):212-217.

Modulation of emotions associated with images of human pain using anodal transcranial direct current stimulation (tDCS).

Boggio PS, Zaghi S, Fregni F.

Berenson-Allen Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, USA; Programa de Pós-Graduação em Distúrbios do Desenvolvimento e Núcleo de Neurociências do Comportamento, Centro  de Ciências Biológicas e da Saúde, Universidade Presbiteriana Mackenzie, São Paulo, Brazil.

Viewing images of other humans in pain elicits a variety of responses including distress, anxiety, and a sensation that is similar to pain. We aimed to evaluate  whether transcranial direct current stimulation (tDCS) could be effective in modulating the emotional aspects of pain as to further explore mechanisms of tDCS in pain relief. Twenty-three healthy subjects rated images with respect to unpleasantness and discomfort/pain (baseline), and then received stimulation with tDCS under four different conditions of stimulation: anodal tDCS of the left primary motor cortex (M1), dorsolateral prefrontal cortex (DLPFC), occipital cortex (V1); and sham tDCS. The order of conditions was randomized and counterbalanced across subjects. During each stimulation session (after 3min of stimulation), subjects were shown a new set of aversive images and were again asked to rate the images with respect to unpleasantness and discomfort/pain. The  results showed that ratings of unpleasantness and discomfort/pain were significantly decreased during DLPFC tDCS only, as compared to baseline and sham  tDCS. The other conditions of stimulation (M1 and V1 tDCS) did not result in any  significant changes. These results support the notion that DLPFC is a critical area for the emotional processing of pain and also suggests that DLPFC may be a potential target of stimulation for alleviation of pain with a significant emotional-affective component. Our results also suggest that the mechanism of tDCS in modulating emotional pain involve pathways that are independent of those  modulating the somatosensory perception of pain.

PMID: 18725237 [PubMed - as supplied by publisher]

 

Current Pain Headache Report. 2009 Feb;13(1):12-7.

Noninvasive transcranial brain stimulation and pain.

Rosen AC, Ramkumar M, Nguyen T, Hoeft F.

Palo Alto Veterans Affairs Health Care System, 3801 Miranda Avenue (151Y), Palo Alto, CA 94304-1207, USA. rosena@psych.stanford.edu

Transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) are two noninvasive brain stimulation techniques that can modulate activity in specific regions of the cortex. At this point, their use in  brain stimulation is primarily investigational; however, there is clear evidence  that these tools can reduce pain and modify neurophysiologic correlates of the pain experience. TMS has also been used to predict response to surgically implanted stimulation for the treatment of chronic pain. Furthermore, TMS and tDCS can be applied with other techniques, such as event-related potentials and pharmacologic manipulation, to illuminate the underlying physiologic mechanisms of normal and pathological pain. This review presents a description and overview  of the uses of two major brain stimulation techniques and a listing of useful references for further study.

PMID: 19126365 [PubMed - in process]

 

Transcranial DC Stimulation in Stroke Recovery

Neuroreport.2005 Sep 28;16(14):1551-5.

Transcranial direct current stimulation of the unaffected hemisphere in stroke patients.

Fregni F, Boggio PS, Mansur CG, Wagner T, Ferreira MJ, Lima MC, Rigonatti SP, Marcolin MA, Freedman SD, Nitsche MA, Pascual-Leone A.

Harvard Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA. ffregni@bidmc.harvard.edu

Recovery of function after a stroke is determined by a balance of activity in the neural network involving both the affected and the unaffected brain hemispheres.  Increased activity in the affected hemisphere can promote recovery, while excessive activity in the unaffected hemisphere may represent a maladaptive strategy. We therefore investigated whether reduction of the excitability in the  unaffected hemisphere by cathodal transcranial direct current stimulation could result in motor performance improvement in stroke patients. We compared these results with excitability-enhancing anodal transcranial direct current stimulation of the affected hemisphere and sham transcranial direct current stimulation. Both cathodal stimulation of the unaffected hemisphere and anodal stimulation of the affected hemisphere (but not sham transcranial direct current  stimulation) improved motor performance significantly. These results suggest that the appropriate modulation of bihemispheric brain structures can promote motor function recovery.

PMID: 16148743 [PubMed - indexed for MEDLINE]

 

Lancet Neurology. 2006 Aug;5(8):708-12.

Non-invasive brain stimulation: a new strategy to improve neurorehabilitation after stroke?

Hummel FC, Cohen LG.

Human Cortical Physiology Section and Stroke Neurorehabilitation Clinic, National Institute of Neurological Disorders and Stroke, National Institute of Health, Bethesda 20817, USA.

BACKGROUND: Motor impairment resulting from chronic stroke can have extensive physical, psychological, financial, and social implications despite available neurorehabilitative treatments. Recent studies in animals showed that direct epidural stimulation of the primary motor cortex surrounding a small infarct in the lesioned hemisphere (M1(lesioned hemisphere)) elicits improvements in motor function. RECENT DEVELOPMENTS: In human beings, proof of principle studies from different laboratories showed that non-invasive transcranial magnetic stimulation and direct current stimulation that upregulate excitability within M1(lesioned hemisphere) or downregulate excitability in the intact hemisphere (M1(intact hemisphere)) results in improvement in motor function in patients with stroke. Possible mechanisms mediating these effects can include the correction of abnormally persistent interhemispheric inhibitory drive from M1(intact hemisphere) to M1(lesioned hemisphere) in the process of generation of voluntary  movements by the paretic hand, a disorder correlated with the magnitude of impairment. In this paper we review these mechanistically oriented interventional approaches. WHAT NEXT?: These findings suggest that transcranial magnetic stimulation and transcranial direct current stimulation could develop into useful adjuvant strategies in neurorehabilitation but have to be further assessed in multicentre clinical trials.

PMID: 16857577 [PubMed - indexed for MEDLINE]

 

Current Opinion in Neurology. 2006 Dec;19(6):543-50.

Does brain stimulation after stroke have a future?

Talelli P, Rothwell J.

Sobell Department, Institute of Neurology, Queen Square, London, UK.

PURPOSE OF REVIEW: Transcranial methods of cortical stimulation can induce long-term changes in excitability of the cerebral cortex in humans and may be useful as therapeutic interventions in stroke rehabilitation. RECENT FINDINGS: Two approaches have been tested: (1) increasing excitability of the cortex in the stroke hemisphere and (2) suppression of the non-stroke hemisphere to reduce potential interference with function of the stroke hemisphere. The interventions  have been transcranial direct current stimulation, transcranial magnetic stimulation and implanted epidural stimulation. All have been reported to give 10-20% functional improvement in small numbers of patients in single-session studies as well as in a small number of longer-term therapeutic trials. Preliminary experiments in aphasic patients using transcranial magnetic stimulation in an interference design show, however, that stimulation of the nonstroke hemisphere can in some patients reduce verbal fluency, questioning the  general applicability of the second approach. SUMMARY: Cortical stimulation appears to be a safe and promising intervention for stroke patients. More studies are needed to assess its long-term benefits on substantial numbers of patients. We need to know what type of intervention is best, which patients are likely to benefit, the optimum time to intervene and the duration of any benefits.

PMID: 17102691 [PubMed - indexed for MEDLINE]

 

Restorative Neurology & Neuroscience. 2007;25(2):123-9.

Repeated sessions of noninvasive brain DC stimulation is associated with motor function improvement in stroke patients.

Boggio PS, Nunes A, Rigonatti SP, Nitsche MA, Pascual-Leone A, Fregni F.

Department of Experimental Psychology and Department of Psychiatry, University of Sao Paulo, Sao Paulo, Brazil.

PURPOSE: Recent evidence has suggested that a simple technique of noninvasive brain stimulation - transcranial direct current stimulation (tDCS) - is associated with a significant motor function improvement in stroke patients. METHODS: We tested the motor performance improvement in stroke patients following 4 weekly sessions of sham, anodal- and cathodal tDCS (experiment 1) and the effects of 5 consecutive daily sessions of cathodal tDCS (experiment 2). A blinded rater evaluated motor function using the Jebsen-Taylor Hand Function Test. RESULTS: There was a significant main effect of stimulation condition (p=0.009) in experiment 1. Furthermore there was a significant motor function improvement after either cathodal tDCS of the unaffected hemisphere (p=0.016) or  anodal tDCS of the affected hemisphere (p=0.046) when compared to sham tDCS. There was no cumulative effect associated with weekly sessions of tDCS, however consecutive daily sessions of tDCS (experiment 2) were associated with a significant effect on time (p< 0.0001) that lasted for 2 weeks after treatment. CONCLUSIONS: The findings of our study support previous research showing that tDCS is significantly associated with motor function improvement in stroke patients; and support that consecutive daily sessions of tDCS might increase its  behavioral effects. Because the technique of tDCS is simple, safe and non-expensive; our findings support further research on the use of this technique for the rehabilitation of patients with stroke.

PMID: 17726271 [PubMed - indexed for MEDLINE]

 

Cerebrovascular Diseases. 2007;24 Suppl 1:157-66. Epub 2007 Nov 1.

Brain stimulation in poststroke rehabilitation.

Alonso-Alonso M, Fregni F, Pascual-Leone A.

Berenson-Allen Center for Noninvasive Brain Stimulation, Behavioral Neurology Unit, Department of Neurology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Mass., USA.

Brain stimulation techniques provide a powerful means to modulate the function of specific neural structures, and show potential for future applications in the rehabilitation of stroke patients. Recent studies have started to translate to the bedside the body of data gathered over the last few years on mechanisms underlying brain plasticity and stroke recovery. Both noninvasive and invasive brain stimulation techniques, such as repetitive transcranial magnetic stimulation, transcranial direct current stimulation and direct cortical stimulation with epidural electrodes, have recently been tested in small studies  with stroke patients. The results to date are very promising. Nonetheless, we are still at an early stage in the field and further evidence is needed to assess the clinical impact of this new approach. In this review, we provide readers with a basic introduction to the field, summarize preliminary studies and discuss future directions. Copyright 2007 S. Karger AG, Basel.

PMID: 17971652 [PubMed - indexed for MEDLINE]

 

Archives of Neurology. 2008 Dec;65(12):1571-6.

Transcranial direct current stimulation in stroke recovery.

Schlaug G, Renga V, Nair D.

Neuroimaging and Stroke Recovery Laboratories, Department of Neurology, Beth Israel Deaconess Medical Center and Harvard Medical School, 330 Brookline Ave, Boston, MA 02215, USA. gschlaug@bidmc.harvard.edu

Transcranial direct current stimulation (TDCS)is an emerging technique of noninvasive brain stimulation that has been found useful in examining cortical function in healthy subjects and in facilitating treatments of various neurologic disorders. A better understanding of adaptive and maladaptive poststroke neuroplasticity and its modulation through noninvasive brain stimulation has opened up experimental treatment options using TDCS for patients recovering from  stroke. We review the role of TDCS as a facilitator of stroke recovery, the different modes of TDCS, and the potential mechanisms underlying the neural effects of TDCS.

PMID: 19064743 [PubMed - in process]

 

Expert Reviews of Medical Devices. 2008 Nov;5(6):759-768.

Transcranial direct current stimulation: a noninvasive tool to facilitate stroke  recovery.

Schlaug G, Renga V.

Department of Neurology, Neuroimaging and Stroke Recovery Laboratories, Beth Israel Deaconess Medical Center and Harvard Medical School, 330 Brookline Avenue, Boston, MA 02215, USA. gschlaug@bidmc.harvard.edu , Department of Neurology, Neuroimaging and Stroke Recovery Laboratories, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA.

Electrical brain stimulation, a technique developed many decades ago and then largely forgotten, has re-emerged recently as a promising tool for experimental neuroscientists, clinical neurologists and psychiatrists in their quest to causally probe cortical representations of sensorimotor and cognitive functions and to facilitate the treatment of various neuropsychiatric disorders. In this regard, a better understanding of adaptive and maladaptive plasticity in natural  stroke recovery over the last decade and the idea that brain polarization may modulate neuroplasticity has led to the use of transcranial direct current stimulation (tDCS) as a potential enhancer of natural stroke recovery. We will review tDCS's successful utilization in pilot and proof-of-principle stroke recovery studies, the different modes of tDCS currently in use, and the potential mechanisms underlying the neural effects of tDCS.

PMID: 19025351 [PubMed - as supplied by publisher]

 

Neurosciences Letters. 2008 Dec 26;448(2):171-4. Epub 2008 Oct 21.

Improvement of visual scanning after DC brain polarization of parietal cortex in  stroke patients with spatial neglect.

Ko MH, Han SH, Park SH, Seo JH, Kim YH.

Department of Physical Medicine and Rehabilitation, Institute for Medical Sciences & Research Institute of Clinical Medicine, Chonbuk National University Medical School, 634-18 Keumam-dong, Dukjin-ku, Jeonju, Jeonbuk 561-712, Republic  of Korea.

Previous studies have demonstrated that transcranial direct current (DC) brain polarization can modulate cortical excitability in the human brain. We investigated the effect of anodal DC brain polarization of right parietal cortex  on visuospatial scanning in subacute stroke patients with spatial neglect. The patients underwent two neglect tests - figure cancellation and line bisection - before and immediately after anodal DC or sham in a double-blind protocol. Anodal DC was applied to the scalp over the right posterior parietal cortex (PPC) with an intensity of 2.0mA for 20min. Anodal DC brain polarization, but not sham, led  to significant improvement in the both neglect tests. These results document a beneficial effect of DC brain polarization on neglect.

PMID: 18952147 [PubMed - in process]

 

Transcranial DC Stimulation for Substance Abuse and Craving

 

Drug & Alcohol Dependency. 2008 Jan 1;92(1-3):55-60. Epub 2007 Jul 19.

Prefrontal cortex modulation using transcranial DC stimulation reduces alcohol craving: a double-blind, sham-controlled study.

Boggio PS, Sultani N, Fecteau S, Merabet L, Mecca T, Pascual-Leone A, Basaglia A, Fregni F.

Nucleo de Neurociencias, Mackenzie University, Sao Paulo, SP, Brazil.

BACKGROUND: Functional neuroimaging studies have shown that specific brain areas  are associated with alcohol craving including the dorsolateral prefrontal cortex  (DLPFC). We tested whether modulation of DLPFC using transcranial direct current  stimulation (tDCS) could alter alcohol craving in patients with alcohol dependence while being exposed to alcohol cues. METHODS: We performed a randomized sham-controlled study in which 13 subjects received sham and active bilateral tDCS delivered to DLPFC (anodal left/cathodal right and anodal right/cathodal left). For sham stimulation, the electrodes were placed at the same positions as in active stimulation; however, the stimulator was turned off after 30s of stimulation. Subjects were presented videos depicting alcohol consumption to increase alcohol craving. RESULTS: Our results showed that both anodal left/cathodal right and anodal right/cathodal left significantly decreased alcohol craving compared to sham stimulation (p<0.0001). In addition, we found that following treatment, craving could not be further increased by alcohol cues. CONCLUSIONS: Our findings showed that tDCS treatment to DLPFC can reduce alcohol  craving. These findings extend the results of previous studies using noninvasive  brain stimulation to reduce craving in humans. Given the relatively rapid suppressive effect of tDCS and the highly fluctuating nature of alcohol craving,  this technique may prove to be a valuable treatment strategy within the clinical  setting.

PMID: 17640830 [PubMed - indexed for MEDLINE]

 

Journal of Clinical Psychiatry. 2008 Jan;69(1):32-40.

Cortical stimulation of the prefrontal cortex with transcranial direct current stimulation reduces cue-provoked smoking craving: a randomized, sham-controlled study.

Fregni F, Liguori P, Fecteau S, Nitsche MA, Pascual-Leone A, Boggio PS.

Berenson-Allen Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Mass. 02215, USA. ffregni@bidmc.harvard.edu

OBJECTIVE: Because neuroimaging studies have shown that cue-provoked smoking craving is associated with changes in the activity of the bilateral dorsolateral  prefrontal cortex (DLPFC), we aimed to investigate whether a powerful technique of noninvasive brain stimulation, transcranial direct current stimulation (tDCS), reduces cue-provoked smoking craving as indexed by a visual analog scale. METHOD: We performed a randomized, sham-controlled crossover study in which 24 subjects received sham and active tDCS (anodal tDCS of the left and right DLPFC) in a randomized order. Craving was induced by cigarette manipulation and exposure to a smoking video. The study ran from January 2006 to October 2006. RESULTS: Smoking  craving was significantly increased after exposure to smoking-craving cues (p < .0001). Stimulation of both left and right DLPFC with active, but not sham, tDCS  reduced craving significantly when comparing craving at baseline and after stimulation, without (p = .007) and with (p = .005) smoking-craving cues. There were no significant mood changes in any of the conditions of stimulation. Adverse events were mild and distributed equally across all treatment conditions. CONCLUSIONS: Our findings extend the results of a previous study on the use of brain stimulation to reduce craving, showing that cortical stimulation with tDCS  is beneficial for reducing cue-provoked craving, and thus support the further exploration of this technique for smoking cessation.

PMID: 18312035 [PubMed - indexed for MEDLINE]

 

Appetite. 2008 Jul;51(1):34-41.

Transcranial direct current stimulation of the prefrontal cortex modulates the desire for specific foods.

Fregni F, Orsati F, Pedrosa W, Fecteau S, Tome FA, Nitsche MA, Mecca T, Macedo EC, Pascual-Leone A, Boggio PS.

Berenson-Allen Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue #KS 454, Boston, MA, 02215, USA. ffregni@bidmc.harvard.edu

We aimed to assess whether modulation of the dorsolateral prefrontal cortex (DLFPC) with noninvasive brain stimulation, namely transcranial direct current stimulation (tDCS), modifies food craving in healthy subjects. We performed a randomized sham-controlled cross-over study in which 23 subjects received sham and active tDCS (anode left/cathode right and anode right/cathode left) of the DLPFC. Subjects were exposed to food and also watched a movie of food associated  with strong craving. Desire for food consumption was evaluated by visual analogue scales (VAS) and food consumption before and after treatment. In addition we measured visual attention to food using an eye tracking system. Craving for viewed foods as indexed by VAS was reduced by anode right/cathode left tDCS. After sham stimulation, exposure to real food or food-related movie increased craving; whereas after anode left/cathode right tDCS, the food-related stimuli did not increase craving levels, as revealed by the VAS scale. Moreover, compared with sham stimulation, subjects fixated food-related pictures less frequently after anode right/cathode left tDCS and consumed less food after both active stimulation conditions. These changes were not related to mood changes after any  type of tDCS treatment. The effects of tDCS on food craving might be related to a modulation of neural circuits associated with reward and decision-making.

PMID: 18243412 [PubMed - indexed for MEDLINE]

 

Transcranial DC Stimulation Effects and Safety

 

Neuroreport. 1998 Jul 13;9(10):2257-60.

Polarization of the human motor cortex through the scalp.

Priori A, Berardelli A, Rona S, Accornero N, Manfredi M.

Dipartimento di Scienze Neurologiche, Università degli Studi di Roma La Sapienza, Italy.

Direct currents (DC) applied directly to central nervous system structures produce substantial and long-lasting effects in animal experiments. We tested the functional effects of very weak scalp DC (< 0.5 mA, 7 s) on the human motor cortex by assessing the changes in motor potentials evoked by transcranial magnetic brain stimulation. We performed four different experiments in 15 healthy volunteers. Our findings led to the conclusion that such weak (< 0.5 mA) anodal scalp DC, alternated with a cathodal DC, significantly depresses the excitability of the human motor cortex, providing evidence that a small electric field crosses the skull and influences the brain. A possible mechanism of action of scalp DC is the hyperpolarization of the superficial excitatory interneurones in the human motor cortex.

PMID: 9694210 [PubMed - indexed for MEDLINE]

Brain Research Bulletin. 2007 May 30;72(4-6):208-14

Safety aspects of transcranial direct current stimulation concerning healthy subjects and patients.

Poreisz C, Boros K, Antal A, Paulus W.

Department of Clinical Neurophysiology, Georg-August University, Robert Koch Strasse 40, 37075 Göttingen, Germany. csaba.poreisz@med.ni-goettingen.de

Cortical excitability changes induced by tDCS and revealed by TMS, are increasingly being used as an index of neuronal plasticity in the human cortex. The aim of this paper is to summarize the partially adverse effects of 567 tDCS sessions over motor and non-motor cortical areas (occipital, temporal, parietal)  from the last 2 years, on work performed in our laboratories. One-hundred and two of our subjects who participated in our tDCS studies completed a questionnaire. The questionnaire contained rating scales regarding the presence and severity of  headache, difficulties in concentrating, acute mood changes, visual perceptual changes and any discomforting sensation like pain, tingling, itching or burning under the electrodes, during and after tDCS. Participants were healthy subjects (75.5%), migraine patients (8.8%), post-stroke patients (5.9%) and tinnitus patients (9.8%). During tDCS a mild tingling sensation was the most common reported adverse effect (70.6%), moderate fatigue was felt by 35.3% of the subjects, whereas a light itching sensation under the stimulation electrodes occurred in 30.4% of cases. After tDCS headache (11.8%), nausea (2.9%) and insomnia (0.98%) were reported, but fairly infrequently. In addition, the incidence of the itching sensation (p=0.02) and the intensity of tingling sensation (p=0.02) were significantly higher during tDCS in the group of the healthy subjects, in comparison to patients; whereas the occurrence of headache was significantly higher in the patient group (p=0.03) after the stimulation. Our results suggest that tDCS applied to motor and non-motor areas according to the present tDCS safety guidelines, is associated with relatively minor adverse effects in healthy humans and patients with varying neurological disorders.

PMID: 17452283 [PubMed - indexed for MEDLINE]

 

European Journal of Neuroscience. 2008 Oct;28(8):1667-73.

Modulating activity in the motor cortex affects performance for the two hands differently depending upon which hemisphere is stimulated.

Vines BW, Nair D, Schlaug G.

Department of Neurology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02215, USA.

We modulated neural excitability in the human motor cortex to investigate behavioral effects for both hands. In a previous study, we showed that decreasing excitability in the dominant motor cortex led to a decline in performance for the contralateral hand and an improvement for the ipsilateral hand; increasing excitability produced the opposite effects. Research suggests that the ipsilateral effects were mediated by interhemispheric inhibition. Physiological evidence points to an asymmetry in interhemispheric inhibition between the primary motor cortices, with stronger inhibitory projections coming from the dominant motor cortex. In the present study, we examined whether there is a hemispheric asymmetry in the effects on performance when modulating excitability  in the motor cortex. Anodal and cathodaltranscranial direct current stimulation  were applied to the motor cortex of 17 participants, targeting the non-dominant hemisphere on one day and the dominant hemisphere on another day, along with one  sham session. Participants performed a finger-sequence coordination task with each hand before and after stimulation. The dependent variable was calculated as  the percentage of change in the number of correct keystrokes. We found that the effects of transcranial direct current stimulation depended upon which hemisphere was stimulated; modulating excitability in the dominant motor cortex significantly affected performance for the contralateral and ipsilateral hands, whereas modulating excitability in the non-dominant motor cortex only had a significant impact for the contralateral hand. These results provide evidence for a hemispheric asymmetry in the ipsilateral effects of modulating excitability in  the motor cortex and may be important for clinical research on motor recovery.

PMID: 18973584 [PubMed - in process]

 

BMC Neuroscieces. 2008 Oct 28;9:103.

Dual-hemisphere tDCS facilitates greater improvements for healthy subjects' non-dominant hand compared to uni-hemisphere stimulation.

Vines BW, Cerruti C, Schlaug G.

Department of Neurology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02215, USA. bradley.vines@gmail.com

BACKGROUND: Transcranial direct current stimulation (tDCS) is a non-invasive technique that has been found to modulate the excitability of neurons in the brain. The polarity of the current applied to the scalp determines the effects of tDCS on the underlying tissue: anodal tDCS increases excitability, whereas cathodal tDCS decreases excitability. Research has shown that applying anodal tDCS to the non-dominant motor cortex can improve motor performance for the non-dominant hand, presumably by means of changes in synaptic plasticity between  neurons. Our previous studies also suggest that applying cathodal tDCS over the dominant motor cortex can improve performance for the non-dominant hand; this effect may result from modulating inhibitory projections (interhemispheric inhibition) between the motor cortices of the two hemispheres. We hypothesized that stimultaneously applying cathodal tDCS over the dominant motor cortex and anodal tDCS over the non-dominant motor cortex would have a greater effect on finger sequence performance for the non-dominant hand, compared to stimulating only the non-dominant motor cortex. Sixteen right-handed participants underwent three stimulation conditions: 1) dual-hemisphere - with anodal tDCS over the non-dominant motor cortex, and cathodal tDCS over the dominant motor cortex, 2) uni-hemisphere - with anodal tDCS over the non-dominant motor cortex, and 3) sham tDCS. Participants performed a finger-sequencing task with the non-dominant hand  before and after each stimulation. The dependent variable was the percentage of change in performance, comparing pre- and post-tDCS scores. RESULTS: A repeated measures ANOVA yielded a significant effect of tDCS condition (F(2,30) = 4.468, p = .037). Post-hoc analyses revealed that dual-hemisphere stimulation improved performance significantly more than both uni-hemisphere (p = .021) and sham stimulation (p = .041). CONCLUSION: We propose that simultaneously applying cathodal tDCS over the dominant motor cortex and anodal tDCS over the non-dominant motor cortex produced an additive effect, which facilitated motor performance in the non-dominant hand. These findings are relevant to motor skill  learning and to research studies of motor recovery after stroke.

PMID: 18957075 [PubMed - in process]