Non-invasive brain stimulation techniques, such as tDCS are getting a lot of attention today. Effectiveness of this technique is comparable with standard brain stimulation methods, but the difference lies in much greater safety and wider range of applications. Transcranial DCS is based on low intensity electrical currents delivered to different parts of the brain depending on the disorder. The current is delivered using electrodes placed on the surface scalp, so there is no direct contact between the electrodes and the brain tissue. Here are some of the most important positive effects of tDCS.
Chronic Pain Management
Many studies proved the effectiveness of tDCS in chronic pain management. This is especially true for so called “neuropathic pain” caused by some neurological conditions, which does not respond to standard medication therapy. In one study, tDCS significantly decreased chronic neuropathic pain in patients with multiple sclerosis and improved their quality of life (Mori et al., 2010). Another randomized controlled trial assessed the effects of tDCS in patients who did or did not benefit from other types of brain stimulation (O’Neill, Sacco, & Nurmikko, 2015). They found tDCS to be effective even in some patients who did not respond to standard stimulation methods. Other studies also confirmed beneficial effects of tDCS on chronic pain management (Sakrajai et al., 2014; Zaghi, Heine, & Fregni, 2009).
Depression
Conventional treatment for depression currently includes several different types of antidepressant medications. Although they are effective, side effects are very common. Attempts to treat depression with tDCS were successful, which means that patients can now manage their depressive symptoms without experiencing side effects. In severe cases, antidepressants still need to be used, but their dosage can be lowered by addition of tDCS treatment. Many studies proved the effectiveness of tDCS for different types of depressive disorders (Berlim, Van den Eynde, & Daskalakis, 2013; Murphy, Boggio, & Fregni, 2009; Nitsche, Boggio, Fregni, & Pascual-Leone, 2009).
Cognitive Functions
Positive effects of tDCS on mood and cognitive functions have been noticed in both psychiatric patients and after neurological events, such as stroke. A case study showed great improvement in cognitive function in one patient accomplished by using tDCS anodal stimulation after stroke (Bueno, Brunoni, Boggio, Bensenor, & Fregni, 2011). In combination with cognitive training, tDCS can improve cognition and task-performing abilities even in healthy subjects (Martin, Liu, Alonzo, Green, & Loo, 2014). Current scientific literature reviews undoubtedly show that tDCS treatment leads to cognitive enhancement and memory improvement in both healthy subjects and patients with various disorders (Bennabi et al., 2014).
Motor Performance
Impaired motor performance is an important element of most neurological disorders and the main cause of disability in neurological patients. There are many methods, including surgery, medications, and electric stimulation techniques aimed to improve motor performance. Studies suggest that tDCS has promising future in this aspect too (Reis & Fritsch, 2011). Anodal stimulation of motor cortex affected by stroke significantly improved motor performance (Kim, Ohn, Yang, Park, & Jung, 2009). In healthy persons, exercising performance was improved and muscle fatigue was decreased using tDCS (Williams, Hoffman, & Clark, 2013).
Parkinson’s Disease
Parkinson’s disease is a complex, degenerative neurological disease affecting mostly older population. Degeneration of all aspects of neural functions, including cognition, memory, and motor functions is the main feature of this disease. Electrical stimulation of basal nuclei (brain parts located deeply into the brain) is already used in the treatment of Parkinson’s disease. Transcranial DCS offers more convenient and safe approach than conventional techniques. In one study, motor function in patients with Parkinson’s disease was improved using tDCS (Fregni et al., 2006). Other studies have also confirmed the positive effects of tDCS in patients with Parkinson’s disease (Kaski, Allum, Bronstein, & Dominguez, 2014; Leite, Goncalves, & Carvalho, 2014).
Long-term Effects of tDCS
Effects of tDCS can be seen immediately after the session or after few sessions, depending on the underlying disease. Long-term effects are also noted, which is rarely the case with other types of brain stimulation. In one study, tDCS was aimed to improve speaking function in patients who had stroke .(Vestito, Rosellini, Mantero, & Bandini, 2014). The treatment lasted for two weeks, and the improvement of symptoms was noticeable even after 21st week. Another study included elderly participants and assessed long-term effects of tDCS on their cognitive function and memory (Park, Seo, Kim, & Ko, 2014). The participants have reached significant improvement which lasted for 4 weeks after the treatment. Therefore, tDCS shows substantial long-term effects in patients with different disorders.
References
Bennabi, D., Pedron, S., Haffen, E., Monnin, J., Peterschmitt, Y., & Van Waes, V. (2014). Transcranial direct current stimulation for memory enhancement: from clinical research to animal models. Front Syst Neurosci, 8, 159. doi: 10.3389/fnsys.2014.00159
Berlim, M. T., Van den Eynde, F., & Daskalakis, Z. J. (2013). Clinical utility of transcranial direct current stimulation (tDCS) for treating major depression: a systematic review and meta-analysis of randomized, double-blind and sham-controlled trials. J Psychiatr Res, 47(1), 1-7. doi: 10.1016/j.jpsychires.2012.09.025
Bueno, V. F., Brunoni, A. R., Boggio, P. S., Bensenor, I. M., & Fregni, F. (2011). Mood and cognitive effects of transcranial direct current stimulation in post-stroke depression. Neurocase, 17(4), 318-322. doi: 10.1080/13554794.2010.509319
Fregni, F., Boggio, P. S., Santos, M. C., Lima, M., Vieira, A. L., Rigonatti, S. P., . . . Pascual-Leone, A. (2006). Noninvasive cortical stimulation with transcranial direct current stimulation in Parkinson’s disease. Mov Disord, 21(10), 1693-1702. doi: 10.1002/mds.21012
Kaski, D., Allum, J. H., Bronstein, A. M., & Dominguez, R. O. (2014). Applying anodal tDCS during tango dancing in a patient with Parkinson’s disease. Neurosci Lett, 568, 39-43. doi: 10.1016/j.neulet.2014.03.043
Kim, D. Y., Ohn, S. H., Yang, E. J., Park, C. I., & Jung, K. J. (2009). Enhancing motor performance by anodal transcranial direct current stimulation in subacute stroke patients. Am J Phys Med Rehabil, 88(10), 829-836. doi: 10.1097/PHM.0b013e3181b811e3
Leite, J., Goncalves, O. F., & Carvalho, S. (2014). Facilitative effects of bi-hemispheric tDCS in cognitive deficits of Parkinson disease patients. Med Hypotheses, 82(2), 138-140. doi: 10.1016/j.mehy.2013.11.021
Martin, D. M., Liu, R., Alonzo, A., Green, M., & Loo, C. K. (2014). Use of transcranial direct current stimulation (tDCS) to enhance cognitive training: effect of timing of stimulation. Exp Brain Res, 232(10), 3345-3351. doi: 10.1007/s00221-014-4022-x
Mori, F., Codeca, C., Kusayanagi, H., Monteleone, F., Buttari, F., Fiore, S., . . . Centonze, D. (2010). Effects of anodal transcranial direct current stimulation on chronic neuropathic pain in patients with multiple sclerosis. J Pain, 11(5), 436-442. doi: 10.1016/j.jpain.2009.08.011
Murphy, D. N., Boggio, P., & Fregni, F. (2009). Transcranial direct current stimulation as a therapeutic tool for the treatment of major depression: insights from past and recent clinical studies. Curr Opin Psychiatry, 22(3), 306-311. doi: 10.1097/YCO.0b013e32832a133f
Nitsche, M. A., Boggio, P. S., Fregni, F., & Pascual-Leone, A. (2009). Treatment of depression with transcranial direct current stimulation (tDCS): a review. Exp Neurol, 219(1), 14-19. doi: 10.1016/j.expneurol.2009.03.038
O’Neill, F., Sacco, P., & Nurmikko, T. (2015). Evaluation of a home-based transcranial direct current stimulation (tDCS) treatment device for chronic pain: study protocol for a randomised controlled trial. Trials, 16(1), 186. doi: 10.1186/s13063-015-0710-5
Park, S. H., Seo, J. H., Kim, Y. H., & Ko, M. H. (2014). Long-term effects of transcranial direct current stimulation combined with computer-assisted cognitive training in healthy older adults. Neuroreport, 25(2), 122-126. doi: 10.1097/WNR.0000000000000080
Reis, J., & Fritsch, B. (2011). Modulation of motor performance and motor learning by transcranial direct current stimulation. Curr Opin Neurol, 24(6), 590-596. doi: 10.1097/WCO.0b013e32834c3db0
Sakrajai, P., Janyacharoen, T., Jensen, M. P., Sawanyawisuth, K., Auvichayapat, N., Tunkamnerdthai, O., . . . Auvichayapat, P. (2014). Pain reduction in myofascial pain syndrome by anodal transcranial direct current stimulation combined with standard treatment: a randomized controlled study. Clin J Pain, 30(12), 1076-1083. doi: 10.1097/AJP.0000000000000069
Vestito, L., Rosellini, S., Mantero, M., & Bandini, F. (2014). Long-term effects of transcranial direct-current stimulation in chronic post-stroke aphasia: a pilot study. Front Hum Neurosci, 8, 785. doi: 10.3389/fnhum.2014.00785
Williams, P. S., Hoffman, R. L., & Clark, B. C. (2013). Preliminary Evidence That Anodal Transcranial Direct Current Stimulation Enhances Time to Task Failure of a Sustained Submaximal Contraction. PLoS ONE, 8(12), e81418. doi: 10.1371/journal.pone.0081418
Zaghi, S., Heine, N., & Fregni, F. (2009). Brain stimulation for the treatment of pain: A review of costs, clinical effects, and mechanisms of treatment for three different central neuromodulatory approaches. J Pain Manag, 2(3), 339-352.