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Transcranial Direct-Current Stimulation (tDCS) is a brain stimulation technique that delivers a low electric current to the scalp. It is a non-invasive and painless procedure that helps in stimulating a specific brain part.
This neuromodulation brain stimulation technique uses a steady current between 1 – 2 mA delivered through electrodes to target the brain regions to modulate brain function. tDCS uses different electrode configurations to either excite or inhibit neuronal activity in the brain.
In the tDCS process, two electrodes are placed over the head and a low-intensity current is passed through. This brain stimulation technique modulates neuronal activity. There are two types of stimulation with tDCS –
Though tDCS is a brain stimulation procedure, it potentially has several advantages and can bring lasting changes in brain function almost immediately. The most common side effect of tDCS is slight itching or tingling on the scalp which usually is just a sensation and does not cause any pain or harm to neither the skin nor the brain.
The tDCS device is a small electronic device used to apply small levels of direct current (DC) to the brain. The tDCS procedure is easy to administer. The device usually has only two buttons – one to set the time duration and the other to set the current. The Anode electrode and the Cathode electrode are connected to the device with a cable. The current passes from the anode electrode to the brain and returns through the cathode electrode back to the device.
This treatment is particularly useful to improve language and mathematical ability, attention span, problem-solving, memory, and coordination.
Major Depressive Disorder
It has been found that, in depression, there is a lack of activity in the connections between certain areas of the cortex, the limbic system, and the dorsal and ventral neural system. The impairment in the activity of dorsal and ventral systems can also lead to weakened attention and other negative emotional responses. By performing transcranial direct current stimulation or tDCS with the application of the electrodes over the dorsal area, the activity of the left area can be improved, which can improve the working memory functions and the response rates in depressive disorders.
For the treatment of Obsessive-Compulsive Disorder or OCD, tDCS can be given along with cognitive-behavioral therapy and medications. tDCS works effectively to correct the imbalance in the CSTC (cortico-striatal-thalamo-cortical) pathway which controls movement execution, habit formation, and reward. Therefore, the procedure can act as a better alternative to deep cranial stimulation that is applied in refractory cases.
tDCS can show promising results in the treatment and management of dependency in the users of nicotine, cannabis, cocaine, alcohol, and other chemical substances. The dorsolateral prefrontal cortex is an essential brain structure for the regulation of craving behavior. Thus, prefrontal transcranial stimulation methods may be effective in reducing the chances of relapse and help bring a better perception to the quality of life.
tDCS has produced effective results in improving working memory and other cognitive functions which have been declined due to conditions like Alzheimer’s disease. The positive effects can be seen in a few sessions of direct cranial stimulation.
With active tDCS, patients have shown a significant reduction in their depressive symptoms in bipolar disorder within a few days of the treatment. Besides, the effects are long lasting even after the therapy sessions.
Schizophrenia presents many symptoms like hallucinations, abnormal movements, aberrant thinking, emotional blunting, social withdrawal, etc. The application of tDCS can increase cognitive abilities in individuals with schizophrenia, especially concerning working memory and attention. The electrodes are placed over the left temporoparietal junction and the left or right prefrontal area to reduce the symptoms.
Although the clinical trials and evidence suggest that the tDCS can be applied in numerous mental and cognitive disorders, the efficacy of the procedure has to be backed up by more data from further investigations. Moreover, additional studies are necessary to indicate the optimum dosage, right placement of electrodes, and the number of sessions required for the treatment of a particular condition.