What is tDCS?
TDCS stands for Transcranial Direct Current Stimulation and is a form of neurostimulation (also known as neuromodulation) where very low levels of constant current are delivered to specifically targeted areas of the brain, often producing profound results. It was originally developed to help patients with brain injuries such as strokes, however tests on healthy adults demonstrated that tDCS can increase cognitive performance on a variety of tasks, depending on the area of the brain being stimulated. Scientific studies have shown that tDCS has the ability to enhance language and mathematical ability, attention span, problem solving, memory, and coordination. In addition, tDCS has also been documented as having impressive potential to treat depression, anxiety, PTSD, as well as chronic pain.
The Human BrainTo really understand tDCS, you must understand the human brain. The brain is the most complex organ in the human body, comprised of an intricate network of BILLIONS of nerve cells, called neurons. These special cells control and react to everything that happens in our bodies. The neurons in your brain communicate to each other using tiny electrical, and chemical impulses called synapses. Electrical synapses, unlike chemical synapses, conduct nerve impulses faster (approximately 10 times faster), causing vital information to pass from neuron to neuron more quickly.
How long do effects from tDCS last? The immediate effects usually last anywhere from 5 to 90 minutes after the end of the stimulation session. Some research has shown that repetitive stimulation, for example on a daily basis for one week, can educe longer lasting, and more “ingrained” effects. Additionally, a study on depression found that the beneficial effects of tDCS stimulation were shown to be apparent an entire month after the treatment. Furthermore, one study (considered anecdotal, not yet confirmed) recorded a lasting cognitive enhancement effect resulting from Transcranial Direct Current Stimulation ONE YEAR after the initial stimulation study.
How do I know where to position the electrodes? The great thing about tDCS is that there’s not just one placement! Research has shown that tDCS can produce a variety of affect depending on what areas of the brain are stimulated. To learn more about the different positions, you should familiarize yourself with positioning codes. As you begin researching different montages (aka electrode placements), it will help to refer to the 10-20 chart to understand what locations the author is discussing. While it is easy to visually estimate electrode placement based on the International 10-20 System, or by using online tDCS montage guides, precise positioning is recommended. Precise positioning involves measuring distances on your head using anatomical landmarks. A good guide on this can be found here. It’s also good to familiarize yourself with the names and basic functions of the various cortexes of the brain. The more you know, the more you grow!
What are montages and protocols?
For a complete list of tDCS terminology, see tDCS terms & definitions. Montages are the many different possible tDCS positions of both the anode and cathode electrodes on the body. The Protocol is actually a combination of the tDCS montage (electrode position) being used, the current level being used, and the total duration of the session. The most officially researched protocol is anodal (positiv me: red) stimulation of the left dorsolateral prefrontal cortex (L-DLPFC – F3), and cathode (negative: black) positioned on right Frontopolor (Fp2), located on the forehead above the right eyebrow, using 1mA of current for 20 minutes. This montage has been shown to improve many cognitive functions such as working memory, impulse control, reasoning, and learning.
What are some montages and their uses? There are many websites which provide information on tDCS montages, electrode placement instructions, and types of effects to be expected. Below are a few of the most reliable websites currently providing tDCS electrode montage placement information. In particular, Total tDCS has 3D graphics which makes estimating electrode placement much easier.