tDCS: transcranial Direct Current Stimulation

About tDCS

tDCS as we know it today was invented by Michael Nitsche, a German scientist in 2001 (not pictured).

Nitsche wondered what effect electrical current would have on the brain?

Brain activity is electrical signals between neurons, so what effect would an alien electrical current have on that activity?

To find out, Nitsche conducted the first tDCS experiments on himself. As you do :)


focus ohms law

The technology required to make a tDCS stimulator is surprisingly simple.

It is governed by Ohms law which states Voltage(V) = current (I) * Resistance(R) So to achieve the desired fixed current (I), the voltage divided by resistance should equal 2mA

Complication arise because the circuit is passing through electronic components and biological matter e.g. your head. The human head does not provide a fixed resistance. Blood flow in the skin and brain, together with changes to chemical composition means the resistance is in constant flux. The goal is to have a fixed output current a good stimulator must constantly measure the resistance and adjust the voltage to balance the output.

In those first studies currents of 1mA for durations of 1 minute were tested.


focus tdcs brain functions

But how to test the tDCS theory?

Science has largely established which areas of the brain are responsible for which broad function.

The pre-frontal cortex at the front of the head is responsible for higher intellect and self control.

The occipital lobe is responsible for vision.

Across the middle of the brain the motor cortex controls our movement, including fine motor control of hands and fingers.

So the tDCS experiments looked to pass a current through a particular region and then test how that function of the brain changed.

The theory was that if the stimulation is doing something it should be possible to measure a difference before and after the stimulation.

The tDCS test results?

Well the first studies were small in size, often with just a handful of test subjects.

But there did appear to be some interesting data in the results. It appeared that the region of the brain stimulated performed its usual tasks “better” with stimulation. The difference was small, but it was a statistically significant difference in the stimulated participants.

It was also noted that the direction of current flow had a major impact. Just as it was possible to improve a function, it was also possible to impair it. Sending a current in the reverse direction had the opposite effect.

As no negative short-term side effects were noticed, this led to trials with higher current levels 2mA and longer durations, up to 30 minutes. Safety protocols were established from the early trials. The papers Nitsche published had a large impact. Encouraged other neuroscientists to see how tDCS could affect their area of expertise. Soon papers were being published from Universities all around the world. Just about every region of the brain was stimulated and measured.



New Scientist - Zap your brain into the zone

Zen and the art of genius (Image: The Red Dress)

As with many scientific discoveries, it didn’t take long for the military to take an interest in tDCS.

The US military agency DARPA funded some studies in New Mexico. The results were staggering. Soldiers acquired new skills at double the normal rate with stimulation.

Aside: Sally Adees article in New Scientist about the Darpa study led to the creation of foc.us

focus tdcs, not magic

But tDCS is not magic.

By itself it won’t make you smarter, fitter or know something you don’t.

What it will do, is get you ready to learn, train or discover yourself.

The soldiers in the DARPA study still had to practice and learn, they just learnt faster with tDCS.

tDCS will not give you abs like this