Noninvasive brain stimulation uses gentle electrical currents applied to the scalp to reversibly modulate brain function. The little ‘t’ stands for transcranial, and the shape of the waveform determine how neural activity is modified. Learn the lingo below.
tDCS stands for transcranial direct current stimulation. Positive currents enter the head and negative currents leave the head.
tPCS stands for pulsed current stimulation. Currents in tPCS are brief but repeat over and over.
tACS stands for transcranial alternating current stimulation, where currents oscillate over time.
tIFS stands for transcranial interferential stimulation and is derived by combining two AC waves.
The materials that deliver the stimulation, such as stainless steel or carbon rubber. But don’t confuse the electrode with the sponge that is the interface placed between the electrode and scalp to reduce skin sensations.
Positive currents enhance brain activity. These currents are weak and don’t directly modulate the brain. Rather, they promote enhanced activity by increasing the probability of neural firing.
Negative currents counter and complement the positive currents. The negative electrode is called the cathode, which serves to calm or quiet brain activity.
Sinusoidal currents have a push (positive) and pull (negative). These currents help coordinate brain activity, so they act like a metronome to keep a rhythm or beat.