tCS – Transcranial Stimulation (aka) tES – Transcranial Electrical Stimulation
The acronyms tCS and tES (often used interchangeably) are used to describe any therapy in which electricity is applied on or through the cranium. In comparison to all of the types of cranial stimulation listed below, it is generally understood by most that tDCS is safer, more comfortable, easier to engage in, more affordable, and will often produce a more robust response. However it is important to note that new theories and opinions on the different forms of tCS/tES are being developed on an ongoing basis.
tACS – Transcranial Alternating Current Stimulation
During tACS, very low levels of alternating current are applied to the brain, usually via a set of non-invasive electrodes placed on the head. Alternating current is different from direct current in that electrical current periodically reverses direction, taking the graphical form of a sinusoidal shape. Amplitude, frequency and relative phases across stimulation electrodes can be controlled. tACS and it’s effect on the brain is currently the subject of an active research field in basic and clinical Neuroscience.
tRNS – Transcranial Random Noise Stimulation
A new form of transcranial electrical stimulation, first tested in 2008 at a public research University in Göttingen, Germany. Like tACS, tRNS uses oscillating current, with the distinction being tRNS utilizes random amplitude and frequency. While this stimulation method is still very new, it is hypothesized that tRNS’s effects are mainly excitatory, and that higher frequencies may produce greater results.
TENS – Transcutaneous Electrical Nerve Stimulation
Usually used in muscle therapy and not intended for use on the cranium. Transcutaneous is defined as existing, applied, or measure across the depth of the skin.
CES – Cranial Electrotherapy Stimulation
Applies a small, pulsed (AC) electric current across a patient’s head to treat anxiety, depression, insomnia and chronic pain. The term CES is often used interchangeably with tACS to refer to the same type of device.
TMS – Transcranial Magnetic Stimulation
Utilizes magnetic fields to stimulate nerve cells in the brain, and is usually used to treat depression in patients where other therapies have proven ineffective. TMS can be very particular and should only be performed by a qualified technician. To learn more about TMS and rTMS (Repetitive Transcranial Magnetic Stimulation), see our Brain Stimulation Comparison page.
ECT – Electroconvulsive therapy, or “shock therapy”
Made familiar to the public through a scene in the 1975 film, One Flew Over the Cuckoo’s Nest. ECT utilizes a current incredibly larger than most forms of cranial electrical stimulation (around 600-1000 milliamps), and is applied to the entire brain, often via the temples. This form of therapy usually results in a controlled grand mal seizure and must be done under general anesthesia. Because ECT produces significant side effects, including memory loss and confusion, it is only used for patients with severe, treatment-resistant depression, and even then it is used as a last result measure. To learn more about ECT, see our Brain Stimulation Comparison page.
Brain Stimulation Techniques Graphical Comparison
A fantastic comparison of tDCS, tACS, tRNS, and tACS from the July 2014 book, The Stimulated Brain – Cognitive Enhancement Using Non-Invasive Brain Stimulation (Page 38, Figure 2.1) edited by Roi Cohen Kadosh.