Forum for Applied
Neurotechnology

Transcranial Electrical Stimulation

tES is a non-invasive procedure that applies weak electrical current through electrodes placed on the scalp to influence brain activity. Two main tES methods include transcranial Direct Current Stimulation (tDCS) and transcranial Alternating Current Stimulation (tACS). tES methods can be both applied as a stand-alone treatment or combined with other therapeutic interventions.

Transcranial Direct Current Stimulation

Transcranial Direct Current Stimulation (tDCS) is one of the most commonly used non-invasive brain stimulation technique that delivers a very low intensity, safe electrical current with neuromodulatory properties. The University Medical Center Göttingen has been one of the key centers in researching and developing this method.

How Does It Work?

Through electrodes placed on the scalp, the tDCS electrical currents modulate the brain excitability by subtly prompting the electrical balance of neurons making them more or less likely to activate rather than activating them directly.

Treatment Indications

tDCS offers a promising approach against post-stroke motor deficits, amyotrophic lateral sclerosis, major depressive disorder, cognitive impairments, chronic fatigue, Parkinson's Disease, attention-deficit/hyperactivity disorder as well as addiction, among others. this method.

Benefits

Potential benefits of tDCS include incremental improvements in mood, reductions in pain perception, and enhanced motor function or cognitive performance. Repeated application of tDCS can alter brain function at the network level, offering a non-invasive way to support rehabilitation

Potential Side Effects

tDCS is generally well tolerated, with adverse effects being mild and transient. Rare complications, such as marked typically result from improper execution or protocols. Clinician oversight, adherence to recommended parameters, and patient care help ensure patient comfort and safety.

Transcranial Alternating Current Stimulation

Pioneered by Andrea Antal in Göttingen, tACS is a method for influencing oscillatory brain activity. The alternating current aims to interact with the brain’s natural electrical rhythms (often called brainwaves).

How Does It Work?

tACS delivers a low-intensity, oscillating electrical current through electrodes placed on the scalp. Instead of a constant current, it delivers a rhythmic, wave-like electrical current. 

Treatment Indications

Because many symptoms and functions—like sleep, focus, emotion regulation,
or movement—are linked to specific rhythms, tACS can be used to support them. 

Benefits

Potential benefits of tACS include modulation of abnormal brain rhythms, improved cognitive performance, and symptom reduction in many neurological and psychiatric disorders. tACS offers a promising alternative or adjunct to medication.

Potential Side Effects

tACS is generally considered safe, with side effects usually mild and transient. Common effects include tingling or itching sensations under the electrodes. Serious adverse effects are rare when safety guidelines are followed.

Transcranial Auricular Vagus Nerve Stimulation

tVNS is a non-invasive method in which gentle electrical impulses are delivered through the skin of the outer ear to stimulate the vagus nerve, thereby influencing brain function and the body’s relaxation response. The tVNS E is currently the only transcutaneous, non-invasive vagus nerve stimulation device approved in Europe under the MDR (EU 2017/745).

How Does It Work?

Put simply, the vagus nerve connects the brain with the internal organs and regulates rest and recovery. Using ear clips placed on the outer ear, gentle impulses are transmitted to nerve endings close to the skin, which send relaxation signals to the brainstem. These signals support, among other things, a slowing of the heart rate, a reduction of inflammation, and the release of beneficial neurotransmitters.

Treatment Indications

tVNS calms overactive nerves and is approved for epilepsy, chronic migraine, depression, and Prader–Willi syndrome. Studies additionally show—often a reduction of ≥50% in epileptic seizures—as well as improvements in depression, anxiety, and chronic pain. Further potential applications include, among others, Crohn’s disease, stroke rehabilitation, tinnitus, sleep disorders, and irritable bowel syndrome.

Benefits

Potential benefits of tVNS include a reduction in the symptoms of neurological diseases associated with sympathovagal imbalance. It can reduce stress and promote relaxation while enhancing alertness, energy, and concentration. It may also improve well-being and have positive effects on attention and mental clarity, supporting performance in demanding situations.

 
 

Potential Side Effects

Side effects of tVNS are generally mild and transient (e.g., tingling, itching, or redness at the ear). When used correctly, serious adverse effects are rare, and studies confirm a high level of safety.