tACS, transcranial alternating current stimulation, involves using two or more electrodes to send sinusoidal waveforms of electricity onto certain positions of the skull in the hopes that the energy goes into the brain and changes brain function.

Each tACS frequency is like a different substance, some frequencies need to be combined to get the right effects. Read this post to learn more about the benefits (and some drawbacks) of tACS.

tACS Brain Stimulation

EEGs (electroencephalography; brain voltage readers) commonly use a Fourier Transformation to convert linear-time sequences of voltage changes in the brain to the domain of frequencies. This is where we get alpha (8-12.5 Hz) for drowsiness, beta (12.5-30 Hz) for alertness, theta (4-7 Hz) for early NREM sleep and delta (0.1-3 Hz) for deep NREM sleep.

Theta and delta brainwaves are increased by alcohol [R].

Beta brainwaves are increased by LSD, mescaline, and psilocybin [R].

Thus, the legality and culture of substance use might change because of the brainwave model of cognitive function.

In the human brain, there are frequency bands that correspond to ultradian rhythm, a cycle of states of consciousness each with dominant brainwaves. The brainwaves cycle from rest to rest every 100 minutes (with activity between) and cycle from wakefulness to wakefulness every three to eight hours (with drowsiness between) [R].

Perhaps recording and analyzing our own brain signals can lead to scheduling our work life on cycles of states of consciousness. This may allow us to work harder in wakeful activity states and take short breaks in resting states and long breaks in resting drowsy states.


Health Benefits of tACS

1) tACS Improves Memory


Using theta waves on the left parietal area, tACS increases working memory as well as factual memory (or declarative), as found in 12 ADHD children (DB-RCT) [R, R, R, R].

Although, this only works when the theta waves are synchronized (phase-locked) [R, R].

Perhaps tACS increases memory confidence, as found in 12 healthy female humans [R].

Some want to use this for people with ADHD to get rid of memory loss, so ADHD children do better in school [R].

2) tACS Improves Learning

Using 6 Hz waves on the frontal cortex in 50 healthy human adults, tACS improved learning rate (DB-RCT) [R].

While with the same frequency on the temporoparietal cortex, tACS improved learning new words for 12 older adults [R].

3) tACS Improves Intelligence

With theta waves applied to the left parietal area, tACS improved intelligence to solve new problems, as found with 28 right-handed humans [R].

4) tACS Improves Reasoning

With gamma waves on the left middle frontal gyrus, tACS improved abstract reasoning and logical reasoning, found on 20 right-handed humans [R].

5) tACS Improves Reaction Times

Using 10 Hz on the primary motor cortex in 15 healthy humans, tACS improved reaction time [R].

Using 40 Hz on the right parietal lobe in 23 healthy right-handed young adults, tACS improved conscious reaction time [R].

6) tACS Changes Brainwaves

As found in 3 different studies on humans, tACS significantly increased brainwave power for 30 minutes in the wavelength range used to stimulate the brain after 20 minutes of stimulation [R, R, R].

With alpha waves (10 Hz), however, it only worked with eyes closed [R].

7) tACS Improves Neurochemistry

With square waves of 100 Hz put through the earlobes, tACS according to a review increased serotonin, beta-endorphin, ACTH, GABA, DHEA, and decreased tryptophan and cortisol in the blood after 20 minutes of stimulation [R].

So tACS might help insomnia and help depression [R].

Noradrenaline is also reduced by 200 Hz in rats [R].

When 15 and 500 Hz were used in 13 humans, it changed the same neurochemistry corresponding to improvements in symptoms of pain, insomnia, spasticity, depression and headache [R].

8) tACS May Suppress Tremors

In only 30 seconds with a phase-locking feature, tACS stopped tremors in 12 patients with Parkinson’s; the average patient had a 50% reduction in tremor strength [R].

9) tACS Improves Vision


tACS improved contrast detection, as found in 12 healthy humans at 60 Hz on the visual cortex [R].

tACS improved object detection on the parieto occipital cortex at 10 Hz, as found in 14 humans [R].

Gamma range tACS improves vertical motion detection if it’s placed in the right area according to a test with 45 healthy humans [R].

10) tACS Improves Movement

Gamma tACS improved movement, but beta tACS worsened movement, says a study on 18 humans [R].

With 50 Hz, tACS improved motor function, says a study with 15 healthy right-handers (DB-RCT) [R].

tACS also increased hand-eye coordination at 80 Hz according to a study with 14 humans [R].

11) tACS May Kill Tumors

Also, tACS allowed brain tumor patients to live twice as long (median) in a pilot clinical trial on 10 humans [R].

12) tACS Increases Strength


tACS significantly increased muscle power per distance (force per second) when used at 70 Hz, as found in 18 healthy subjects [R].

A beautiful woman manikin with EEG hat

13) tACS Treats Schizophrenia

With 0.5 Hz and 100 Hz put through the earlobes, tACS helped patients with schizophrenia to have significantly less aggression. They also needed less medication and were restrained less, in a study performed on nine people [R].

Some want to use this online for schizophrenia treatment [R].

Also, with 4.5 Hz on the dorsolateral prefrontal cortex, tACS improved negative symptoms of schizophrenia in three patients [R].

14) tACS Improves Anxiety


Found in a study on 12 patients, at 0.5 Hz and 0.3mA, tACS lowered anxiety in generalized anxiety disorder [R].

15) tACS Improves Visualization

At 8-11 Hz, tACS prolongs alpha waves, as shown in 23 humans. Prolonged alpha waves were associated with continued increase in visualization performance [R].

16) tACS Reduces Pain


In a study on 30 patients with spinal cord injury, with a 50 Hz signal, tACS significantly reduced pain [R].

It was shown that 4 Hz produced pain relief through the mu opioid receptors (acute/cannabidiol and morphine) and 100 Hz produced pain relief through the delta opioid receptor (chronic/cannabidiol) over three animal studies [R, R, R, R, R, R].

At 4 Hz and 100 Hz, tACS in mice reduced pain through alpha 2A adrenaline receptors (the type of pain ignored in fight or flight mode) [R].

17) tACS Improves Hearing


In a study on nine humans, using 35 Hz on the dorsolateral prefrontal cortex, tACS improved pitch memory [R].

tACS improved hearing the frequency used for stimulation, or so a study with 14 paid humans suggests [R].

As found by a study on 21 healthy humans using 40 Hz on the temples, tACS improved speech perception, thus having a potential for helping dyslexics and learning a new language [R].

18) tACS Helps Withdrawal

In 21 patients that were on a five-day washout from benzodiazepines, with a signal of 350 Hz, tACS significantly reduced anxiety and insomnia (DB-RCT) [R].

19) tACS Helps Recovering Alcoholics


In 20 patients that were abstinent for around three weeks, with 70-80 Hz square wave pulses, tACS increased MAO-B and GABA, thus increasing resistance to stress and anxiety (DB-RCT) [R, R, R].

20) tACS Induces Lucid Dreams

At 25 and 40 Hz of tACS stimulation in 27 healthy humans, 58% and 77% of the time, patients were sent into a lucid dream [R].

tACS Combined tDCS

Using tDCS of 1mA combined with tACS 0.425 mA of 10 Hz on 20 healthy right-handed humans, the phase of the electricity altered ability to detect sound with a reference phase [R].

Perhaps this will help in making a device that cancels out surrounding hums, and artificial silence.

tACS significantly lowers alpha waves (drowsiness) in the occipital lobe (vision) when placed on the forehead (cathode) and behind the ears (anode) at 70-80 Hz pulsed square waves, found in 20 humans (DB-RCT) [R].

Portrait of young man with EEG (electroencephalography) headset on head. Isolated on white background.

Health Risks of tACS

tACS Slows Movement

Both 10Hz and 20Hz on the left primary motor cortex with tACS significantly slowed finger tapping in a study on 15 humans; 10 Hz took 30 minutes to slow it significantly, and 20 Hz slowed it immediately (DB-RCT) [R].

tACS May Be Painful

Some patients got red and dry skin after using tACS [R].

Some patients also get vertigo, nausea, anger, a metallic taste, a heavy feeling, or intense ear ringing, although 94% felt no negative side effects [R].

So far, no one has experienced memory loss; tACS can’t help hypnotism [R].

tACS May Trigger Tingle Feeling (Pins and Needles)

With alpha and high gamma frequency ranges, tACS creates a sensation of pins and needles, a tingling without pain [R].

tACS May Trigger Flashing Light (Phosphenes)

Seeing phosphenes means seeing light without any light entering your eye; a hallucination.

When in a light room, tACS triggers flickering light with stimulation in the beta range.

Although in a dark room, tACS triggers flickering light with stimulation in the alpha range [R].

tACS May Make You a Risk Taker

With theta waves on the left dorsolateral prefrontal cortex, tACS increases riskier decision-making [R].

This was a study on 27 healthy humans (DB-RCT).

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