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What Effect Does Gamma Brainwave Enhancement Have?

Initial research is promising but we need human studies on brain injury.

John Hain/Pixabay
Source: John Hain/Pixabay

In 2012, I approached Dr. Lynda Thompson of the ADD Centre in Toronto about conducting a single-subject research study on me to investigate the effect of gamma brainwave biofeedback. I approached her because of her past success in treating my brain injury and because of the significant effects of time-limited continuous-release pregabalin on my emotions, neurophysiologically-based anxiety, fatigue, exercise tolerance, and several other brain functions. I wanted to increase GABA (gamma-Aminobutyric acid) to achieve these effects permanently without the unwanted side effects of controlled-release pregabalin.

Thompson and the ADD Centre assessed me to first determine if I had low gamma brainwave activity. Since I did, they designed a protocol of single-electrode brain biofeedback at CZ, to be conducted twice a week. I detailed the study in my memoir, Concussion Is Brain Injury: Treating the Neurons and Me, and began the hypothesis section as follows:

“Brain biofeedback stimulates neural networks thereby increasing brainwave power at chosen frequencies in different parts of the brain in order to repair and normalize brain functions. In discussions with Dr. Lynda Thompson of the ADD Centre, we hypothesized brain biofeedback to stimulate the networks that produce gamma brainwaves would both enhance gamma activity and increase release of GABA between the related neurons and thus reproduce the effects I had experienced [with pregabalin].”

The results were quick to see and dramatic, chief among them being the neurostimulation treatment’s immediate de-stressing effect and sudden increase in my intellectual capacity. When brain biofeedback training increased gamma brainwave activity, all the other desired brainwave frequencies increased as well, including alpha, like a supporting wave lifting a boat and powering it forward.

I partly explained its de-stressing effect this way:

“When your emotions work well, when your thoughts are clear, when your perceptions both sensory and mentally are freer flowing, it is much easier to perceive the problem, understand the problem, process the problem, and have emotions to guide cognitions to resolve the problem. That increases a sense of competence and drops worry.”

The chief contraindication for gamma brainwave biofeedback is too-high muscle tension. Because gamma brainwaves have small wave amplitudes, EMG—that is, muscle artifact—can easily swamp it, leading to training EMG instead of gamma. According to Thompson, “One has to be very strict about reducing muscle artifact whenever one works with EEG.” Thus, the clients must be able to keep EMG below 2 μV.

Few are able to achieve that.

I hypothesized that using passive audiovisual entrainment stimulation of gamma would overcome this problem. In 2020, I was able to test this hypothesis after Mind Alive added three different gamma brainwave sessions onto two of its devices. Again, gamma training—in this case passive entrainment—significantly reduced anxiety as well as the vigilance brought on by the pandemic. It also reduced my fatigue and allowed me to practice reading consistently, among other benefits, which I tracked.

Investigations of both of these methods of gamma brainwave training on humans are limited. And researchers seem to focus more on Alzheimer’s Disease and mouse studies. As I wrote on my brain injury website explaining the neurophysiological changes in brain injury, microglia "eat proteins that if left to accumulate would lead to the plaques of Alzheimers.” Nature neuroscience visualized this process.

Yet if we treated brain injury, we may prevent dementia; thus researchers putting their focus on one of the causations—brain injury, instead of the result—Alzheimer’s Disease, could reap bigger rewards.

The mouse studies demonstrated the neurophysiological changes that can explain the changes I saw in me. In 2016, HF Iaccarino et al reported that “a non-invasive 40 Hz [gamma] light-flickering regime that reduced Aβ1-40 and Aβ1-42 levels in the visual cortex of pre-depositing mice and mitigated plaque load in aged, depositing mice [uncovered] a previously unappreciated function of gamma rhythms in recruiting both neuronal and glial responses to attenuate Alzheimer's-disease-associated pathology.”

But mouse studies don’t always translate to humans.

In 2022, Elvira Khachatryan et al studied “Gamma ENtrainment Using Sensory stimulation (GENUS)” on 16 participants, 15 with Alzheimer’s Disease (AD) and one with epilepsy. They included a cognitive task, and the combination led to:

“...a positive effect on the strength and extent of the gamma entrainment [and promoted] the propagation of gamma entrainment to additional neural areas including deep ones such as hippocampus which were not recruited when no cognitive task was required from the participants. The latter is of particular interest given that the hippocampal complex is considered to be one of the primary targets for AD therapies.”

In The Angel and the Assassin, Donna Jackson Nakazawa wrote that after brain injury, microglia change to eat synapses and will communicate to microglia in healthy areas to stop their normal supportive function and eat synapses instead as well. But neurostimulation therapy resets microglia to return to supporting, maintaining, and growing neurons and neural pathways. Khachatryan et al’s study findings that neurostimulation effects reset the microglia and propagate through the brain fall in line with what Nakazawa reported. The results of my gamma training align with the results of Khachatryan et al’s—that engaging in a task that you desire to improve enhances treatment, whichever neurostimulation or neuromodulation method you use. However, I learnt from brain biofeedback training that it’s more efficacious to use a range rather than a single-frequency stimulus. And so I used the 38-to-42 Hz gamma audiovisual entrainment session as it was closest to my ADD Centre training sessions of enhancing 39 to 42 Hz brainwaves.

Mouse studies are useful in learning the exact mechanisms of gamma brainwave entrainment. But what we need now, in the face of rapidly increasing long COVID rates and potentially more dementia down the road, is human studies of people with brain injury using brain biofeedback and entrainment to enhance gamma brainwaves.

Copyright ©2022 Shireen Anne Jeejeebhoy


Iaccarino HF, Singer AC, Martorell AJ, Rudenko A, Gao F, Gillingham TZ, Mathys H, Seo J, Kritskiy O, Abdurrob F, Adaikkan C, Canter RG, Rueda R, Brown EN, Boyden ES, Tsai LH. Gamma frequency entrainment attenuates amyloid load and modifies microglia. Nature. 2016 Dec 7;540(7632):230-235. doi: 10.1038/nature20587. Erratum in: Nature. 2018 Oct;562(7725):E1. PMID: 27929004; PMCID: PMC5656389.

Khachatryan, E., Wittevrongel, B., Reinartz, M., Dauwe, I., Carrette, E., Meurs, A., Van Roost, D., Boon, P., & Van Hulle, M. M. (2022). Cognitive tasks propagate the neural entrainment in response to a visual 40 Hz stimulation in humans. Frontiers in aging neuroscience, 14, 1010765.

Nakazawa, Donna. (2020). The Angel and the Assassin: The Tiny Brain Cell that Changed the Course of Medicine. Random House/Ballantine.

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