For a long time neuroscientists have shown work from poor unsuspecting birds and cats that there are specific critical periods in development important for a functional visual system or a species-appropriate bird song. In humans there have been a few unfortunate cases of horrific neglect of children (i.e. Genie) that have likely been responsible for profound intellectual deficits, which have been informative to scientists interested in the consequences of depravation during the early years. But scientists have not been able to conduct a formal and yet ethical scientific experiment to measure the relationship between a critical period and its function in humans until now, thanks to the ability to measure gamma.
On Oct 21st, the Science Daily featured an article on the exploration of the critical period for language development and other skills in toddlers by measuring their gamma waves on the EEG. The time period between 16 to 36 months is a time of tremendous language growth in humans, where their vocabulary typically expands from about 100 to 1000 words. Dr. April Benasich from Rutgers University in Newark, measured gamma activity in the frontal cortex of toddlers (16, 24 and 36 months) while they sat on a parent’s lap and quietly played. Gamma power (which is determined by the amount of synchronous gamma firing) was associated with language development, cognitive skills, behavior and impulse control. The more advanced a child’s language or cognitive skills, the more gamma power that child showed. And as expected, children who’s parents had a history of language impairments showed lower gamma power.
This new finding is consistent with what is already known about gamma in adults and from work in animals. Gamma heightens during the processing of linguistic information, during the formation of ideas and memories and during other abilities. Furthermore, gamma fires between 2 regions of the brain during associative learning, when a new concept is linked to one already known.
Low gamma coherence within different hemispheres is associated with ADD and learning disabilities. In fact Dr. C. Njiokiktjien from the Amsterdam, Netherlands compared intrahemispheric coherences of various frequencies (including gamma) of children with non-verbal vs. verbal learning disabilities(1). Their results suggested that children with non-verbal learning disabilities had less connectivity in the right hemisphere, which is consistent with the idea that it’s the right hemisphere that manages spatial skills, as well as other non-verbal tasks.
Dr. Hermann from Magdeburg University in Germany presents a model of gamma based on its power under various psychiatric conditions(2). Too much gamma firing is associated with ADHD, positive associations in Schizophrenia (i.e. hallucinations) and epilepsy, and Alzheimer’s disease, negative symptoms of Schizophrenia (i.e. blunt or flat affects) are associated with too little gamma.
So can we benefit from using brainwave entrainment to help us enter gamma states? Or are there risks associated with having more gamma power?
Dr. R. Olmstead, a clinical psychologist from Sunrise, FL, found benefits with gamma training in children with non-verbal learning disabilities, ages 6-16(3). She exposed them to 35 min brainwave entrainment sessions twice a week for 6 weeks. The sessions alternated between excitatory sessions (increasing from 14 (beta) to 40 (gamma) Hz), and inhibitory sessions (decreasing from 40 to 14 Hz). She found that her training enhanced various non-verbal cognitive abilities such as processing speed, freedom from distractibility, arithmetic and coding.
But what about the rest of us?
I think there is good reason to hypothesize that gamma training might also benefit many with other learning disabilities as well. But I am concerned about the fact that ADHD is associated with too much gamma firing. Thus if you have a learning disability and ADHD, or just ADHD alone, or even if you didn’t have any signs of ADHD, would gamma training enhance your distractibility or impulsiveness?
Unfortunately, there hasn’t been enough research done to answer these questions at this point. However, there is good news. Brainwave entrainment for most of the population is a very gentle stimulus, and it takes time for cognitive benefits to take effect. Thus training with gamma (or any other stimulus) is done slowly. All such training should be conducted mindfully, and if you start to develop any unwanted symptoms, you can simply stop your training, and the effects will likely to go away. The higher the gamma power, the more severe the symptoms, so ignoring milder unwanted side effects could be dangerous.
The study by Olmstead might also be a good example as to how to safely train gamma. She trained students to progress into gamma with the excitatory protocol, and to leave gamma and return to beta in the inhibitory protocol. I would imagine that such training is good for leading our brains in and out of gamma as needed. And thus it might be teaching our brains to self regulate.
Nevertheless, there is an element of adventure in using gamma to potentially enhance your cognitive skills, and if the idea makes you queasy, I’d stand back and wait for more research to be done.
1 Njiokiktjien C, de Rijke W, Jonkman EJ. Children with non-verbal learning disabilities (NLD): coherence values in the resting state may reflect hypofunctional long distance connections in the right hemisphere. Fiziologiia cheloveka. 2001; 27: 17-22.
2 Herrmann CS, Demiralp T. Human EEG gamma oscillations in neuropsychiatric disorders. Clin Neurophysiol. 2005; 116: 2719-33.
3 Olmstead R. Use of Auditory and Visual Stimulation to Improve Cognitive Abilities in Learning-Disabled Children. Journal of Neurotherapy. 2005; 9: 49-61.