Gamma is defined as a brain frequency ranging from about 25 Hz to 100 Hz or higher, though it is most strongly seen around 40 Hz. The discussion of Gamma and what it is and does has appeared fairly recently, since analog EEG readings don’t measure above 25 Hz. Even in the development of digital EEG, though Gamma had been identified in the 1960’s, the amplifiers used in recording EEG only registered into the low 30 Hz bands. As a result, Gamma is not included in most of the databases used today to determine what a “normal” EEG looks like.
What is Gamma
Gamma, like alpha, theta and delta—is a synchronous frequency. It is found in waking and dreaming states. It originates in rhythm generators in the thalamus and is modulated by the brainstem. It sweeps the brain from front to back about 40 times per second, causing the brain’s billions of cortical neurons to resonate together. It is theorized to allow them most efficiently to share information and combine their efforts. Thus it is seen as the basis of “consciousness”—the ability to integrate multiple sensory inputs, memories and feelings into a single unified awareness. It has been called the “binding” frequency. Damage to the thalamus which disrupts the brain’s ability to produce these gamma sweeps is reported to result in a deep coma state.
As critical as this ability to bring together distributed functions of brain areas into focused attention is, there is another area of gamma research relating to our ability to experience others outside ourselves.
Gamma in Meditation
Meditators have long been defined by their ability to produce synchronous 10 Hz alpha, the resting-ready brain state. However, since much of the early work with “peak” brains was done with amplifiers that did not record frequencies as high as 40 Hz, the gamma rhythm was not seen. Research in the early 2000’s with Tibetan monks demonstrated that synchronous gamma apparently also relates to transcendental experience.
When master meditators were asked to move into a state of “objective compassion”, their gamma levels surged as a result of highly synchronous activity. This did not appear in less experienced meditators (though they were able to increase it with practice.) Objective compassion is the ability to feel and resonate with the experience of another without needing to intervene. It involves recognizing and maintaining the “boundary” between ourselves and the object of our empathy. It might be thought of as the godlike type of love that feels our pain or joy without trying to impose its own “solutions”—letting us find our own way through our lives.
Brain frequencies, like musical frequencies when they are synchronous, tend to produce “harmonics” or overtones. For example, a strong 10 Hz alpha frequency tends to cause an increase at 20 Hz (beta) and a smaller one at 40 Hz. It has also been suggested that the gamma sweep relates to extremely slow frequencies produced in the brain stem.
High frequencies in the range of gamma can also result from so-called “muscle artifact”. We’ll talk more about that later, but tension in muscles near EEG electrodes can be picked up in the EEG and appear as brain activity. Obviously this is not real gamma.
We have discussed hibeta (23-38 Hz) frequencies previously. They are not desirable, since they often relate to anxiety. Gamma training often works with bands of 35-45 Hz or 38-42 Hz (centered around 40 Hz) as our target. In brains that are prone to making hibeta, this training may actually increase this undesirable activity.
The goal of gamma training is to increase synchronous gamma, It should not increase hibeta (which ordinarily is not synchronous). However, when we increase synchrony in a frequency, since the pulses of millions of neurons accur at the same time, the amplitude (or size) of the signal also tends to increase. Since it is much easier to measure the size of a signal than to measure its synchronicity, many systems attempt to train increased synchrony by training increased amplitude. Unfortunately, that’s not the only way to increase amplitude. It’s possible to increase levels of excitation in the fast frequencies without making them synchronous. When this happens, most often in the brains of people who tend toward bursts of hibeta, clients can experience increased anxiety or irritation—the exact opposite of their training goal.