Depending on what we are thinking, how hard we are concentrating, our brain chemistry, environment, and a number of other factors, our brains have a certain electromagnetic signature, a wave frequency, which we can measure with available technology, namely electroencephalographs (EEG). Traditionally, these continuous rhythmic sinusoidal EEG waves were classified into four types: delta, theta, alpha and beta waves. Delta had a frequency range up to 4 Hz, associated with infants and children. Theta ranged from 4-8 Hz, and was linked with adolescence, trance and the preconscious state just before waking. Alpha (Berger’s) waves, 8-12 HZ, were tied to relaxed, alert consciousness. While, Beta waves, 12 Hz and above, were related to anxious thinking and active concentration. However, as increasing evidence for higher frequency brain activity came to light, Gamma waves lay claim the 26-80 Hz range, known euphemistically as “coherent 40 Hz oscillations.” These waves seem to go together with higher mental processes, perception and consciousness, making them the brain waves you probably want to have.
Gamma waves do not result from axonal-dendritic synapses, but rather from dentro-dendritic gap junctions that form after a synapse activation that links neurons together. Neurons connected by gap junctions have one common membrane, fire simultaneously and generally behave like a single giant neuron. These mega-neurons have membranes that depolarize coherently and can spread across different parts of the cortex (potentially allowing for brain-wide states). Normally, these networks are transient, as gap junctions form and dissolve constantly. But, recent research showing that practiced meditators like Tibetan monks can muscle 25-42 Hz easy, with some pushing 80-120 Hz, suggests that it is possible to keep the gap junctions open longer.
The relation between meditation and high wave frequency is not surprising, since the middle frequency (12-16 Hz), the sensorimotor rhythm, goes together with physical stillness. Just sitting still for a while is already half-way to Gamma. From there on, it almost seems it is just a matter of how much of your brain you have under control. Heightened consciousness, known as Samadhi in the meditation traditions, is an experience unclouded by cognitive contents. One usually arrives at it gradually, after years of practice, disciplining the mind that delights in distraction, learning how to focus all attention on a single thing. To focus completely on a single thing means to be able to let go of everything else. So, once you can do that, you can rid yourself from all undesired cognitive contents and enjoy a pure unmediated experience of reality. Now, if the Gamma wave frequency goes up as more of the brain is connected through gap junctions, it seems that advanced practitioners are simply able to network more of their brains, having trained to concentrate their minds. The benefits of meditation do not all wear off, advanced practitioners have a higher baseline gamma synchrony, suggesting a higher general awareness, concentration and consciousness. Other research has shown that meditation also thickens grey matter in parts of the cortex where it normally gets thinner with age.
Breakthrough study on EEG of meditation, Stuart Hameroff MD, Director, Center for Consciousness Studies, U. of Arizona-Tucson
