Brain waves during meditation

During meditation there is a modest increase in slow alpha or theta wave EEG activity.

Chang and Lo found different results, explicable perhaps by the fact they show no sign of even having tested for gamma.First they classify five patterns in meditation based on the normal four frequency ranges (delta < 4 Hz, theta 4 to <8 Hz, alpha 8 to 13 Hz, and beta >13 Hz). The five patterns they found were:

1) delta

2) delta + theta

3) theta + slow alpha

4) high-amplitude alpha

5) amplitude suppressed ("silent and almost flat")

They found pattern No. 5 unique and characterized by:

1) extremely low power (significant suppression of EEG amplitude)

2) corresponding temporal patterns with no particular EEG rhythm

3) no dominating peak in the spectral distribution

They had collected EEG patterns from more than 50 meditators over the prior five years. Five meditation EEG scenarios are then described. They further state that most meditation is dominated by alpha waves. They found delta and theta waves occurred occasionally, sometimes while people fell asleep and sometimes not. In particular they found the amplitude suppressed pattern correlated with "the feeling of blessings."

O Nuallain,Sean (2009)  in Cognitive Sciences 4(2), is the first to interrelate the work on synchronized gamma in consciousness with the well-attested work on gamma in meditation in an experimental context. It adduces experimental and simulated data to show that what both have in common is the ability to put the brain into a state in which it is maximally sensitive and consumes power at a lower (or even zero) rate, briefly. It is argued that this may correspond to a “selfless” state and the more typical non-zero state, in which gamma is not so prominent, corresponds to a state of empirical self. Thus, the “zero power” in the title refers not only to the power spectrum of the brain as measured by the Hilbert transform, but also to a psychological state of personal renunciation.