What can Electrophysiology tell us about 'meditation'

Jean-Philipe Lachaux

Basically, I wish to emphasize the fact that electrophysiology has told us
very little about the effect of meditation on the brain, especially
compared to what it will tell us in the years to come. EEG/MEG studies have
mainly focused on the spectral changes induced by meditation : augmentation
of power in certain frequency ranges, such as alpha, and diminution in
others. But without a proper understanding of the functional role of those
rythms, it is hard to really infer what those changes mean precisely,
beyond rough switches between major brain states. I will argue that the
brain rythms have in fact very precise and specific cognitive correlates,
when they are studied with a precise spatial resolution : an increase of
EEG activity in the gamma range (>40 Hz) in the visual cortex doesn't have
the same meaning as a similar increase in the motor cortex, or the
prefrontal cortex; and the same for the other frequency ranges. When brain
oscillations are analyzed at the level of functionally homogenous neural
populations, they are found to correlate with quite subtle aspects of
cognition, such as short attentional blinks, the emergence of quick
thoughts (the little voice in the head talking), rapid aspects of executive
control. It is at this level, that the effects of meditation should be
studied, optimally.