These data came from a 20-minute session with four 5-minute segments: drinking tea, counting my breath, thinking of tools and following my breath. During the first segment, I sat quietly and let my mind wander. Periodically, I reached for my teacup periodically and took a a sip. In the latter three segments, I continued sitting in zazen posture with open eyes gazing at a fixed point on the floor.
During the first segment, drinking tea, the low frequency delta component was relatively strong. The question arises as to whether low frequency delta oscillations correspond to mind wandering (or only tea drinking!).
Delta component has decreased while alpha component has increased. There is some increase in the beta and gamma bands as well.
Beta and gamma power is definitely stronger during this segment and delta is less.
Higher frequency bands (beta and gamma) are reduced and alpha has increased a bit.
These results, taken from four successive 5-minute segments during a single round of sitting are consistent with the results from a previous post, which were taken from the initial three minutes of three separate rounds. In both cases, alpha predominates for counting or following the breath while beta and gamma are stronger during reading or thinking of things.