Aug 142015
 

One of the oldest and most studied phenomena of EEG research has been the study of alpha rhythms. These oscillations, at a frequency of around 10Hz occur reliably in awake healthy individuals in a relaxed state with their eyes closed.  The beginning instructions for zazen meditation are to sit quietly, in an alert but relaxed state, to count one’s breaths while keeping the eyes open.

The first experiment I wanted to try was to do this simple exercise of counting the breath and compare the conditions of eyes closed with eyes open. In both cases, I tried to avoid moving my eyes but instead keep them directed at a point on the floor a few feet in front of me. I set a timer on my smartphone that gave me soft spoken word “Now” every 7 minutes. Sessions last 21 minutes each and included alternating segments of eyes open and eyes closed, sometimes starting with open, other times starting with closed. I tried to keep everything else the same during the recordings, which included four segments of eyes closed and four segments of eyes open.

The radar charts below show median values averaged over the four session segments.

Eyes closed

Counting breaths with eyes closed (relative band power averaged over four recordings)

Eyes open

Counting breaths with eyes open (relative band power averaged over four recordings)

While alpha rhythm was stronger overall with eyes closed, the higher frequency bands beta and gamma were more prominent with eyes open, especially in the left frontal region. This confirmed that yes, indeed, from my brain, different EEG patterns result from different body conditions.

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