The previous study which used average mean band power over meditation intervals of 10-15 minutes did not reveal a strong correlation with meditation experience. However, a recording made on the 3rd day of a 7-day sesshin showed a linear increase in beta and gamma power over a single round of meditation. Should we be looking not at the average over a whole period, but rather focus on a “best” interval near the end of the period?
What would happen if we selected a 2-minute interval near the end of the period and used the mean absolute power for that short interval as a measure of the meditation?
To find out, I reexamined the EEG recordings for each of the thirty subjects in the sample, selecting a “best” 2-minute interval near the end of the meditation. Results for beta power at the front sensors are shown below:
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Results for alpha power at the back sensors gives us the following:
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It looks as if our analysis using “best 2-minute” intervals doesn’t provide any more suggestion of a correlation between band power and hours of meditation as the previous analysis using the whole interval of meditation.
Further investigation was in order. Instead of using the mean absolute power over selected intervals, I chose to examine peaks in the Power Spectral Density graphs as another avenue of research.