I rarely, if ever, do any EEG biofeedback any more, but I wanted to take a look at my frontal EEG (F3 & F4) and see what was up. I had a 5 minute F3-F4 baseline from back in 2007 and decided to do a new 5 minute baseline and compare them. Around 2009, almost 3 years ago, I began meditating daily, about an hour a day, amassing easily over 1000 hours of good practice. During this time I attained stream-entry and vipassana-style access (but by no means mastery) to 8 jhanas. For the current data, I was lightly in 4th jhana, I can't seem to help it.
For the graphs, blue is old (2007), red is recent (2012).
On the left (F3) the changes were increased activation (expected increase in amplitudes, particularly of high frequencies). Alpha amplitude remained unchanged, while the amplitude of many other frequencies nearly doubled, a highly significant change. The old 2007 data has an interesting spike around 39 hz that might simply be artifact. The 2012 data shows an interesting low frequency bump in the delta range as well.
this research. I'd like to hear from a practitioner or something, but my guess would be that my original coherence levels might have been a little high. Looking around at some papers, that would seem to be the case, particularly as I used to have some problems with depression. I notice that the alpha and gamma coherence seems to have changed the least, while slow wave coherence is dramatically different, decreasing by 75%.