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Biofeedback Experiments 1

July 21, 2007


I sporadically practice meditation. As soon as I started, I was curious about what is going on with the brain and body during meditation. The biofeedback game, The Journey To Wild Divine,  uses a simple USB 3-finger sensor called the LightStone that measures heart rate and skin conductance give a simple answer to that question. These are two readily measurable quantities with patterns people associate with meditation practice.

Here is a nice description of The Journey To Wild Divine, reviewed for the Mac.

I tried out a friend’s copy late one Friday night and was out getting my own within a few weeks.  After a few sessions, I completed the game and came back to practice some of the exercises with the data recording feature turned on ($).

The JWD game exports the instantaneous heart rate (IHR), the (calculated) heart rate variation (HRV) and skin conductance level (SCL).  There are some open source programs for acquiring and analyzing the LightStone data. I just dumped the data into Mathematica via a Python import script.

The game presents visual “puzzles” (e.g. stack levitating rocks, unlock doors, etc.) one “solves” by controlling the readings on the LightStone.  Some require becoming more energetic (agitated?), and many require great relaxation and steady attention. Below are the recordings from (what I found) a challenging exercise in the game.  It took maybe 10 or more minutes.  It is hard to keep track of time when you are solving the puzzles, and I didn’t time myself.  (I haven’t taken the effort to figure out the time scale on the exported data yet.)

 SCl Plot

The most dramatic (graphically) change over the exercise was the decrease in SCL.  At the beginning of the exercise, SCL is relatively high and unsteady.  It decreased steadily with small sharp jumps upward until the puzzle was solved. (The change in pattern of all three quantities is visible when the puzzle was solved a little before the end of the recording.)


HRV Plot



The HRV scale is in arbitrary units (i.e., I don’t understand them yet).  There seems to be research and claims (and gadget-programs!) regarding the correlation between higher HRV and good health. Ah, causality.  Anyway, in order to solve the puzzle in JWD, it appears that I had to raise my time-averaged HRV. (I don’t know the actual formula.)

 IHR Plot

The last graph shows the IHR.  This one I think I understand.  JWD use a heart beat pattern recognition algorithm to detect the spike in every heart beat and use that to mark the time between individual beats. The IHR is proportional to1/(time between two adjacent peaks).

The IHR starts out erratic, but settles into a pattern that raises and falls in relation to my respiration (it seems).

This is fun. Measuring a couple of readily available metrics started me thinking about the possibilities or getting to key points in other systems simultaneously.  For example, it is easy to imagine that my endocrine system is involved, and so that metabolism is affected. And on and on…Our systems-level understanding of the body is very primitive, but the opportunities for deep understanding are starting to seem within reach.

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