1. University of Wisconsin – Madison University of Wisconsin – Madison Engineering Projects In Community Service BIOFEEDBACK / STRESS MANAGEMENT May 9, 2001 Professor John Webster, Advisor Department of Biomedical Engineering Dr. Dan Muller, Client Department of Medicine and Med Micro/Immunology

2. Group Members Electrodes: Ben Birkenstock Ji Choe Elizabeth Nee Christy Palmer Feedback: Chris Koenigs Amy Li Electronics: Steve Almasi Jacob Feala William Lau Sarah Michaels

3. Problem Statement To design and build a portable, inexpensive electroencephalogram (EEG) device that would enable users to monitor brain states during meditation.

4. Meditation Self-induced calming of mind and body Self-induced calming of mind and body Linked to health benefits Linked to health benefits  ADD  Blood pressure  Creativity

5. Electroencephalogram (EEG) Electrodes attached to scalp Action potentials of cells amplified and averaged Oscilloscope provides visual representation of brain wave signals

6. Brain Wave States Beta: waking activity (above 13 Hz) Alpha: relaxed, eyes closed (8-13 Hz) Theta: drowsy, dreamlike (4-7 Hz) Delta: deep sleep (below 4 Hz) Meditation can alter brain waves over time

7. Subgroups Electrodes Electrodes Determine number, type, placement and attachment of electrodes Electronics Electronics Design and build circuitry Feedback Feedback Determine system of feedback to user

8. Basic Design Concept

9. Electrodes Elizabeth Nee

10. Electrode Selection Style Style  Reusable  Disposable  Dry/active Type of electrolyte  Gel  Paste  Saline  Hydrogel

11. Electrode Placement theta—central alpha—occipital

12. Current Design Pros Pros  Inconspicuous  Not distracting to user  Adjustable  Easy to place properly Cons  Possible noise  Problems achieving good contact through long hair side view rear view

13. Accomplishments This Semester Research Research  Full EEG electrode set-up not necessary  Placement of electrodes confirmed Existing products Existing products  Ordered FlexTrodes system  Investigated HydroDot electrodes Tested device Tested device

14. Electronics Steve Almasi

15. General Specifications Portable Portable  Small  Lightweight  Battery powered Inexpensive Inexpensive  Most existing products > $700 Measure strength of alpha ( a ) and theta ( J ) Measure strength of alpha ( a ) and theta ( J ) Provide feedback Provide feedback  Dominant state  Strength of dominant state

16. Signal Flow Diagram electrodesamplifier  filter (4-8 Hz) rectifier + averager audio output  filter (8-13 Hz) rectifier + averager voltage- controlled oscillator [from Gevins, 1994].

17. Signal Processing t v(t) original signalfiltered signalrectified signalaveraged signal [from Gevins, 1994].

18. Amplifier Specifications High input impedance High input impedance High noise rejection High noise rejection Amplify 10-100  V input signal Amplify 10-100  V input signal Minimal power consumption Minimal power consumption Low cost Low cost

19. Amplifier Design

20. Test Results Gain of approximately 19,000 at 10 Hz Gain of approximately 19,000 at 10 Hz High common mode rejection ratio High common mode rejection ratio Attenuated DC offset Attenuated DC offset

21. Filter Specifications Distinguish alpha, theta bands Distinguish alpha, theta bands Low complexity Low complexity Minimal power consumption Minimal power consumption Low cost Low cost

22. Alpha Circuit

23. Theta Circuit

24. Test Results

25. Feedback Amy Li

26. Specifications Make meditation more fulfilling Make meditation more fulfilling Pleasant, easy to understand feedback Pleasant, easy to understand feedback Low cost Low cost Technically feasible Technically feasible

27. Feedback Essential Points Starts with high pitched tone Starts with high pitched tone User chooses to train for alpha or theta state User chooses to train for alpha or theta state Pitch varies in proportion to strength of desired state Pitch varies in proportion to strength of desired state

28. Feedback Strategy High pitch High Volume Lower pitch Lower Volume * * *Attained Ideal Deep Meditative State* Silence Pitch and volume increases again If meditative state is lost Target 1. 2. 3. 4. 5.

29. Feedback Circuit - Summing Amplifier

30. Feedback Circuit - Variable Gain Amplifier

31. Research Results Best performed with eyes closed Best performed with eyes closed Auditory signals most effective Auditory signals most effective  Volume change difficult to detect  Pitch change easy to detect Vibrations, thermal signals, artificial tones less effective Vibrations, thermal signals, artificial tones less effective

32. Changing Tone Pros Pros  Technically simple  Less distracting than music  Easy to detect pitch change Cons  “tone deafness”  Intrusive sound

33. Questions?