1. Professor John Webster, Advisor
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: Electronics: Feedback: 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
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
Determine number, type, placement and attachment of electrodes
Electronics
Design and build circuitry
Feedback
Determine system of feedback to user

8. Basic Design Concept

9. Electrodes
Elizabeth Nee

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

11. Electrode Placement
theta—central
alpha—occipital

12. Current Design Pros Cons Inconspicuous Possible noise
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
Full EEG electrode set-up not necessary
Placement of electrodes confirmed
Existing products
Ordered FlexTrodes system
Investigated HydroDot electrodes
Tested device

14. Electronics
Steve Almasi

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

16. voltage-controlled oscillator
Signal Flow Diagram
q filter
(4-8 Hz)
rectifier+ averager
voltage-controlled oscillator
audio output
electrodes
amplifier
a filter
(8-13 Hz)
rectifier+ averager
[from Gevins, 1994].

17. Signal Processing original signal filtered signal rectified signal
v(t)
original signal
filtered signal
rectified signal
averaged signal
[from Gevins, 1994]. t

18. Amplifier Specifications
High input impedance
High noise rejection
Amplify mV input signal
Minimal power consumption
Low cost

19. Amplifier Design

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

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

22. Alpha Circuit

23. Theta Circuit

24. Test Results

25. Feedback
Amy Li

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

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

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

29. Feedback Circuit - Summing Amplifier

30. Feedback Circuit - Variable Gain Amplifier

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

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

33. Questions?