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

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

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

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

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

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

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

Basic Design Concept

Electrodes Elizabeth Nee

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

Electrode Placement theta—central alpha—occipital

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

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

Electronics Steve Almasi

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

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].

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

Amplifier Specifications High input impedance High noise rejection Amplify 10-100 mV input signal Minimal power consumption Low cost

Amplifier Design

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

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

Alpha Circuit

Theta Circuit

Test Results

Feedback Amy Li

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

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

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.

Feedback Circuit - Summing Amplifier

Feedback Circuit - Variable Gain Amplifier

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

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

Questions?