EEG Biofeedback Team: Cullen Rotroff, Andrew Eley, Prakash Rao, Joseph Hippensteel BME 400 October 27th, 2006

Client: Dan Mueller, Ph. D Client: Dan Mueller, Ph.D. Medicine (Rheumatology) Institute on aging, Mind-body Center Advisor: Professor Willis Tompkins, Ph.D. Dept. of Biomedical Engineering University of Wisconsin

Overview Problem Statement Background Design Constraints Proposed Designs Future Work Questions

Problem Statement To Design and build an inexpensive, portable electroencephalogram (EEG - brain wave monitor) that teaches meditation practitioners to achieve optimal meditation by indicating the presence of EEG alpha and theta waves. This shall be achieved through a relatively inexpensive, minimally distracting, and potentially portable device intended for commercial use.

What is Meditation In pop culture/alternative medicine, meditation is a technique for achieving “inner peace”. Allows access to a naturally-occurring rest state. Different from sleep, in that rest via mediation is much deeper and happens more quickly.

Benefits of Meditation Spiritual Enrichment Facilitates Creative Awareness Psychological Benefits Increased Patience Heightened Sensation Reduced Stress (Kabat et al. 2001) Improved Stress Recovery Increased Response Time Decreases Recovery Time from Illness

Physiological Response to Meditation Decreased metabolic rate Decrease oxygen consumption (up to 20% below normal level) Lowered heart rate 2 less breaths per minute on average Decreased levels of lactate (linked to anxiety symptoms), cortisol, and epinephrine Raise skin resistance Increased blood flow Presence of Alpha (8-13 Hz) and Theta waves (4-7 Hz).

Brain Wave Frequencies Brain-Wave Frequency State of Consciousness Brain Wave Sample BETA: above 13 Hz Fully-Awake, Alert, Excitement, Tension ALPHA: 8 to 13 Hz Deeply-Relaxed, Passive-Awareness, Composed THETA: 4 to 7 Hz Drowsiness, Unconscious, Deep-Tranquility. Optimal Meditative State DELTA: Below 4 Hz Sleep, Unaware, Deep-Unconsciousness

Product Requirements Small in size, simple in design (like an iPod) Portable Low cost (~ $100 - $200) Provide auditory feedback that won’t disrupt meditative state Long-term: Marketable

Competition Computer automated EEG biofeedback Expensive (range from $1,200 - $6,000+) Non-portable systems Superfluous detection abilities GSR (Galvanic Skin Response) biofeedback Conductivity of skin to indicates stress level Prices average ~$100.00 Less reliable than EEG biofeedback http://www.sciencekit.com/category.asp_Q_c_E_737808

Competition AUTOGENIC AT62 PORTABLE EEG Alpha and theta filter Dual audio feedback modes Signal proportional Pitch change On/off threshold verification Visual ‘Lightbar’ display varies with brainwave state Real Time EEG display $1,550.00

Project Flowchart { Primary Focus { Future Work

Electrode Design Passive Electrodes Traditional EEG electrodes Ag/AgCl Standard Also available: Tin, Silver, Gold No amplification Requires low impedance skin contact (Electrolyte gel) Easy to clean Price: ~$6 per unit (http://www.rochestermed.com/Electrodes.htm) http://bhgcoleman1.trustpass.alibab a.com/product/10948731/Gold_EEG _Large_Electrode_Cup.html

Electrode Design Active Electrodes Use Ag/AgCl substrate First stage amplification moved to electrode site Tolerates higher impedances if desired Shortens skin preparation time Lessens potential for electric shock Improves signal clarity Diminishes 60 Hz noise Reduces problems with capacitive coupling Very expensive commercially (cost up to $395 per electrode) http://electrodesales.stores.yahoo.net/tsd150a.html

Electrode Comparison Weight Active (Fabricated) Active (Purchased) Passive Cost 5 4 1 Production 3 Power Consumption 2 Safety Noise Reduction Maintenance Total 95 80 74 75

voltage-controlled oscillator Circuit Flow Diagram q filter (4-8 Hz) rectifier+ averager voltage-controlled oscillator audio output Amplifier/DRL a filter (8-13 Hz) rectifier+ averager Electrodes/amplify

Bio-Amplifier Raw signal is noisy and on the order of microvolts Need great amplification and fine-tuned filtration Typical specifications for EEG Amplifiers: Gain: 4-5 dB 2nd order BP filter

Bio-Amplifier Amplification Instrumentation Amplifier High input impedance High CMRR* Gain: ~25 Driven Right-Leg Used as “reference point” Lowers common-mode voltage

Bio-Amplifier Filtering Theta LP – fc = 8 Hz Alpha BP – BW = 9.7-12Hz Gain ~ 4500 for both channels, 5th order

Filter Frequency Response

Bio-Feedback Signal Conditioning Rectify signal Average signal Voltage Controlled Oscillator (VCO) Translate voltage to audible frequency

Future Work Validate bio-amplifier design P-Spice Simulation Bread-board prototype Fabricate final bio-amplifier Complete active electrodes Finalize Bio-feedback design Integrate all components Clinical testing with subjects

Questions?

References Aftanas LI and Golocheikine SA. “Human anterior and frontal midline theta and lower alpha reflect emotionally positive state and internalized attention: high-resolution EEG investigation of meditation.” Neuroscience Letters 2001; 310. 57-60. Kabat-Zinn J, Massion AO, Kristelle J, Peterson LG, Fletcher KE, Pbert L, Lenderking WR, Santorelli SF. “Effectiveness of a meditation-based stress reduction program in the treatment of anxiety disorders.” Am J Psychiatry 1992; 149. 936-943.

Electrode Placement Primary activation during meditation Fp1/Fp2 F3/Fz/F4 O1/O2 (Aftanas and Golocheikine 2001)