EEG Biofeedback Device Ashley Anderson, Michelle Lorenz, Shikha, Ryan Thome, Chris Wegener Client: Dr. Daniel MullerAdvisor: John Webster

Problem Statement Design and build an inexpensive, portable electroencephalogram (EEG) that teaches meditation practitioners to achieve optimal meditation by the presence of EEG alpha and theta waves.

Meditation Proven form of alternative medicine Epilepsy Addiction AD/HD Mood Disorders Learned ability Allows self-detachment and relaxation

Electroencephalograph Measure surface voltage on the scalp Brain activity type inferred by frequency Target frequencies: Alpha (Relaxed) 8-15Hz Theta (Meditative) 4-7Hz

Design Constrains Handheld/Portable Inexpensive (<$100) Easy to use Must provide interpretable feedback Unintrusive Comfortable

Coaxial cable headband design overview + components Advantages: - Utilizes economical and user friendly materials (no lengthy preparation necessary) - Electrode arrangement desirable (frontal placement successful in previous groups) parts list headband elastic shielded audio cable male plastic coax plug Disadvantages: - Setup is rather bulky - Electrolyte solution is salt water, leaving evaporation as a major issue sponge ear plugs heat shrink tubing 5 pin DIN plug + socket table salt (electrolytic solution) Total cost ≈ 50 dollars

Coaxial cable headband design additions/improvements - Wedges as a component of the headband (either included in the band or added by us) to part the hair for better scalp contact or manufacture of individual electrodes utilizing concept of a simple hair clip/comb to move hair away from scalp - Electrolyte medium: current proposed mixture is messy, goal is a non-irritating solution or gel that reduces oil on scalp and maximizes conductivity

Pin Electrodes An array of metal conducting pins are fixed to an electrode base board. Between 16 and 32 holes are drilled in the base board and the pins are soldered in place from the back. Two separate electrodes are attached to a headband and held firmly against the scalp.

Pin Electrodes Advantages Does not require abrasive skin cleaning or messy conducting gels Pins are able to burrow through the hair and make direct contact with the scalp Electrodes are reusable Disadvantages Lack of conducting gel may result in poor signal quality Lack of adhesive leaves the electrode prone to sliding along the scalp, causing signal interference. Continued

Plate/Disc Electrodes Features:  Most commonly used electrode today in EEG biofeedback devices.  The disc electrodes consists of a flat disc generally of diameter 6mm – 10mm.  EEG disc electrodes feature a hole in the top for electrolyte injection.  Attached to color-coded shielded lead wires.  Cost: $85-90 (for Set of 6) References: Text: Figure 1: Figure 2 and 3: Figure 1 Figure 2 Figure 3

Plate/Disc Electrodes ADVANTAGES: Easy to make (just buy them!) Passive Electrodes Pleasing Aesthetics DISADVANTAGES: Bad conductivity and signal Difficult to use/meditate Dependence on gel Expensive: Extra cost of gel Difficult to clean Figure 1 Figure 2 Reference: Figure 1: Figure 2: Continued

Amplifier Constraints Low cost Clear, accurate signal Portable Battery powered Minimal size and weight Safe to use

Amplifier Design High input impedance Common Instrumentation Amplifier Design High CMRR, amplify 50 μ V P-P 4 – 15Hz Frequency Bandwidth

Ease of manufacture Comfort Preparation simplicity CostAesthetics Durability (reusability) Overall Coaxial cable headband Pin electrodes Plate electrodes Comparison of electrode designs Coaxial cable and pin electrodes both reasonably match our project design goals, but further differentiation will depend upon signal strength and quality which we hope to learn from future experiments. Scale from 1 (lowest) to 10 (highest)

Future Work Decide on digital or analog signal processing Choose feedback mechanism Test electrode signal quality Build amplifier prototype

Questions?