Transcript Meditation
EEG Biofeedback Device Client: Dr. Daniel Muller Advisor: John Webster Ashley Anderson, Michelle Lorenz, Shikha, Ryan Thome, Chris Wegener University of Wisconsin - Madison Biomedical Engineering Design Courses INTELLECTUAL PROPERTY STATEMENT All information provided by individuals or Design Project Groups during this or subsequent presentations is the property of the University and of the researchers presenting this information. In addition, any information provided herein may include results sponsored by and provided to a member company of the Biomedical Engineering Student Design Consortium (SDC). The above information may include intellectual property rights belonging to the University to which the SDC may have license rights. Anyone to whom this information is disclosed: 1) Agrees to use this information solely for purposes related to this review; 2) Agrees not to use this information for any other purpose unless given written approval in advance by the Project Group, the Client / SDC, and the Advisor. 3) Agrees to keep this information in confidence until the University and the relevant parties listed in Part (2) above have evaluated and secured any applicable intellectual property rights in this information. 4) Continued attendance at this presentation constitutes compliance with this agreement. 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 http://openeeg.sourceforge.net/buildeeg/images • headband • sponge ear plugs Disadvantages: • elastic • heat shrink tubing • shielded audio cable • 5 pin DIN plug + socket - Setup is rather bulky • male plastic coax plug • table salt Total cost ≈ 50 dollars (electrolytic solution) - Electrolyte solution is salt water, leaving evaporation as a major issue 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. http://uazu.net/eeg/ae.html Pin Electrodes Continued 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. 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. Figure 1 Figure 2 Attached to color-coded shielded lead wires. Cost: $85-90 (for Set of 6) References: Text: http://openeeg.sourceforge.net/doc/hw/electrodes/ http://www.grass-telefactor.com/products/electrodes/electprecintro.html Figure 1: http://www.nihonkohden.com/products/supplies/eeg-electrodes.html Figure 2 and 3: http://www.electrodestore.com/EEG/EEG.lasso?ran=355D2CB5&S=10&T=37 Figure 3 Plate/Disc Electrodes Continued 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 Reference: Figure 1: http://www.adinstruments.com/products/product.php?id=MLAWBT9 Figure 2: http://openeeg.sourceforge.net/doc/hw/electrodes/ Figure 1 Figure 2 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 50μV P-P 4 – 15Hz Frequency Bandwidth Comparison of electrode designs Scale from 1 (lowest) to 10 (highest) Ease of manufacture Comfort Preparation simplicity Cost Aesthetics Durability (reusability) Overall Coaxial cable headband 8 6 8 9 7 8 7.6 Pin electrodes 2 4 10 4 7 10 6.2 Plate electrodes 10 4 2 1 3 6 4.3 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. Future Work • • • • Decide on digital or analog signal processing Choose feedback mechanism Test electrode signal quality Build amplifier prototype Questions?