Electroencephalogram Biofeedback

Jnane Abdelhamid

Mentor: Dr.Marom Bikson

Biomedical Engineering Department

The City College of New York

CUNY

I-Abstract

Meditation is a proven alternative medicine and is effective in combating diseases such as stress reduce, epilepsy, mood disorders, addictions. Meditation involves altering patients’ state of mind, so it can be quantified by brain waves. A common obstacle among people learning how to meditate is determining whether they have achieved the optimal brain states required for effective meditation. The purpose of this project is to provide brain activity feedback so meditation practitioners know when they have reached the correct meditative state. The ultimate goal is to design and build an inexpensive, portable electroencephalogram (EEG), which provides brain activity feedback for a user-friendly game to help users to learn how to meditate effectively. The EEG device was designed to detect the alpha and theta frequencies , which correspond to meditative state.

The design of this device will detect a person’s brain state by measuring brain waves with electrodes. Then, the brain waves would be selectively filtered and amplified eliminating any noise. Lastly, the brain wave would be turned into some sort of biofeedback signal, such as a light or a sound to notify the user what brain state they are in, alpha or theta, and how close to meditation they are. The final prototype of this device was fabricated and tested for alpha wave, which is the wave for meditative state. This design was achieved through the use of the following stage: signal acquisition phase using standard Ag-AgCl reusable solid gel electrodes, biomedical amplifiers using instrumentation amplifier, fifth order band pass filter, and finally feedback phase using d-flip-flopped for the light game. The signals were thoroughly tested by the national Instruments’ LabVIEW using NI-DAQ data acquisition board. The human test shows that our circuit works perfectly in detecting the theta wave (8Hz-14 Hz).

Finally, the EEG portable device was turned to a game. The alpha ROULETTE is a light (2.7 lb) portable game that detects alpha and theta wave signal to play roulette via the activation of light emission diode (LED) indicators. The LEDs randomly turn on and off as the user engages in activities that result in predominant alpha wave biopotential such as closing of eyes, concentration and/or relaxation. When the user stops concentrating or opens their eyes, only some lights will remain on. Before starting the game, players can predict and place bets on the final lit LED set up. This game is guaranteed to function under conditions that are specified in the manual.

Problem Statement

The final goal of this design project is to design and build an inexpensive, portable electroencephalogram EEG that teaches meditation practitioners to achieve optimal meditation by the presence theta waves and the following steps were followed:

1. Select electrode sites2. Select appropriate electrodes3. Designing a biomedical amplifiers using instrumentation amplifier4. Designing a high order band pass filter,5. Designing a feedback phase using light or sound.6. Turning the Biofeedback into an alpha roulette game, a suitable feedback stimuli

that would provide feedback that will positively reinforce meditative states.7. Integrate the system into a compatible prototype8. Assemble and evaluate the system

Introduction

A large number of physicians are recommending meditation, along with traditional medical treatments, in order to improve physical health and mental condition. Many studies have shown that meditation can be an effective treatment to reduce stress, anxiety, and mild hypertension. For instance, medication has proven to be effective treatment of attention Deficit Disorder, headaches, arthritis pain, psoriasis symptoms, insomnia and epileptic seizures. Meditation also has promising applications in relieving certain allergies and asthma. This is just an example of a few of the specific health benefits of meditation and more continue to be discovered every year.

Practitioners of meditation usually do not know whether they have successfully attained the brainwave states required for effective meditation. The two brainwave states of meditation are alpha and theta. The alpha state (8 to 13 Hz) often occurs when a subject is feeling drowsy or relaxed, and is best measured in the occipital lobe of the brain. The theta state (4 and 7 Hz) is characterized by a dreamlike awareness, and is linked with intense creativity.

Figure 1 : Brain Wave Frequencies

Meditation is a technique for achieving “inner peace”. It Allows access to a Meditation is a technique for achieving “inner peace”. It Allows access to a naturally-occurring rest state different from sleep, in that rest via mediation is much naturally-occurring rest state different from sleep, in that rest via mediation is much deeper and happens more quickly.deeper and happens more quickly. Meditation involves one altering their state of mind, so it can be quantized by brain waves. As seen in figure 1, the brain is in one of four states at any given time.

The aim of this project is toto Design and build an inexpensive portable electroencephalogram Design and build an inexpensive portable electroencephalogram (EEG - brain wave monitor) intended for commercial use. The device will teach meditation (EEG - brain wave monitor) intended for commercial use. The device will teach meditation practitioners to achieve optimal meditation by indicating the presence of EEG alpha and thetapractitioners to achieve optimal meditation by indicating the presence of EEG alpha and theta waves.waves. Current products on the market are very expensive and they offer more features than necessary

Prior Art and Competition

Computer automated EEG biofeedbackComputer automated EEG biofeedback

•Expensive (range from $1,200 - $6,000+) •Expensive (range from $1,200 - $6,000+) •Non-portable systems•Non-portable systems

GSR (Galvanic Skin Response) biofeedbackGSR (Galvanic Skin Response) biofeedback

•Conductivity of skin to indicates stress level•Conductivity of skin to indicates stress level•Prices average ~$100.00•Prices average ~$100.00•Less reliable than EEG biofeedback•Less reliable than EEG biofeedback

AUTOGENIC AT62 PORTABLE EEGAUTOGENIC AT62 PORTABLE EEG

• Alpha and theta filter• Alpha and theta filter• Dual audio feedback modes• Dual audio feedback modes• Signal proportional Pitch change• Signal proportional Pitch change• Visual ‘Lightbar’ display varies with brainwave state• Visual ‘Lightbar’ display varies with brainwave state• Price ~ $1,550.00• Price ~ $1,550.00

Figure 2: GSR Figure 3: Autogenic AT62

Circuit Design: The circuit design utilizes small voltage potentials from the electrodes on the cranial surface and filters out specific frequencies. A block diagram shows the different stages of the circuit (Figure 4).

Figure 4: Project flowchart depicting all stage of the device including preamplifier for small voltages (uV) from electrodes; Switch: Calibrator knob for voltage calibration; Dual flip flap for feedback of 64 binary.

Preliminary Amplification

Figure 5 and 6 show the schematic of two preamplifier that can be attached to the electrodes. This circuit both amplifies the signal (gain of 50,000) and cuts of high frequency. The circuit shown in figure 5 which the differential amplifier was used because has high Common-Mode-Rejection Ratio (CMRR).-Mode-Rejection Ratio (CMRR).

Figure 5: Differential Amplifier Figure 6: Instrumentation Amplifier

Circuit Schematic

Circuit Schematic

Figure 7: schematic of the device shown 3 electrodes for data acquisition; preamplifier, 5th order law pass filter, and 3 flip flapper for 65 binary output and switch.

Fabricated EEG device

Figure 8 : fabricated EEG device casing and layout

1. DEVICE COMPONENT

1.1 ON/OFF SWITCH & POWER INDICATOR: When the switch is turned on a red LED will indicate that the game is ready for use. To turn off the game or to reset, the user should press the switch again and the red LED will turn off. If the switch is turned on and LED does not turn on the batteries need to be replaced.1.2 BIOPOTENTIAL CALIBRATOR: Adjusts to your level of alpha wave biopotential. Must be calibrated for each new user immediately before playing the game.

1.3 LEAD ELECTRODES: Three color-coded ECG electrodes; red and white leads attach to the back of the head and the black lead attaches to the back of the ear as shown in QUICK START GUIDE. The electrodes are to be connected in these positions to ensure optimal transmission of signal.

1.4 ROULETTE LIGHTS: Five LEDs will light up and turn off in sequence. The objective of this game is to have the predicted LED lit when no longer engaged in alpha level such as when the user opens their eyes.

2. QUICK START GUIDE

2.1 Turn system on by pushing on the ON/OFF button once. Red LED should turn on to indicate that system is ready to use.

2.2 Plug in connectors of electrodes into the front panel of game

Figure 9: schematic of top panel of game Figure 10: front panel of game

2.3 Place electrodes in the positions illustrated in diagram below.

Figure 11: Electrode location in brain

2.4 Make sure that you have enough electro-conductive gel between the electrode and your scalp.

2.5 Predict and place bets. Close your eyes and relax, and you are ready to play the ALPHA ROULETTE. Turn switch off and back on to restart game.

3. DEVICE PERFORMANCE

3.1 INTRODUCTION: The ALPHA ROULETTE has gone through several tests for device performance under normal user activity. The protocols of these tests are laid out in this section of the DEVICE MANUAL.

3.2 SAFETY: This device does not require a wall power source in order to minimize possibilities of power hazards. The device uses only lead free components. The super conductive electrolyte gel is hypoallergenic and non-carcigenous. This game is not fit for children under five due to small components that pose a choking hazard.

3.3 SHAKE-TEST: The game was shifted from left to right with a three inch displacement for twenty cycles while user was playing the game without disruption. When the game underwent the same test in the vertical direction, it also withstood twenty cycles without disruption.

3.4 DROP-TEST: During device testing the ALPHA ROULETTE was dropped from the work table (about four feet from the ground). The device withstood the drop and

remained functioning afterwards. The drop test was repeated several times with the same results.

3.5 BATTERY LIFE: Panasonic 9V batteries have a continuous lifetime of 20 hours. However, our device has shown to drain the battery after about eight hours of continuous use. After the battery is drained, the ON LED turns off and the game is not operational until batteries are changed.

3.6 MOTION OF COMFORT: Since the electrodes are placed on the region where the occipital lobes are located and one behind the ear, there is a full range of motion for the user. Three test users were asked to move their heads up and down and in the radial direction. Afterwards the users were asked to stand up and sit down with the electrodes connected. All three user reported that they did didn’t experience any discomfort while performing this tasks and that the device performance was not disrupted. Even though the main objective of this game is to remain motionless in a calm and relaxed state, the game does not interfere with normal range of motion.

3.7 ANTI-TUG MECHANISM: All leads are not directly connected to the circuit. The electrodes have a female-male mechanism, which snaps on and off if tugged on. Consequently, any unsuspected tug will not result in the disturbance of the circuit. Moreover, the advantage of having removable leads is that the user can replace them if they are damaged.

3.8 HUMIDITY/TEMPERATURE CHANGE: Under the given circumstances, there was a limit to testing extreme conditions with regards to humidity and temperature change. The range of temperature of the provided facility and equipment only allowed for 20o

centigrade temperature variation. Under this variation there were no observed malfunctions of the game. The humidity was not tested due to lack of equipment. Whether the device is waterproof is not determined. However, certain precautions were taken to address these issues. First, there are no exposed wires. Second, the case is sealed air-tight. Finally, there is good insulation around the circuit for further protection.

3.9 ELECTRODE WEAR & TEAR: All electrode pads are disposable. The user can play the game for four hours. Furthermore, electrode wires could be replaced if malfunctioning. The effects of the electrodes on high perspiration have not been studied, although the manufacturer of the super conductive electrolyte gel contends that perspiration causes minimal effect.

3.10 USER FRIENDLY GAME: The entire OPERATIONAL MANUAL is only five steps. No complicated calibrations need to be done before starting the game. In fact, a first-time user just needs to be concerned with the proper placement of electrodes before starting the game. All game components are labeled clearly. The game component has a very simple objective and can be readily played by a person without any technical background.

3.11 FINAL RESULT OF PERFORMANCE: All of the tests that have been performed yielded to the result that the ALPHA ROULETTE is a robust and functional game.

Signal Processing Stage

The EEG signal that is transmitted from the lobe of the brain through the electrodes is on the order of 12 V. This signal is ultimately imported into the computer through a DAQ module. The main pathway for the signal is through a stage 5 th order law pass filter, FFT, statistical maximum value, and ultimately a threshold limit. The signal goes through these paths in parallel for each stage in the mediation and figure 12 shows three signals stage : impulse response, magnitude response and gain response. The magnitude response shows that frequency around 10 Hz which very good result of alpha wave.

Figure 12: shows impulse response, magnitude respond and phase response for band pass filter.

Figure 13: shows second trial of impulse response, magnitude respond and phase response for band pass filter

Figure 14: shows third trial of impulse response, magnitude respond and phase response for band pass filter

Conclusion

For all configurations a good EEG the device detected signal as shows in the graphs above generated by LabView. The prototype has been determined to be a working solution to the design problem and mostly satisfies the Product Design Specifications. Further research and development must be applied to obtain a reliable electrode system that is operable by a novice practitioner and outputs a cleaner EEG signal. Most likely this will require superior electrodes with a glue system.

References

1-Brain Waves & Soundhttp://www.educationalcoach.co.uk/brainwave.htm

2-Allen, Colin. “The Benefits of Meditation”http://www.psychologytoday.com

3-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.

4-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 Psychiatry 1992; 149. 936-943.Appendix:

Using a Multiple-Feedback Active Bandpass Filter

Alpha Filter (8 – 13 Hz desired)We want a Q of 3, a fc of 10 Hz using C = 0.1 F.Note: fc is 13 Hz to offset amplifier gain increase as frequency falls

Gain = Av = = 1

R1 = = = 477.46 k

R2 = = =28.086 k

R3 = = = 954.93 k