Fig. 1: Portable meditation biofeedback device in use: (1.a) Headband, including amplification component and detachable Ag/AgCl electrodes. (1.b) Bioamplifier and biofeedback circuitry enclosure.Fig. 2: Final Device Assembly: (2.a) Headband with all direct acquisition components connected. (2.b) Clip-on reference electrode included for DRL implementation. (2.c) Active electrode component. (2.d) Bioamplifier and biofeedback casing.Fig. 3 (3.a) Foam pad for user comfort with embedded, detachable electrode. (3.b) Active electrode component connected to Ag/AgCl electrode through a small slit in the headband.Fig. 4: Bioamplifier casing including (4.a) belt clip (4.b) temporary external 9 V battery connections, (4.c) bioamplifier circuitry and (4.d) 6 pin I/O connector.

Final DesignThe layout of our final design encompasses three distinct components – the active electrodes, the bioamplifier, and the headband.

Active Electrode Fabrication and Placement

Bioamplifier

Problem StatementTo design and build an inexpensive, portable electroencephalogram (EEG) that teaches meditation practitioners how to achieve optimal meditation by indicating the presence of EEG alpha and theta waves via auditory feedback. This shall be achieved through a relatively inexpensive, minimally distracting, and potentially portable device intended for commercial availability.

HeadbandThe final assembly is designed for easy setup and maintenance, comfort, and a simplistic appearance. The biofeedback headphones and a large cable exit the electromagnetic field (EMF) shielded bioamplifier, which clips to the users waist. The cable carries all power sources to the headband and all signals back to the bioamplifier. Each wire is a twisted, shielded wire to attenuate EMF interference.

The large cable supplies each active component, which is fastened to the outer surface of the headband, with power inputs. From the active components, wires move to the electrodes at the headband’s inner surface. The electrode disks detach from the female connector for quick and easy cleaning. Button snaps secure the electrodes near foam disks, which line the inner surface of the headband.

The smooth-surfaced, Velcro-fastened headband ensures enough pressure to maintain electrode-scalp contact without sacrificing user comfort. The back of each electrode is met with a needle sized hole in the headband; this allows the user to apply electrolyte gel into the disks with a syringe after the headband is attached.

AbstractThe physiological effects of meditation have been an active area of research in recent decades and are widely accepted to be highly beneficial for stress reduction and overall well-being [3,5,6]. As a result, many physicians have become increasingly intrigued by meditation’s clinical potential; developing a device to enhance one’s ability to reach a meditative state through biofeedback could prove to be a clinically significant tool. A compact, affordable device was designed and fabricated to acquire clean, human electroencephalogram (EEG) signals and provide auditory feedback upon detection of alpha and theta waves. These rhythms are believed to be strongly linked to the “bliss” state of meditation [1,2]. Computer simulations have verified the theoretical functionality of the device. Human testing will be conducted to determine its true effectiveness.

Background

the mass action potential activity of the neurons in the brain. This can give the clinician a means to quantitatively analyze brain activity.

Most of the time, brain waves are seemingly random and no general pattern is observed. However, during specific behaviors, a distinct pattern can be seen. Brain waves are characterized into one of four groups - alpha, beta, theta, and delta.

Meditation is generally associated with the presence of alpha (8-13 Hz) and theta (4-7 Hz) EEG activity [1,2]. Meditation has been shown to have many beneficial physiological effects, including decreased stress, blood pressure, and anxiety [3,5,6].

Future WorkMultiple potentiometers were included in the initial prototype to allow for variable gain at each of the amplifier components. This will allow us to determine the optimal gain values at each stage, leaving us with the option of either increasing, decreasing, or removing the gain of the active electrodes. Preliminary testing will focus primarily on finalizing all resistor values and evaluating the merit of the driven right leg reference and active electrode designs for subsequent prototype generations. In addition, we will assess current draw, average battery life, and noise influence on the device. Following the debugging phase of preliminary testing, we will advance to human subject testing on sleep lab patients and students with advanced meditation abilities.

In parallel with device testing, we will modify multiple facets of the design. We will modify the circuit to function with a single 9 volt battery; this will permit us to reduce size and weight of the bioamplifier. We will also pursue commercialization and development of a marketing model for this product. To increase marketability, we will improve final assembly ergonomics and aesthetics; most importantly we will focus on the headband and electrode attachment including but not limited to: adjustable electrode location, headband fastening mechanism, and headband material.

• Filters (Gain = 10)-Alpha (8.5 – 15Hz)-Theta (0.5 – 7.5Hz)

• Additional Gain (20-1000)• Isolation

-Decouple output from input

• Rectifier and Averager-Generate DC voltage

• Variable Frequency circuit-V/F converter-Constant Amplitude-Changing frequency with changing brainwaves

• Variable Amplitude circuit-555 timer-Constant frequency-Changing amplitude with changing brainwaves.

• Headphones

EEG Biofeedback SystemAndrew Eley, Joseph Hippensteel, Prakash Rao, & Cullen RotroffDepartment of Biomedical Engineering, University of Wisconsin

Client: Daniel Muller, M.D., Ph.D, Dept. of Medicine - Rheumatology Advisor: Willis Tompkins, Ph.D, Dept. of Biomedical Engineering

Cost Analysis

Single prototype production costs Production costs for 10,000 units $73.80 per unit $42.70 per unit

Electroencephalography is used by clinicians to measure the electrical activity of the brain. This is done by placing electrodes on the scalp, specifically the cerebral cortex, and measuring the resulting voltages. The voltages are caused by

Works Cited[1] L. I. Aftanas and S.A. Golocheikine, “Human anterior and frontal midline theta and lower alpha

reflect emotionally positive state and internalized attention: high-resolution EEG investigation of meditation,” Neuroscience Letters, 310, pp. 57-60, 2001.

[2] J. P. Banquet, "Spectral analysis of the EEG in meditation," Electroencephalogr. Clin. Neurophysiol., vol. 35, pp. 143-151, Aug. 1973.

[3] M. M. Delmonte, "Electrocortical activity and related phenomena associated with meditation practice: a literature review," Int. J. Neurosci., vol. 24, pp. 217-231, Nov. 1984.

[4] E. Felton, Personal Correspondence. October 19. 2006. [5] R. Jevning, R. K. Wallace and M. Beidebach, "The physiology of meditation: a review. A wakeful

hypometabolic integrated response," Neurosci. Biobehav. Rev., vol. 16, pp. 415-424, Fall. 1992. [6] J. Kabat-Zinn, A.O. Massion, J. Kristelle, L.G. Peterson, K.E. Fletcher, L. Pbert, W.R.

Lenderking, and S.F. Santorelli, “Effectiveness of a meditation-based stress reduction program in the treatment of anxiety disorders,” Am J Psychiatry, 149, pp. 936-943, 1992.

One of the primary novelties of the current design when compared to previous proposals is the use of an active electrode component (Fig. 2) to increase signal quality. Noise, excluding motion and electromyogram artifact, is proportionally reduced as a result of amplification implemented near the signal source.

Silver, silver-chloride (Ag/AgCl) electrodes (Fig. 3a) were chosen based upon correspondence with a graduate student actively using EEG technology in her research [4]. Three electrodes are included in the design; two for neural activity recording and one that is clipped onto the user’s ear as a reference (Fig. 2b). A driven-right leg (DRL) circuit is used to interface the reference electrode with the remainder of the amplifiercircuit. This scheme is believed to have sufficient resolution to acquire alpha and theta waves from the human cortex. Optimal electrode placement was determined following a literature search, revealing that alpha and theta activity are prominent in the frontal and occipital lobes during meditation [1,2].

The active components are connected to the two acquisition electrodes and consist of a simple micro-power operational amplifier (op-amp) circuit. The final op-amp circuit was printed on a custom printed circuit board (PCB) and requires 2 micro-resistors.

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