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.

1
EEG Biofeedback System Andrew Eley, Joseph
Hippensteel, Prakash Rao, Cullen
Rotroff Department 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

• Final Design
• The layout of our final design encompasses three
  distinct components the active electrodes, the
  bioamplifier, and the headband.
• Active Electrode Fabrication and Placement

• Headband
• The 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
  headbands 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.

Abstract The 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
meditations clinical potential developing a
device to enhance ones 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.
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 users ear as a
reference (Fig. 2b). A driven-right leg (DRL)
circuit is used to interface the reference
electrode with the remainder of the
amplifier circuit. 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.
Fig. 1
Fig. 2
a
a
c
b
b
d
Problem Statement To 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.
Fig. 4
Fig. 3
a
Cost Analysis Single prototype
production costs Production costs for 10,000
units 73.80 per unit
42.70 per unit
a
c
b
d
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.
b
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
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.
Future Work Multiple 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.
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.

• 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