1. Da’Janel Roberts Matthew Morgan Jonathan James
Neural Design Group N2
Da’Janel Roberts
Matthew Morgan
Jonathan James

2. Goals Research EEG theory Replicate Brainmaster amplifier design.
Determine whether the Brainmaster design can actually measure brainwaves.

3. What is a brain wave?
The sum of the electrical activity of millions of neurons, located primarily in the cortex.
Measured by an electroencephalogram (EEG) via surface electrodes.
Classified according to three properties:
Frequency
Amplitude
Shape

4. International 10/20 System of Electrode Placement
                                                                    
Most widely used method.
Electrodes are placed relative to the underlying area of cerebral cortex.
Letters correspond to brain lobe area.
The "10" and "20" refer to the 10% and 20% interelectrode distance. 

5. Types of Brain Waves Five types of brain waves Alpha Beta Theta DeltaMu

6. Alpha Waves
8 – 13 Hertz
Low amplitude
Relaxation
Reflecting
                                     

7. Beta Waves 14 – 30 Hertz Rapid oscillations with small amplitudes
Alertness
Working

8. Theta Waves 4 – 7 Hertz Prominent when dreaming or drowsy.
Arise from emotional stress such as frustration.

9. Delta Waves Less than 3.5 Hertz
Occur during deep sleep or other non-attentive states of mind
Prominent when totally subconscious

10. Mu Waves Resemble croquet wickets in shape
Associated with physical movements or the intentions to move.

11. EEG Amplifier Requirements
High Gain (80dB and up)
Low Noise
Bandwidth (.5Hz to 50Hz)
Minimal cost

12. Current Technologies Various technologies available: WaveRider Series
Mindset
BrainMaster

13. WaveRider Series WaveRider Pro, 4 channels, $1700.
WaveRider Jr., 2 channels, $950.
CEO, 1 channel, $545.
Pro version monitors brain waves (EEG), heart rate, muscle tension (EMG), and skin resistance (GSR).
.5 Hz – 40 Hz pass band, -72 db at 60 Hz.
8 bit A/D converter, 128 samples-per-second.

14. Mindset Mindset, 16 channels, $2195-$4999.
Different software sets: one for research and one for clinical use.
Uses 2 fourth-order Sallen-key active filters, 48db roll-off per octave, 1.8 Hz - 36 Hz frequency pass band.
16 bit A/D converter, 1024 samples-per-second-per-channel (programmable from 64).

15. BrainMaster The BrainMaster was the design we decided to replicate.
Specifications:
Gain : 20,000 (86dB)
Bandwidth : 1.7Hz – 34Hz
CMRR : 100dB

16. BrainMaster schematic
The AD620 is an integrated instrumentation amplifier made by Analog
Devices. It is an extremely high quality device --- good price
The amplifier IC-2 is used to provide an integrator, used as a
low-pass filter developing the reference for IC-1.
1st stage - This results in a
baseline-correction that produces a low-frequency cutoff at 1.6 Hz.
It also allows the output of IC-1 to operate near its center, providing
good linearity. The input amplifier IC-1 is an Analog Devices AD620 instrumentation
amplifier, set up with a gain of 50
2nd stage - The second stage provides a gain of 390 and a frequency response to
34 Hz. R10 is where to select
the gain you want, or to put a potentiometer for adjustable gain.
To apply this circuit, you need three (3) body connections, to get one
channel. Two of the electrodes are the inputs: one is "active", or
Grid 1, and the is "indifferent," or Grid 2. These would be somewhere
on the head, where you want to record from. They would tend to be on one
side of the head, and be considered a pair. The amplifier is creating
a differential reading between them, with a gain of 10,000. Any signal
that is common to them, is "bucked out" by the common-mode rejection
ratio, which will be near 100dB.
The third lead is the "ground return," and can be on the forehead, an
earlobe, or even another part of the body. You could also test the
amplifier by trying to get your heartbeat (EKG) recorded from one hand
to another, for example, too. However, if this lead touches "real"
ground, e.g. a waterpipe, the circuit will fail to operate, since
the AGND level will be "shorted" to ground.

17. Assembling Design
Ordering parts: Adrian Smith from group N1 ordered the parts for the design.
Difficulties with the OP-90
-Only available in surface mount.
-Adrian had to order adapters.
All parts arrived by March 15, 2002.

18. Replicating Design
Board completed the day after all the parts arrived.

19. Testing the BrainMaster
Initial inconsistencies:
-Sometimes the amplifier worked, and sometimes it didn’t.
-The problem turned out to be bad solder joints.
-The amplifier output became consistent after re-soldering the faulty joints.

20. Eyebrow Test
The electrodes were placed on the forehead high above the right eyebrow.
When the eyebrows were lifted and held up, the amplitude of the signal changed dramatically.

21. Frequency Content
When the eyebrows were relaxed, the FFT of the output of the amplifier revealed a peak at 20 Hz. This could possibly correspond to a beta wave.

22. Noise Problems? Noise was generated by physically moving wires.
Also, there was some noise in the frequency response when the electrodes were shorted together.

23. Matlab Processing
Matlab was used to clean up the noise in the signal so that we could better analyze it for brainwaves.

24. Matlab FFT Analysis
The Matlab FFT analysis did not prove the existence of brainwaves.
The 20 Hz peak present in the oscilloscope FFT capture was not present in the Matlab analysis.

25. Analysis
The output from the amplifier was not different for an aware subject and a tired subject.
If we were reading brainwaves, there should have been a visible change in the frequency analysis.

26. Conclusions
Energy exists at expected frequencies but data is insufficient to conclude it was due to brain waves.
Device could not be used as for EEG control.