Generation of EEG signals using EEG simulator

Aim

To simulate ECG signal and analyze the signal parameters.

Apparatus Required:

1. EEG Simulator
2. EEG Amplifier
3. Digital storage oscilloscope
4. connecting cables

Procedure:

1. Connect the EEG Simulator to main
2. Connect the simulator output to eeg amplifier
3. Connect the EEG amplifier to DSO.
4. Switch ON the Units
5. Put the DSO on storage mode
6. Put the switch on DC mode
7. Time / Div Knob on the mS & S division
8. Voltage /Div Knob on the 5MV
9. Now vary the amplitude as per requirement
10. If any noise on DSO, Check the ground

Theory:

Electroencephalography (EEG) is the recording of electrical activity along the scalp produced by the firing of neurons within the brain. In conventional scalp EEG, the recording is obtained by placing electrodes on the scalp with a conductive gel or paste. Electrode locations and names are specified by the International 10–20 system for most clinical and research applications. Each electrode is connected to one input of a differential amplifier (one amplifier per pair of electrodes); a common system reference electrode is connected to the other input of each differential amplifier. These amplifiers amplify the voltage between the active electrode and the reference.

A typical adult human EEG signal is about 10μV to 100 μV in amplitude when measured from the scalp and is about 10-20 mV when measured from subdural electrodes.

EEG wave patterns:

Delta wave:

Delta is the frequency range up to 4 Hz. It tends to be the highest in amplitude and the slowest waves. It is seen normally in adults in slow wave sleep. It is also seen normally in babies.

Theta wave:

Theta is the frequency range from 4 Hz to 7 Hz. Theta is seen normally in young children. It may be seen in drowsiness or arousal in older children and adults; it can also be seen in meditation.

Alpha wave:

Alpha is the frequency range from 8 Hz to 12 Hz. Hans Berger named the first rhythmic EEG activity he saw, the "alpha wave. It emerges with closing of the eyes and with relaxation, and attenuates with eye opening or mental exertion. The posterior basic rhythm is actually slower than 8 Hz in young children.

Beta wave:

Beta is the frequency range from 12 Hz to about 30 Hz Beta activity is closely linked to motor behaviour and is generally attenuated during active movements. It is the dominant rhythm in patients who are alert or anxious or who have their eyes open. Since an EEG voltage signal represents a difference between the voltages at two electrodes, the display of the EEG for the reading encephalographer may be set up in one of several ways. The representation of the EEG channels is referred to as a montage.

Tabular Column

Result:

Thus the EEG waves are studied and the amplitude and time for each waveforms are noted for a Subject.