LAB MANUAL

OF

ELECTROENCEPHALOGRAPHY
(EEG)












Submitted By:





Contents


1) Electroencephalography
Background of EEG
Recording EEG
Components of EEG waveform
Required Equipment

2) Power Lab
Data Acquisition
Software Used

3) Lab Tutor
Access to Lab Tutor
Perform Experiments
Equipment Setup
Exercise 1: Recognizing Artifacts
Exercise 2: Alpha And Beta Rhythms
Exercise 3: Mental Activity
Exercise 4: Auditory Stimulation

4) Lab Chart
Equipment Setup
Exercise 1: Recognizing Artifacts
Exercise 2: Alpha Waves in EEG
Spectral Analysis

5) Conclusion








1) Electroencephalography

In this experiment, we will examine an electroencephalogram (EEG) and explore the electrical
activity of the brain. We will record an electroencephalogram from a volunteer, look at
interfering signals, and examine the effects of visual activity on alpha brain waves.
Background
The cerebral cortex contains huge numbers of neurons. Activity of these neurons is to
some extent synchronized in regular firing rhythms. These are referred to as brain waves.
Electrodes placed in pairs on the scalp can pick up variations in electrical potential that
derive from this underlying cortical activity. The recording of the electrical activity is
called an electroencephalogram (EEG). EEG signals are affected by the state of arousal
of the cerebral cortex and show characteristic changes in different stages of sleep. EEG
signals are also affected by stimulation from the external environment and brain waves
can become entrained to external stimuli. Electroencephalography is used, among other
things, in the diagnosis of epilepsy and the diagnosis of brain death.

Recording the EEG
EEG recording is technically difficult, mainly because of the small size of the voltage
signals, which are typically 50 V peak-to-peak. The signals are small because the
recording electrodes are separated from the brain's surface by the scalp, the skull, and a
layer of cerebrospinal fluid. A specially designed amplifier, such as the Bio Amp built
into the Power Lab, is essential to record EEGs. It is also important to use electrodes
made of the right material and to connect them properly. Even with these precautions,
recordings may be spoiled by a range of unwanted interfering influences, known as
artifacts.
Here, we will record EEG activity with two electrodes: a frontal electrode on the
forehead, and an occipital electrode on the scalp at the back of the head. A third (ground
or earth) electrode is also attached, to reduce electrical interference. In clinical EEG, it is
usual to record many channels of activity from multiple recording electrodes placed in an
array over the head.

Components of the EEG waveform
The EEG waveform contains component waves of different frequencies. These can be
extracted and provide information about different brain activities. The types of brain
waves are:
alpha (between 8 to 13 Hz; average amplitudes of 30 to 50 V peak-to-peak)
which will be studied in this experiment. Alpha rhythm is seen when the eyes
are closed and the volunteer relaxed. It is abolished by eye opening and by
mental effort such as doing calculations or concentrating on an idea. It is thus
thought to indicate the degree of cortical activation. The greater the activation,
the lower the alpha activity. Alpha waves are strongest over the occipital (back
of the head) cortex and also over the frontal cortex.
beta (13 to 30 Hz; <20 V peak-to-peak) which are prominent in alert
individuals with their eyes open. The beta rhythm may be absent or reduced in
areas of cortical damage and can be accentuated by sedative-hypnotic drugs such
as benzodiazepines and barbiturates.
theta (4 and 8 Hz; <30 V peak-to-peak) which are seen in awake children but
not adults. The theta rhythm is normal during sleep at all ages. However, some
researchers separate this frequency band into two components, low theta (4 - 5.45
Hz) activity that they correlate with decreased arousal and increased drowsiness,
and high theta (6 - 7.45 Hz) activity that it is claimed is enhanced during tasks
involving working memory.
delta (0.5 and 4 Hz; up to 100 - 200 V peak-to-peak) which is the dominant
rhythm in sleep stages three and four but not seen in conscious adults. The delta
rhythm tends to have the highest amplitude of any of the component EEG waves.
EEG artifacts caused by movements of jaw and neck muscles can produce waves
in the same frequency band.
gamma (30 and 50 Hz). Most people recognize gamma rhythm, but its
importance is controversial. It may be associated with higher mental activity,
including perception and consciousness and it disappears under general
anesthesia. One suggestion is that the gamma rhythm reflects the mental activity
involved in integrating various aspects of an object (color, shape, movement,
etc.) to form a coherent picture.

In general, the more active the brain the higher the frequency and the lower the amplitude
of the EEG. Conversely, the more inactive the brain the lower the frequency and the
higher the amplitude of the signal.

Required Equipment
Lab Chart software
Power Lab Data Acquisition Unit
5 Lead Shielded Bio Amp Cable
EEG Flat Electrodes
Electrode Paste
Abrasive Gel or Abrasive Pad
Alcohol Swabs
Ballpoint pen
Medical tape
Elastic bandage




2) Power Lab
PowerLab (before 1998 was referred to as MacLab) is a data acquisition system developed
by AD Instruments comprising hardware and software and designed for use in life science
research and teaching applications. It is commonly used in physiology, pharmacology,
biomedical engineering, sports/exercise studies and psychophysiology laboratories to record and
analyze physiological signals from human or animal subjects or from isolated organs. The
system consists of an input device connected to a Microsoft Windows or Mac OS computer
using a USB cable and LabChart software which is supplied with the PowerLab and provides the
recording, display and analysis functions. The use of PowerLab and supplementary AD
Instruments products have been demonstrated on the Journal of visualized Experiments
.

The original MacLab unit was developed in the late 1980s to run with
only Macintosh computers to perform computer-based data acquisition and analysis. The
MacLab product range was renamed "PowerLab" in 1997 to reflect the cross-platform nature of
the system.
The PowerLab system is essentially a peripheral device designed to perform various functions
needed for data acquisition, signal conditioning and pre-processing. Versatile display options and
analysis functions are complemented by the ability to export data to other software (such as
Microsoft Excel).
How is data acquired?
External signals detected are converted into analog electrical signal.
Signals are amplified to amplify signals and filtered to remove unwanted
frequencies or noise.
Analog signal is multiplexed to an analog to digital converter.
The digitized signal is transmitted to the computer using USB connection.
Software receives, displays, analyses and records data in real time.

Software for Power Lab
LabChart
Formerly known as Chart. The software functions like a traditional multi-
channel chart recorder, XY plotter, polygraph and digital voltmeter. It is
compatible with both Windows and Macintosh operating systems. The software
has hardware settings control, performs analysis in real-time and offline without
the loss of raw data, procedure automation via editable macros, and multiple
block samplings for the recording and settings of different signals within one
file. Large specialized add-ons called Modules provide data acquisition and
analysis features for specific applications such as ECG, blood pressure, cardiac
output, HRV and etc. Smaller software plugins provides additional and
specialized functionality to LabChart. Extensions perform functions such as file
translations into other formats (including PVAN and Igor Pro) and specialist
analysis functions (for specific research areas such as spirometery and ventricular
pressure). The last version of LabChart6 (version 6.1.3) was released on January
2009.
In April 2009, LabChart 7 was released and incorporates the features of a multi-
channel digital oscilloscope that allows recording and averaging of up to sixteen
signals in real time. Latest version of LabChart7 is version 7.0.
LabTutor
Software provides a range of hands-on laboratory background for students that
includes experimental background & protocols, data acquisition & analysis, and
report generation within one interface. The software and accompanying PowerLab
hardware is configured for immediate use with step by step instructions designed
to maximize student productivity by applying independent learning techniques to
a suite of human and animal physiological experiments. Recently, LabAuthor
software was released to provide educators the ability to design or edit existing
LabTutor experiments and tailor the experiments to suit their practical classes
without the need of programming or html skills.










3) Lab Tutor


Acess LabTutor
To access LabTutor one can use the desktop shortcut created during the LabTutor Client
installation. The student login page address can also be manually typed into the web
browser using the server name or the server IP address:
http://<server IP address>
http://<computer name>
There are two modes of operation for LabTutor Client, depending on the licensing model
that is purchased:
1. Require PowerLabs Students can log in and perform experiments if the computer
on which LabTutor Client is installed has a PowerLab connected.
2. LabTutor Online mode Where LabTutor Online is activated, and a student is
licensed as such in Bulk or Student Access Card modes, they may log in and start or
continue an experiment on any computer on which LabTutor Client is installed, with or
without a PowerLab connected. LabTutor Client can be installed on any number of
computers.



Perform Experiments
In the web browser, navigate to the LabTutor student login page.
Log in using a student login.
Choose the course and experiment that you want to start.
Select experiment EEG from the Human Physiology course list.
Read the Introduction part of the experiment.



Equipment Setup
Plug the Bio-Amp cable into the Bio-Amp socket on the PowerLab.
Connect the leads of three EEG flat electrodes to Earth, CH1 NEG and POS, on
the Bio-Amp cable.



Exercise 1: Recognizing Facts

Procedure

Blinking Artifact
1. Click Start and ask the volunteer to blink repeatedly.
2. Watch the volunteer and push the enter key to enter the comment each
time the volunteer blinks.
3. After 5 to 10 seconds, click Stop.

Eye Movements
1. Click Start and ask the volunteer to gaze alternately left and then right in a
repeated pattern. The volunteer should keep the head still during these
movements.
2. Watch the volunteer and push the enter key to enter the comment each
time their eyes moves.
3. After 5 to 10 seconds, click Stop.

Head Movements
1. Click Start and ask the volunteer to move head alternately left and then
right in a repeated pattern.
2. Watch the volunteer and push the enter key to enter the comment each
time their head moves.
3. After 5 to 10 seconds, click Stop.


Analysis

Examine the recordings using scroll bar at the bottom of the LabTutor panel and
by adjusting the vertical scale.
True EEG signal rarely exceed +50V and -50V. We have to find the large
signals outside the 50V range that belong to blinking artifacts, eye movements
and head movements. These large signals are artifacts.




Exercise 2: alpha and beta rhythm
Here we examine the alpha and beta waves in the EEG and the effect of having the eyes
shut or open on this rhythm.


Procedure

Ensure that the volunteer is relaxed and is lying quietly with both eyes open.
Click Start.
Type shut in the comments panel. After about 30 seconds, ask the volunteer to
shut both the eyes. Immediately click Add to enter the comment and continue
recording.
Type open in the comments panel. After about 30 seconds, ask the volunteer to
open both the eyes. Immediately click Add to enter the comment.
Record for a few more seconds and then click Stop.
Repeat this procedure twice more to give three sets of result.



Analysis

From the first recording, for the period when the volunteers eyes were open
select a portion relatively free from artifacts.
On making a selection the four value panels will display measurements of
amplitude and frequency for both alpha and beta waves for selected period. Drag
values to appropriate cell in the table.
Repeat the same for eyes shut and for two other recordings. The table will
display average amplitude and frequency along with the standard deviation.
Once completed use the navigation buttons below the table to view a graph of
these variables.







Exercise 3: Mental Activity
Here we examine the effect of mental arithmetic task on alpha and beta rhythm, while the
eyes are closed.


Procedure

Ensure that the volunteer is relaxed and is lying quietly with both eyes closed.
Click Start.
Enter the comment shut in the comments panel. After about 30 seconds of
sustained alpha rhythm give the volunteer some instructions regarding some easy
arithmetic calculation. Instruct to merely think the response and not to speak it.
Add the comment math when you instruct to start the mental arithmetic.
After another 30 seconds instruct the volunteer to stop calculating and to relax.
Record for a few more seconds and then click Stop.
Repeat the procedure for further sets of recording.



Analysis

From the first recording, for the period when the volunteers eyes were shut but
they werent perform any mental arithmetic.
Drag the calculated measurements of amplitude and frequency from the value
panels to appropriate cell in the table.
Repeat the same for eyes shut with and without arithmetic for two other
recordings. The table will display average amplitude and frequency along with the
standard deviation.
Once completed use the navigation buttons below the table to view a graph of
these variables.






Exercise 4: Auditory Stimulation
Here we examine the effect of different types and volumes of music on alpha and beta
rhythm, with the eyes closed.


Procedure

Well need a set of headphones and a method of playing music to a subject.
Cue the following types of music for presentation to the volunteer:
o Soothing (classical) music, volume low
o Soothing (classical) music, volume high
o English (Rock) music, volume low
o English (Rock) music, volume high
Ensure that the volunteer is relaxed and is lying quietly with headphones on and
the both eyes closed.
Click Start.
Enter the comment shut in the comments panel. After about 30 seconds of
sustained alpha rhythm present the first type of music and add an appropriate
comment.
After another 30 seconds of recording stop the music.
Record for a few more seconds and then click Stop.
Repeat this procedure for each different type and volume of music.







Analysis

From the first recording, for the period when the volunteers eyes were shut with
no music playing.
Drag the calculated measurements of amplitude and frequency from the value
panels to appropriate cell in the table.
Repeat the same for eyes shut with and without the different types of music for
two other recordings. The table will display average amplitude and frequency.
Once completed use the navigation buttons below the table to view a graph of
these variables.








At the end one can submit the report by giving the answers to various question given. Also one
can print the pdf file of the report.










4) Lab Chart

Equipment Setup and Electrode Attachment
1. Make sure the Power Lab is turned off and the USB cable is connected to
the computer.
2. Connect the 5 Lead Shielded Bio Amp Cable to the Bio Amp Connector
on the front panel of the Power Lab (Figure 1). The hardware needs to be
connected before you open the settings file.
3. Attach the leads of the EEG Flat Electrodes to the Earth, CH1 NEG and
POS pins closest to the labeled side on the Bio Amp Cable. Channel 1
positive will lead to the inion (the bump on the back of the head above
the neck) and Channel 1 negative will lead to the forehead. Channel 2
will be empty and the Earth will lead to the temple.
4. Remove any jewelry from the volunteers face, ears, and neck. Use a
ballpoint pen to mark a small cross on the skin on the back of the head,
forehead, and temple. Use Figure 1 as a guide.
5. Abrade the skin with Abrasive Gel or Pad. This is important as abrasion
helps reduce the skins resistance.
6. After abrasion, clean the area with an alcohol swab to remove the dead
skin cells. While the skin is drying, scoop Electrode Paste into the EEG
Flat Electrodes. When the skin is dry stick the electrodes to the skin
(Figure 1). Immediately hold the electrodes and wires in place with the
medical tape.
7. Make sure the tape firmly holds the electrodes against the head. Use the
elastic bandage to wrap tightly around the head. This will help the
electrodes maintain good contact with the skin. The volunteer should lie
in a comfortable position on their back, with their head turned so that none
of the electrodes are disturbed or compressed.
8. Check that all three electrodes are properly connected to the volunteer and
the Bio Amp Cable before proceeding. Turn on the Power Lab.


Figure 1. Equipment Setup for PowerLab 26T


Exercise 1: Recognizing Artifacts
To examine some of the artifacts that can contaminate an EEG record.
Procedure
1. Launch Lab Chart and open the settings file EEG Settings from the
Experiments tab in the Welcome Center. It will be located in the folder
for this experiment.



2. Select Bio Amp from the EEG Channel Function pop-up menu. It should
be the only channel visible. Make sure the settings are as follows: Range
200 V, High Pass 0.5 Hz, and Low Pass 50 Hz.


Figure 2. Bio Amp Dialog
3. Start recording. Add a comment blinking, and have the volunteer blink
repeatedly. Stop recording after 10 seconds.
4. Repeat step 3, this time, have the volunteer make eye movements. Add a
comment eye movements. Have the volunteer gaze up-and-down and
left-and-right in a repeated pattern. Make sure the volunteers head is still
and only the eyes move.
5. Repeat step 3, this time, have the volunteer make head movements. Add a
comment head movements. Have the volunteer gently move his/her
head in a repeated pattern.
6. Save your data, and open a new file with the same settings.



Exercise 2: Alpha Waves in the EEG
To examine alpha waves (alpha rhythm) in the EEG, and the effect of opening the eyes.
Procedure
1. Make sure the volunteer is relaxed and comfortable. Have the volunteer
close his/her eyes and remain quiet. Keep noise to a minimum and keep
all distractions away from the volunteer.
2. Start recording. Record for 30 seconds. Prepare a comment with open;
do not enter it yet. Tell the volunteer to open both eyes. Immediately
press Return/Enter to add the comment.
3. Record with the volunteers eyes open for 10 seconds. Do not stop
recording.
4. Prepare a comment with shut. When the 10 seconds are complete, tell
the volunteer to close both eyes. Immediately press Return/Enter to add
the comment.
5. Repeat steps 3 and 4 twice, to give you three sets of results. Save your
data.


Analysis
Exercise 1: Recognizing Artifacts
1. Examine the vertical scale at the left of the Chart View, and note the
positions corresponding to +50 V and 50 V. True EEG signals rarely
exceed these limits.
2. Examine the entire data trace and Autoscale, if necessary. There may be
some large signals outside the 75 V range. Such large signals are
artifacts.



Exercise 2: Alpha Waves in the EEG
1. Examine the entire data trace. Use the View Buttons to change the
horizontal compression to see data with eyes open and shut. Make a data
selection that includes some data from both eyes open and eyes shut
conditions. View this selection in Zoom View. This should make it easier
to see the alpha wave activity (Figure 3). Now Autoscale, if necessary.

Figure 3. EEG signal with eyes shut and open. Note alpha waves during eyes shut.
2. In Chart View scroll through the parts of the recording that were made
with the volunteers eyes shut to look for alpha waves. Use the View
Buttons to change the horizontal compression if necessary. The alpha
waves can be recognized by their amplitude (usually 30 to 50 V peak-to-
peak, although it can be quite variable) and their frequency. Each cycle of
an alpha wave should last approximately 0.1 s.
3. Use the Marker and Waveform Cursor to measure the amplitude of the
alpha waves. Place the Marker at the lowest point of the wave and move
the Waveform Cursor to the peak of the wave. Measure the amplitudes
of five waves from when the volunteers eyes were closed. Record the
values in Table 1 of the Data Notebook.
4. Now measure wave amplitudes when the volunteers eyes were open.
Record these values in Table 2 of the Data Notebook.

The amplitude of the waves is affected by the quality of the EEG signal. Therefore, it is
useful to examine the frequency and power of the wave activity. Spectral analysis can be
used to examine these features of a signal. Before examining your EEG signal you will
complete a short tutorial on Spectral Analysis.

Spectral Analysis
A spectrum is a representation of data based on the frequency distribution of its
component sine waves. Spectra indicate the strength of the various frequencies in a time-
varying waveform. Spectrum View allows you to observe the frequency distribution of
data that might not otherwise be easily seen. For example, it could be used to break down
an EEG waveform into its various components: beta waves, alpha waves, theta waves and
delta waves. A mathematical technique known as the Fast Fourier Transform is applied to
the raw data. The results of this analysis can be displayed as a plot of the power (vertical
axis) of different frequencies (horizontal axis) relative to each other in the input signal.
This is called a Power Spectrum Density (PSD) plot. The data can also be displayed as 3-
dimensional color plot of spectral power, frequency, and time called a Spectrogram.
Open the Welcome Center and in the Experiments tab browse the EEG
Spectral Analysis Tutorial. It will be in the Settings folder for this experiment.
Open this file.
Examine the Chart View. Use the View Buttons to view each block. You should
see five blocks of data. The first record is a slowly oscillating sine wave.
Open Spectrum view by clicking on the Spectrum View button in the Toolbar
(Figure 4).

Figure 4. Spectrum View Toolbar button
A. Click the Smart Tile button in the LabChart Toolbar to display both windows in full screen
mode.
B. In Chart View Select the first record by double clicking in the Time axis. This will perform
a spectral analysis for this record and displays the result in the Spectrum view. Adjust the
horizontal scaling of plots to view the results:
Set the horizontal scaling for the Power Spectrum Density (PSD) plot to 50 Hz
(Figure 5). Use the horizontal scroll bar to display the 0 Hz to 50 Hz region of the
plot.


Figure 5. Spectrum PSD Scale
Set the horizontal scaling for the Spectrogram to 50:1.
Examine the PSD plot and then the first section of the Spectrogram. Expand the vertical axes if
necessary. Use the waveform cursor to identify the frequency in Hertz (Hz) of the peak in the
PSD plot and the band in the Spectrogram. Values are displayed at the top of each plot.

1. Use the View Buttons to change the horizontal compression to 10:1 (Figure 7).
2. Find the part of the recording when the volunteer had his/her eyes shut. Click-and-drag
across this part of the data trace to select it. From the Window menu, select Spectrum. In
the Spectrum View choose Selected (Figure 8).

3. Find the part of the recording when the volunteer had his/her eyes shut. Click-and-drag
across this part of the data trace to select it. From the Window menu, select Spectrum. In
the Spectrum View choose Selected (Figure 8).


Figure 7. Alpha Waves with 10:1 Compression

4. Find the part of the recording when the volunteer had his/her eyes shut. Click-and-drag
across this part of the data trace to select it. From the Window menu, select Spectrum. In
the Spectrum View choose Selected (Figure 8).

Figure 8. Spectrum of an EEG

5. Alpha activity shows up in the PSD plot as a clear peak in the 8-12 Hz range. Then print the
PSD plot.
6. Alpha activity shows up in the Spectrogram as a band of color in the 8-12 Hz range. If you
cannot see the alpha activity as a clear peak in the 8-12 Hz range, scale the horizontal and
vertical axes. Note that Spectrogram displays all the recorded data and that the selection you
have made is highlighted in a darker blue color.
7. Make a data selection of several seconds from when the volunteer had their eyes open.
Select Spectrum. Note that in the PSD plot the peak in the alpha activity range of 8-12 Hz is
small or absent and in the Spectrogram the band of color in the alpha activity range of 8-12
Hz is weak or absent. Print the PSD plot.
8. In the Spectrogram scale the horizontal axis so that all the data is visible. Note the presence
and absence of the band of color in the alpha activity range of 8-12 Hz which correspond
with the eyes shut and eyes open conditions. Print the Spectrogram.




















5) Conclusion

Here we analyzed that the alpha and beta rhythms are affected by different parameters like eyes
shut, eyes open, arithmetic calculation, various types of music etc.
When eyes are open, the alpha amplitude of the wave is very much low than the
amplitude in case of closed eyes.
When eyes are open, the beta amplitude of the wave is low than the amplitude in case of
closed eyes but the difference between the two cases are less as compared to alpha wave
amplitude.
When eyes are open, the alpha frequency of the wave is higher than the frequency in case
of closed eyes.
There is very slight difference in the beta frequencies in both the cases.
The amplitude of alpha wave is more without arithmetic than with arithmetic. As with
arithmetic the subject has to do some mental exercise.
There is very less variation in the frequencies both alpha and beta frequency.
Also there is not much variation in the beta amplitude with and without arithmetic.
There is a visible change in the amplitudes of wave (alpha and beta both) as the music is
presented to a subject. This is so because the subject is not familiar to the music, but as
the subject becomes familiar and starts enjoying the music then the difference between
the amplitude starts improving.
No doubt there is change in frequency, but change in frequencies is not that large.