LAB MANUALOF

ELECTROENCEPHALOGRAPHY

Contents

• Electroencephalography

• Required Equipment

• Power Lab

• Lab Tutor

• Lab Chart

• Conclusion

Contents

• Electroencephalography

• Required Equipment

• Power Lab

• Lab Tutor

• Lab Chart

• Conclusion

Electroencephalography (EEG)

• 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.

EEG in the States of Vigilance

Frequency Ranges of Heart Rhythms:

Beta: 13 – 30 Hz

Alpha: 8 – 13 Hz

Theta: 4 – 8 Hz

Delta: 0.5 – 4 Hz

Contd…

Alpha RhythmFrequency: 8 – 13 Hz

Amplitude: 30 – 50 microVolt peak-to-peak

Location: Occipital, Parietal

State of Mind: Alert Restfulness

Alpha blockade occurs when

new stimulus is processed.

Source: oscillating thalamic

pacemaker neurons

Beta RhythmFrequency: 13 – 30 Hz

Amplitude: <20 microVolt peak-to-peak

Location: Frontal

State of Mind: Mental Activity

Reflects specific information

processing between cortex and

Thalamus.

Theta RhythmFrequency: 4 – 8 Hz

Amplitude: <30 microVolt peak-to-peak

Location: Frontal, Temporal

State of Mind: Sleepiness

Nucleus reticularis slows oscillating

thalamic neurons.Therefore

diminished sensory throughput

to cortex.

Delta Rhythm

Frequency: 0.5 – 4 Hz

Amplitude: 100 – 200 microVolt peak-to-peak

Location: Variable

State of Mind: Deep sleep

Oscillations in Thalamus and deep cortical

Layers. Usually inibited by ARAS

(Ascending Reticular Activation System)

Contents

• Electroencephalography

• Required Equipment

• Power Lab

• Lab Tutor

• Lab Chart

• Conclusion

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

Contents

• Electroencephalography

• Required Equipment

• Power Lab

• Lab Tutor

• Lab Chart

• Conclusion

Power Lab

It 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.

Contd…

Software used:

o Lab Tutor

o Lab Chart

Contents

• Electroencephalography

• Required Equipment

• Power Lab

• Lab Tutor

• Lab Chart

• Conclusion

Lab Tutor

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.

Contd…

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 ArtifactsBlinking Artifact

• Click Start and ask the volunteer to blink repeatedly.

• Watch the volunteer and push the enter key to enter the comment each time the volunteer blinks. After 5 to 10 seconds, click Stop.

Eye Movements

• 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.

• Watch the volunteer and push the enter key to enter the comment each time their eyes moves. After 5 to 10 seconds, click Stop.

Contd…

Head Movements

• Click Start and ask the volunteer to move head alternately left and then right in a repeated pattern.

• Watch the volunteer and push the enter key to enter the comment each time their head moves.

• After 5 to 10 seconds, click Stop.

Contd…

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 +50µV and -50µV. We have to find the large signals outside the ±50µV range that belong to blinking artifacts, eye movements and head movements. These large signals are artifacts.

Exercise 2: alpha and beta rhythm

• 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.

Contd…

Analysis

• From the first recording, for the period when the volunteer’s 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.

Contd…

Exercise 3: Mental Activity

• 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.

Contd…

Analysis

• From the first recording, for the period when the volunteer’s eyes were shut but they weren’t 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.

Contd…

Exercise 3: Auditory Stimulation

• We’ll 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:

Soothing (classical) music, volume low

Soothing (classical) music, volume high

English (Rock) music, volume low

English (Rock) music, volume high

• Ensure that the volunteer is relaxed and is lying quietly with headphones on and the both eyes closed.

Contd…

• 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.

Contd…

Analysis

• From the first recording, for the period when the volunteer’s 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.

Contd…

Contents

• Electroencephalography

• Required Equipment

• Power Lab

• Lab Tutor

• Lab Chart

• Conclusion

Lab Chart

Formerly known as Chart. The software functions like a traditional multi-channel chart recorder, XY plotter, polygraph and digital voltmeter. 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. 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.

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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 Artifacts• 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.

• 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 µV, High Pass 0.5 Hz, and Low Pass 50 Hz.

• Start recording. Add a comment “blinking,” and have the volunteer blink repeatedly. Stop recording after 10 seconds.

• 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 volunteer’s head is still and only the eyes move.

Contd…

• 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.

• Save your data, and open a new file with the same settings.

Contd…

Analysis

• Examine the vertical scale at the left of the Chart View, and note the positions corresponding to +50 µV and –50 µV. True EEG signals rarely exceed these limits.

• Examine the entire data trace and Autoscale, if necessary. There may be some large signals outside the ±75 µV range. Such large signals are artifacts.

Exercise 2: Alpha Waves in the EEG

• 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.

• 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.

• Record with the volunteer’s eyes open for 10 seconds. Do not stop recording.

• 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.

• Repeat steps 3 and 4 twice, to give you three sets of results. Save your data.

Contd…

Analysis

• 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. Now Autoscale, if necessary.

• In Chart View scroll through the parts of the recording that were made with the volunteer’s 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 µV peak-to-peak, although it can be quite variable) and their frequency. Each cycle of an alpha wave should last approximately 0.1 s.

Contd…

Analysis

• 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 volunteer’s eyes were closed. Record the values in Table 1 of the Data Notebook.

• Now measure wave amplitudes when the volunteer’s eyes were open. Record these values in Table 2 of the Data Notebook.

Spectral Analysis

• 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

Contd…• Click the Smart Tile button in the LabChart Toolbar to display both windows in full

screen mode.

• 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. Use the horizontal scroll bar to display the 0 Hz to 50 Hz region of the plot.

• Set the horizontal scaling for the Spectrogram to 50:1.

Contents

• Electroencephalography

• Required Equipment

• Power Lab

• Lab Tutor

• Lab Chart

• Conclusion

Conclusion• 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.

Contd…

• 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.