Electroencephalography (EEG)
Examining changes in the beta- and alpha activity (EEG II)
Analysis and evaluation of the recorded data
ELUP students
Experiment was accomplished by:
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Teacher:
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Date:
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Subject’s
name: ...................................................
height: ...............................
age: ...................................................
weight: ..............................
gender: male / female
2
Aims of the practical lesson (brief definition in a few sentences)
Introduction (can be continued on a separate sheet if needed)
1. Mechanisms related to the generation of EEG, basics of the EEG
recording, typical EEG waveforms (summary of the most important facts with
regard to the analysis of the practical data)
2. Methods and materials (schematic enumeration)
3. Technical details of the practical exercises (preparation of the subject,
settings of the recording system, explanation of the exercises)
3
A. Data and calculations
After opening of the Lesson04 (EEGII) recording, the following signals can be seen on the display:
channel 1(CH1) – recorded („raw”) EEG signal; channel 40 (CH40) – alpha frequency
band (after digital filtering of the EEG signal); channel 41 (CH41) – alpha rms. Alpha rms is the
root mean square value of the signal within a window length of 0.25 seconds. This parameter
provides a good characterization for the actual quantity of the alpha waves.
Attach the printouts from the magnified, analyzed recording segments to the lab record and
note the number of the attachments.
1. Determination of the amplitude as well as frequency of alpha waves
Name a segment from the EEG recording
when you expect high alpha activity:
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Number of the segment: .....................
Analyze the signal seen on channel 1 (recorded „raw” EEG signal). Magnify the selected
section by the Zoom cursor then set the amplitude of the signal by the Display/Autoscale
Waveforms function. Use the following measurement windows: channel 1 (raw EEG) – p-p
(peak-to-peak; this measurement shows the difference between the maximum and minimum
amplitude value in the selected area); channel 1 (raw EEG) – delta T. Identify the consecutive
alpha waves. Select an alpha wave by the I-beam cursor from the beginning of the wave to the peak
of the wave. By this kind of selection, you can measure the amplitude of the wave. Then insert the
value seen in the channel 1 (raw EEG) p-p measurement window to the p-p (amplitude) line of the
table below. After that, select the same alpha wave from the beginning to the end. Period time of
the wave will appear in the channel 1 (raw EEG) – delta T measurement window. Insert this value
to the table below. (Delta time can be negative if the selection had been made in a reverse order i.e.
the end of the wave was selected first and the wave onset last). Repeat the above-mentioned
procedure to 7 different, consecutive alpha waves. Calculate frequency values from the period time
values. Calculate the mean of the amplitude-, period- as well as frequency values.
EEG waves (alpha activity)
.
mean
1.
2.
3.
4.
5.
6.
7.
8.
p-p (amplitude) [V]
delta T (period time) [s]
frequency [Hz]
Number of the attachment:..................
2. Determination of the amplitude as well as frequency of alpha waves
Name a segment from the EEG recording
when you expect high beta activity:
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Number of the segment: .....................
Analyze the signal seen on channel 1 (recorded EEG signal). Analysis should be made in
a similar way as in Exercise 1.
4
EEG waves (beta activity)
.
mean
1.
2.
3.
4.
5.
6.
7.
8.
p-p (amplitude) [V]
delta T (period time) [s]
frequency [Hz]
Number of the attachment:..................
3. Effects of different interventions on the quantity of alpha waves
Analyze the signal seen on channel 41 (alpha rms). Magnify the selected section by the Zoom
cursor then set the amplitude of the signal by the Display/Autoscale Waveforms function. Use the
following measurement window: channel 41 – mean. Take notice of the recorded EEG (channel 1)
and select a 2-seconds-long part from every recording segment. Read the alpha rms values
appearing on the measurement window and fill them into the table below.
When you select a part from the 1st (control) segment, pay attention to select a segment where
several alpha waves can be seen in the recorded EEG (channel 1). In case of the 2nd
segment (mental math), select that segment for the analysis which shows the data recorded
immediately after the order to calculate (when the subject likely shows maximal mental activity).
Take care to select artifact-free epochs. Alpha rms value of thefirst segment is the reference
(control).
Calculate alpha rms differences between control and experimental segments!
mean alpha
rms (Ch 41 mean)
[V]
control: closed eyes,
quiet state
(1st segment)
mental math
(2nd segment)
hyperventilation
(3rd segment)
eyes open
(4th segment)
alpha rms difference
compared to the
control (experimental control state) [V]
evaluation
(increase /
decrease / no
change)
Number of
the
attachment
5
4. Artifacts
Does the recording contain artifacts?
yes
no
If artifacts are present in the recording, mark them on the printouts and reference them by numbers.
Identify the types of the artifacts.
Number of the attachment(s):..................
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B. Data summary and conclusions
1. Under which condition did you observe the largest amount of alpha waves? Use the table at
Exercise3!
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2. Under which condition did you observe the smallest amount of alpha waves? Use the table at
Exercise3!
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3. How did the quantity of alpha waves change with the degree of attention?
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4. Based on the experimental results, did the subject pay attention to the mental math task?
yes
no
5. Compare the EEG patterns recorded with eyes open or closed.
a) What kind of changes did you observe in the EEG when the subject's eyes were open?
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b) What happens to the functioning of the occipital lobe neurons when the subject opens his/her
eyes?
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c) What happens to the functioning of the occipital lobe neurons when the subject closes his/her
eyes?
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d) When is beta rhythm more pronounced?
eyes open
eyes closed