Materials and Apparatus

GROUP NUMBER T4

PROJECT TITLE: FRESHMAN LAB PHYSIOLOGY EXPERIMENT

FOR EEG MEASUREMENT

DATE SUBMITTED: 21st December 2001

ROLE ASSIGNMENTS

ROLE GROUP MEMBER

FACILITATOR………………………..…..………Adam Furman

TIME & TASK KEEPER………………………….Anupam Gupta

SCRIBE……………………………………..……..Phil Matsunaga

PRESENTER………………………………………Cyrille Fleury

SUMMARY OF PROJECT

A freshman experiment was drawn up, and subsequently revised after evaluation by authentic freshman. Electrode placement was reconfigured from the directions given in the BioPac® manual successfully to allow for easier placement, with equal effectiveness. The freshman exceeded our expectations in their ability to understand the basic science and perform the lab. They also provided very useful insight for modifying the lab. After these suggestions were taken into consideration, the lab manual and worksheet were revised accordingly.

Objectives:

The objective of this experiment was to design a freshman laboratory experiment involving the study of electroencephalogram (EEG) recordings. Included in this design was the development of background material that would provide simple explanations of concepts used in the experiment. Furthermore, worksheets were made to guide the freshman through their experiment. Lastly, freshman subjects were given the experiment as a trial, and the effectiveness of the experiment was evaluated.

The specific aims of the experiment:

To determine optimal placement of electrodes and minimum time intervals of eyes open and closed
To create a file using BioPac® Pro for the freshman to use to run the experiment
To create an MS Excel worksheet that includes a macro for ‘t-test comparison’
To create various questions for the worksheet

There were objectives for the freshman, although the freshman were not told of these objectives, but rather prompted with a simple challenge. This challenge was:

Prove that there is a significant difference in brain activity between having eyes open and eyes closed

The objectives that the freshman were seeking in actuality were to gain exposure to the BioPac® student lab program, to learn and understand basic EEG principles, and to learn a small amount of basic statistical analysis.

The specific aims for the freshman (these were not shown to the freshman):

To learn how to setup the software and the actual experiment
To perform a minimum of four trials per subject
To study alpha brain wave function
To understand how t-tests are useful as a statistical tool

Background:

The electroencephalogram (EEG) is a representation of the electrical activity in the cerebral cortex. The cerebral cortex is the outer layer of gray matter which envelops the cerebral hemispheres. It is largely responsible for the higher brain functions, such as thought, reasoning, memory, sensation, and voluntary muscle movement. As a result, thinking or moving one’s eyes can alter the EEG readings. In this experiment, you will be studying brainwaves while the eyes are open and closed.

EEG measurements can be made by placing 3 electrodes on strategic locations on the head. The black lead is the ground connection which is theoretically at 0 Volts. Thus, it acts as the baseline for the red and white electrode measurements. Voltage measurements are taken at regions marked by the other two electrodes, and the voltage difference between these two points represents the magnitude of the raw EEG.

Out of the raw EEG, certain distinct rhythms can be filtered out. The alpha rhythm is the prominent EEG wave pattern of an individual who is awake but relaxed. These rhythms are most prominent on the occipital and parietal regions of the cerebral cortex. In this experiment, you will be studying the occipital lobe.

Regarding the eyes open/closed procedure, other lab groups this semester have found a significant difference in alpha waves. For example, group M5 found that “when the relaxed subject’s eyes are open, the amplitude of the alpha waves is significantly lower than that when the eyes are closed.” The Biopac student lesson 4 confirms that the amplitudes of alpha waves will decrease when a subject’s eyes are open. This pattern observed in the waves is referred to as desynchronization. One can see further evidence on page 255 of Berne and Levy, Physiology 4th Edition. They also agree that a difference in EEG patterns should be observed, which supports M5’s results.

Materials:

BioPac® Pro and Student Programs
Freshman
Switch

Methods:

In the first week, the optimal placement of the electrodes was determined, which would allow them to be affixed directly to the skin without the use of a very uncomfortable rubber swim cap. This allowed the electrodes to be placed in locations where they would not move. Electrodes placed on the top of the head adhered poorly because of hair. The first electrode was placed on the ear lobe for the ground which was connected to the black lead. The second electrode was placed on the temple next to the eyebrow (adjacent to the hairline) and the third electrode was placed behind the ear (in the triangle formed by the ear and the hairline). These two were connected to the white and red leads, respectively. The minimum time interval for which standard deviation values could easily be measured was determined.

In the second week the background, procedural protocol, and worksheet for the freshman lab were created. In addition, the template on the BioPac® Pro Program was constructed as well as the MS Excel® template for t-test comparison.

In the third week, a pair of BE freshmen performed the experiment well within the allotted time thereby exceeding our expectations. Afterwards, the freshman analysis of the experiment was noted and changes were subsequently made.

Results:

Initially, the optimal placement of electrodes was determined to allow for comfort and ease of placement. Instead of placing the electrodes in the hair and then placing the skull cap on top which caused a great deal of pain and discomfort and allowed for the electrode placement most likely to be altered, it was determined that a new electrode placement procedure must be determined. After various placement schemes, it was determined that the new placement of the electrode scheme would be as follows: the first electrode (black) was placed on the ear lobe for the ground, the second electrode (white) was placed on the temple next to the eyebrow and the third electrode (red) was placed behind the ear. Additional, it was determined that the time interval for keeping the eyes open and closed was 5 seconds instead of 10 seconds because after 5 seconds it became difficult to keep the eyes open and relaxed. Also, it was found that the eyes would have to be fixed in one position when open because any movement would cause a change in the EEG readings because the muscle movement would contribute to a significant change in the EEG reading.

The initial procedural protocol and worksheet were drawn up for the freshman one week before the freshman actually performed the lab. In the procedural protocol, the challenge that was presented to the freshman was simplistic. Furthermore, the background information that was provided was a very basic understanding of EEG and its relationship to the cerebral cortex with no mention of the alpha brain wave and what it is. In addition, a brief yet simplified explanation of t-tests was included that stated there exists a difference between two sets of data if the value of t-stat is less than t-critical. Finally, the actual “Lab Protocol” consisted of a detailed explanation of each step that must be completed to obtain appropriate data measurements. The worksheet asked a few basic questions about whether or not a difference occurred between open and closed eyes both graphically and analytically, by using t-tests. For the t-tests, it was agreed upon to use a macro in MS Excel because it would allow the freshman to be exposed to t-test at a rudimentary level without them actually having to do the t-test manually in Excel by using the ‘Data Analysis” function.

The two freshmen that were recruited for the experiment exceeded our expectations. They followed the protocol exactly as stated and the results were satisfactory in that there was a difference in EEG values for closed and open eyes. The freshmen seemed not to have any major difficulties in completing the experiment aside from an occasional question or not that just required more clarification of the procedure on our part.

Analysis:

After the experiment was completed, we discussed with the freshman about any modifications that are needed to be made to the procedural protocol and worksheet. After taking the freshman suggestions into consideration, the freshman experiment documents were modified. These changes resulted in a more detailed explanation of the alpha wave should be given and why there is a change in its amplitude when the eyes are open and closed, the t-test explanation should be moved to the worksheet, the procedural protocol should be put into more steps and more explanation is necessary in the use of the switch, reasoning as to why the electrodes are placed as the specific locations listed, and removal of the t-test macro and how to manually perform the t-test in MS Excel.

In order to prepare suitable background information, we sifted through Berne & Levy for information on alpha waves. We read through the BioPac® tutorial to figure out why the electrodes were placed as such. Very little of the information, however, went much beyond what we were already expected know.

The hardest part of the experiment turned out to be the availability of freshman to evaluate our procedure. Once the freshmen were in place, everything else could be planned around that date. Thus, we had the luxury of two weeks of planning. The instructions given to us at the beginning of this project were clear enough for us to outline our goals for each week without any trouble.

Not a suitable 309-project because as a 3rd semester bioengineering lab intended for juniors, projects with a great emphasis on ‘hard’ science and numerical calculations would probably prove to teach more. This project focused more on the basic concepts, which while an important aspect to research, should be supported by finer details, calculations, and statistics.

Conclusion:

Electrode placement was reconfigured successfully to allow for easier placement, with equal effectiveness.
The freshman exceeded our expectations in their ability to understand the basic science and perform the lab. They also provided very useful insight for modifying the lab.

Appendix follows this section. In the appendix, the original and revised lab manual and worksheet

Bioengineering Lab I For Freshmen

Physiology Experiment For EEG Measurement

Challenge:

Prove that there is significance difference in brain activity between having open eyes and closed eyes.

Background:

T-tests can be used to determine whether two sets of data are “the same” or “different.” When performing t-tests, one obtains a t-stat and a t-critical value. If the magnitude of the t-stat is less than the t-critical, then the two sets of numbers are not significantly different. One must take care to use the t-critical two-tailvalue, which is a less optimistic probability than the one-tail.

Materials and Apparatus:

BioPac® Acquisition Unit (MP30)

BioPac® disposable vinyl electrodes (EL 503), 3 electrodes per subject

BioPac® Electrode Lead Set

BioPac® Pro Software

Computer

Worksheet, Excel template, t-test template, background information

Noise Canceling Headphones

Switch

Lab Protocol:

Place the 3 electrodes on the same right side of the head: one on the ear lobe, the second one on the temple next to the eyebrow (adjacent to the hair line), and the third behind the ear (in the triangle formed by the ear and hair line). Wait five minutes for the gel to adhere.
On the test subject, connect the leads to the electrodes (black on the ear lobe, white on the temple, and red behind the ear) and have the subject recline on the cot. Set the headphones to block out background noise.
When subject 1 is completely relaxed, the Biopac program will be started. To start the program, click on “start” and when prompted to overwrite data, click yes. The program will then begin recording data. The subject will close their eyes for the first 5 seconds, then open them for the next 5 seconds. This will be repeated 3 more times for a total of 40 seconds worth of data. One must avoid both eye movement and blinking when the eyes are open, as any movement will have a huge impact on results. The data recorder will use a stopwatch to time the subject, and will let the subject know when it is time to open/close his eyes (a gentle tap on the shoulder is recommended). In addition to this, the recorder will use the ‘switch’ to indicate when the subject opened or closed his eyes.
When the process is completed, go to File and Save As. Save the file in the User D: and call it subject 1 data.
Repeat steps 3 and 4 for subject 2.
Finally, follow the directions on the worksheet.

Names:

Date:

‘Alpha Wave’ worksheet

Complete the following:

Open the data file for subject 1. Looking at the ‘Alpha Wave’ data (the bottom window), do you see an obvious change in the amplitude of the brain waves between the closed and open eye intervals? What about for subject 2?

Next, check to see if the average amplitudes really do change. To measure the average amplitude, first click on the I-bar cursor in the lower right part of the screen. Highlight the data between time 0 and the first switch mark. Record the “stddev” value in the table below (Open-1). Do the same for the data between the first and second switch marks. Record this as well (Closed-1). Repeat for the rest of the data (Open-2, Closed-2, Open-3, etc), and also for subject 2.

Once the table is filed out, copy the table to the Excel template, which is also located in Use D:\T4 Stuff. For each subject, perform a t-test on the amplitude values and record the t-stat and t-critical values in the table below. To perform this test, simply click the “T-test comparison” button on your excel worksheet. This will run Excel’s t-test data analysis, and give you a result of “significantly different” or “statistically the same.” Record the t-stat and t-critical in the table as well.

Subject 1 / Subject 2
Trial / Closed / Open / Trial / Closed / Open
1 / 1
2 / 2
3 / 3
4 / 4
t-stat / t-stat
t-critical / t-critical

Noting the t-stat and t-critical values for each subject, was there indeed a statistically significant change in the amplitude of the ‘Alpha Waves’ between the closed and open eye intervals? Is this what you expected?

Names:

Bioengineering Lab I For Freshmen

Physiology Experiment For EEG Measurement

Challenge:

Prove that there is significant difference in brain activity between having open eyes and closed eyes.

Background:

The electroencephalogram (EEG) is a representation of the electrical activity in the cerebral cortex. The cerebral cortex is the outer layer of gray matter that envelops the cerebral hemispheres. It is largely responsible for the higher brain functions, such as thought, reasoning, memory, sensation, and voluntary muscle movement. As a result, thinking or moving one’s eyes can alter the EEG readings. In this experiment, you will be studying brainwaves while the eyes are open and closed.