Lab 6 - Lesson 3 Lesson 4 - Lab repot PDF

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Lesson 3 / Lesson 4 EEG I & EEG II

Computer #6 Arthur Lembong- Subject Max Davison-Kerwood- Analyst Mercedes Erpelding- Analyst Tim Spychalla- Analyst

Tuesday Lab Section 002 November 1, 2016

Hypothesis It is hypothesized that the alpha waves will vary with a subjects attention to mental tasks

performed with their eyes closed, and the alpha waves will diminish as the subject opens their eyes and are attentive to external stimuli. It is hypothesized that the beta waves will have smaller amplitude than the alpha waves. It is hypothesized that delta and theta waves increase during difficult mental activities requiring concentration, but won’t be seen in the experiments performed.

Specific Aims In EEG I we recorded an EEG from an awake, resting subject with their eyes open and closed and we identified and examined alpha, beta, delta and theta compounds of the EEG complex. In EEG II we recorded from an awake, resting subject while they were relaxed with their eyes closed, while they were performing mental arithmetic with their eyes closed, breathing quickly and deeply with their eyes closed and relaxed with their eyes open. We also examined the differences in the level of alpha rhythm activity during mental arithmetic and hyperventilation compared to the control condition of eyes closed and relaxed.

Background Brain is encased and protected by the cranium and the cerebral cortex is located right below the bones. Cerebral cortex is made up of nerve cells that are connected to each other and other parts of the brain. Electrical impulses are sent to and from the cortical neurons and an absence of electrical activity signifies death. The cerebral cortex functions as a center for abstract thought, reasoning, voluntary and involuntary control of skeletal muscle and the recognition of somatic, visceral and special sensory stimuli. The cerebral cortex contains the occipital lobe used for processing visual information, parietal lobe used for processing of somatosensory information such as pain and temperature, and many other processing centers. Sensory information starts in the periphery through lower centers of the brain and is sent to the cerebral cortex. When electrodes are placed on the scalp above the different areas of the cerebral cortex, electrical activity can be detected. The recording of these impulses is called an EEG. The electrode will usually detect the impulses underneath but one square millimeter of cortex has about 100,000 neurons, therefore, it can receive activity from thousands of neurons. It is only when the input to a region is synchronized with electrical activity occurring at the same time that you begin to distinguish simple, periodic wave forms in an EEG. There are four periodic rhythms that are recorded in an EEG; alpha, delta, beta and theta. The different ways are distinguished by the frequency. The alpha wave is prominent when an individual is awake but relaxed with their eyes closed. Alpha waves have the greatest amplitude from the occipital and parietal lobes. Beta rhythms occur in individuals who are alert and attentive to external stimuli or exert specific mental effort. Beta rhythm can also occur during REM in sleep. Delta and theta waves are low-frequency EEG patterns that increase during sleep in the normal adult. Sometimes delta and theta waves can be seen in individuals who are awake. Electrode positions in EEG’s are named according to the area below the scalp. The pair of electrodes measures the electrical potential difference between the two positions on the brain. EEG measurements change as an individual grows. An EEG will be more rapid with newborns and will become less rapid as they become an adult.

Methods In this experiment, we used the BIOPAC electrode lead set, 3 disposable electrodes, electrode gel, lycra swim cap press the electrodes against the head, student lab system and computer system. The subject was Arthur Lembong who is a 21 years old that weighs 83 kilograms and is 174 centimeters . When asked what his stress level was, he rated it at 3 out of a scale of 10. The subject also notified us that he was sick. First, we turned on the computer system and plugged in the equipment. Then the electrodes were set up like figure 1. Then the cap was placed on the subject’s head to press the electrodes to the scalp. Then the subject was told to get in the seated position and relax for five minutes while the electrodes established proper contact. Then the equipment was calibrated by having the subject remain relaxed with their eyes closed. After calibration, the subject remained seated, relaxed and with their eyes closed for 20 seconds. Then for another 20 seconds the director hits F4 when the subject opens their eyes and another for another 20 seconds the director hits F5 when the subject closes their eyes. Then the data was analyzed. Channel 1 was the EEG, channel 40 was the alpha wave, channel 41 was the beta wave, channel 42 was the delta wave and channel 43 was the theta wave. Then the display window was set up for optimal viewing and the I-beam cursor was used to select the first eye-closed data. Then the same was done with the eyes open data. Then the same was done for the second set of eyes closed data. 34 seconds was zoomed into on the first eyes closed data and the alpha wave was analyzed. Then two other alpha waves, beta wave, delta wave and theta waves were looked at. In this experiment, we used the BIOPAC lead set, 3 disposable electrodes, an abrasive pad, electrode gel, a swim cap, student lab system and computer system. The subject was Arthur Lembong who is 21 years old, that weighs 83 kilograms and is 174 centimeters. When asked what his stress level was, he rated it at a 3 out of a scale of 10 and he also notified us that he was sick. Then figure 1 was looked at again to make sure that the electrodes were set up properly. The electrodes should be set up correctly because it is the same as EEG I. Then a cap was placed on the subject to press the electrodes to the head. Then the subject was told to get in the seated position and wait five minutes to allow the subject to become relaxed. The calibration was set up by having the subject sit with their eyes closed and relaxed. Then the subject remained seated with their eyes

closed for ten seconds. Then the director prepares a math problem for the subject. The director verbalizes the math problem and the subject solves the math problem silently with their eyes closed for 20 seconds. Then the subject is told to remain seated and start breathing deep and rapidly for 2 minutes. Then the data was recorded for the EEG for 10 seconds. Then the subject calmed down and remained seated. The subject was allowed to open their eyes but told to avoid blinking. Data for this was recorded for 10 seconds. Then data was analyzed. Channel 1 was the EEG, channel 40 was the alpha waves and channel 41 was the alpha RMS wave. First, the I-beam was used to select the first data recording and repeated for each of the data recordings. Then a small section of the recording 1 data was zoomed into and one peak to the other in the alpha band was selected.

Results (attached at end)

Discussion EEG I Amplitude and frequency are two characteristics of regular, periodic waveforms which differentiate them from each other. Synchrony is when electrical activity matches up and it becomes easier to distinguish waveforms, alpha block is when the electrical activity is not synchronized and moving in unified motion, so there is counterbalancing. This means that synchrony will lead to larger amplitudes, though they both may have similar electrical pulses being fired. Alpha block or desynchronization just acts against itself, so waves appear smaller. The alpha waveforms of the subject in this experiment were more synchronized while the eyes were open. This is reflected in the acquired standard deviation value for the eyes open state. This could however, be an error as one would expect the alpha wave to become more desynchronized in an eyes open state. Our obtained beta values show greater desynchronization when the subject went from an eyes closed state to an eyes open state. This desynchronization also increased when the subject closed their eyes for a second time. The amplitude values for the beta waveform are not an accurate reflection of mental activity occurring with the eyes open because… Delta waveform was not noticeably affected by eyes open or closed, but theta has an appreciable difference between the two states. These waveforms are highly variable, and the difference in theta waveforms could have arisen from the emotional state of the subject while eyes were open and closed. The unchanged delta is consistent with the lack of concentration the subject had to devote to keeping their eyes open or closed. An alpha rhythm is usually between 8 and 13 Hz, and is associated with an awake, relaxed state individual. A beta rhythm is anywhere between 13 and 30 Hz, and are associated with individuals who are responding to external stimuli or exerting mental effort. A delta rhythm is between 1 and 5 Hz, which increases commonly during sleep or during difficult mental activities. Finally, theta rhythms are between 4 and 8 Hz, and can be seen during sleep, and also during states of emotional stress. EEG II The frequency of an alpha rhythm from the “eyes closed” condition was 11.765 Hz. This obtained frequency agrees with what we would expect, since alpha waves are defined as wavelengths in the range of 8 to 13 Hz. The general amplitude of EEG was highest with the eyes open, and this is also when the alpha wave levels were the highest. Based off what was learned from

the introduction, this makes sense because the occipital lobe plays a major role in the alpha wave, and this lobe would be more active when the eyes of a subject are open. The subject did not seem to require giving much concentration to the math problems. If more concentration was required, which might be the case for more difficult arithmetic, the data may reflect that with larger EEG recordings and alpha wave activity. Any amplitude difference between a subject tested alone, in a darkened room, and a subject tested in a lab full of students could come from increased activity in several different regions of the brain, such as the occipital for vision or the parietal for sensory information. The lowest alpha wave activity was recorded from recovering from hyperventilation.

Conclusion In this lab we learned how and why electroencephalography works and used this understanding to create an EEG of our subject under varying conditions. We were able to look at four component waveforms of the EEG (alpha, beta, delta and theta), and determine how changes in experimental conditionals affected their structure. Our hypothesis that the alpha waves will vary depending on the conditions was confirmed. Our data does not necessarily support our hypothesis on how the waves will change however. In our first experiment we obtained data that would suggest greater synchronization when the eyes were open, whereas in the second experiment desynchronization was greatest when the subject opened their eyes. A greater number of experiments with more than one subject would need to be ran in order to come to a legitimate conclusion regarding how alpha waves change under varying conditions.

References Pflanzer, Richard, J.C. Uyehara, and William McMullen. (2006) “Lesson 3: Electroencephalography (EEG) I Introduction.” Biopac Student Lab Manual. BIOPAC Systems, Inc., Santa Barbara, CA. p. 1-2. Pflanzer, Richard, J.C. Uyehara, and William McMullen. (2006) “Lesson 4: Electroencephalography (EEG) II Introduction.” Biopac Student Lab Manual. BIOPAC Systems, Inc., Santa Barbara, CA. p. 1-2....