Roland Tay, M.D., M.A.
30 July 2012
Analyzing an Electroencephalography Report (EEG)…
The importance of complete and well recorded data in analyzing an EEG The summary of findings is only as detailed as the data reported.
The electroencephalogram, also known as the EEG is the recording of electrical activity of the brain in various states of rest or stimulation. The test is performed using the electroencephalography machine which records the brainwaves in Hz or cycles per second. The characteristics of normal brainwave have been established. Their frequency is typically between 1 and 30 hertz, having a dominant rhythm of 10 HZ and average amplitude (the height of the wave) of 20 to 100 micro volts. Not surprising, the different areas of the brain demonstrate varied frequencies. For example, the waves of the occipital lobe (processes visual stimuli) have a lower frequency than the frontal and parietal lobes (process cognitive function, speech and language and soma sensory processes, respectfully). There are four waves which are typically studied in humans. The Alpha waves which have a frequency range of 8 to 13 HZ and are seen when the subject is in a relaxed state with eyes closed. The Beta waves range 14 to 30 HZ, have lower amplitude and are generally seen when the subject is in an attentive or alert state. The Delta wave is a very large wave (high amplitude) with a frequency of 4 HZ or less and is found when the subject is in deep sleep. Theta waves are also large with a frequency of 4 to 7 Hz; normal in children, but abnormal in adults. In the ADI activity the Alpha waves were the focus for analysis. The EEG was performed using the ADI system to look at the effect of various interfering signals, examine the effect on alpha waves caused by opening and shutting the eyes, how alpha waves are affected by performing simple math equations as well as the effects on the brainwaves while listening to rock music. The exercise is used to show the students what is already published about what is known about the brain waves of humans. Materials and Methods
A computer system with ADInstruments Lab tutor software, PowerLab, Shielded Bio Amp Cable & snap-connect Shielded Lead Wires, EEG Flat electrodes, Electrode cream or past, Alcohol swabs, ink pen, abrasive pads and gel, adhesive tape and self-adhesive elastic bandage. packet titled “Electroencephalography (EEG)”, SPB11c, 9 February 2009 and LabTutor: EEG Report dated 20 July 2012, citing the volunteer as “Ashley”. Given what is known about Alpha waves the anticipation is to see the Alpha waves change with the changes in stimuli. A consideration in analysis is to first know the waves of the artifacts present at the time of the study. Artifacts are the unwanted signals caused by the volunteer moving in ways that are not requested by the study as well as external causes such as electrical fields of equipment or power supplies in the immediate area of the room. Four exercises were performed on the student volunteer, Ashley. Exercise 1:, Recognizing Artifacts, Exercise 2: Alpha & Beta Rhythm, Exercise 3: Effects of Mental Activity and Exercise 4: Effect of Auditory Stimulation. According to the data provided, the volunteer was asked to lie on her back, two electrodes were placed on the forehead, just below the hairline and a third electrode was to be placed on the back of the head in the area of the occipital lobe. The cables attached to the electrodes are terminated at the ADI machine. Preset software is utilized in these exercises, I suspect to lessen the need for the students to know the detailed technical aspects of the machinery and the software used to perform the study. In Exercise 1, the volunteer was asked to blink her eyes in rapid succession, move the eyes up, down and sideways and move her head in a repeated fashion during which the facilitator is to use the computer to annotate the start and stop of such...