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In the last lab, you demonstrated that most subjects when relaxing will have alpha rhythms in their brain waves and that most subjects will have fewer alpha rhythms problem solving. This reduction in alpha production is not always symmetrical and may vary with the task (Andreassi, 2000, p. 44; Davidson, 1998).

Fig 1

On Channel 2 it may be evident that there is a beta like rhythm after the event marker on Channel 4 which marks the instruction to repeat the alphabet covertly. Note that the beta rhythm is not evident on Channel 3 which shows a lot of alpha frequency brain waves. Channel 2 is from the left hemisphere and Channel 3 is from the right. Channel 1 is a 1 second timer.

METHOD

Apparatus
Coulbourne bioamplifiers will amplify the signals to be displayed on the Windows 2000 computer.

Procedure

To complete this lab, follow the instructions for electrode attachment used in the Lab Two, except attach the two EEG electrodes at F3 & F4.

Stimuli for laterality lab: Note that after each task the participant is to say "OK, I am finished" and that is all that the participant should say. We don't want the EEG to be contaminated by speech. All movement is to be kept to a minimum.

1. Have the participant relax for 2-3 min Verbal Stimuli (please do in order).

2. Have the participant recite the alphabet covertly (to themselves-not out loud). Mark the record .

3. Have the participant repeat the pledge of allegiance to themselves and instruct them to "fake it" if the cannot remember all of the words. Mark the record.

4. Have the participant repeat the alphabet covertly Imagery instructions.

5. Have the participant attempt to recall what the instructor is wearing today (covertly-for a later test). Mark the record.

6. Have the participant imagine how the table looked at his or her last meal (covertly -for a later test). Mark the record Have the subject imagine rotating the figure supplied by 90 degrees (covertly for a later sketch) in his or her "mind's eye".

 Fig 2

Stimulus for mental rotation task.

Review recordings from the computer memory. Using the instructions from notes on the Computer Instructions complete a Fast Fourier (DFT) Analysis of segments of the left and right EEG electrodes for the verbal and nonverbal tasks.

Care for electrodes after removal from skin as explained in labs #1 & 2.

Fig 3

DFT analysis showing power by frequency with the cross hairs at the center of the alpha frequency.

LAB QUESTIONS

1. Discuss the purpose of Fast Fourier Analysis.

1. Enter your findings:

Power at 10hz	Left Hemisphere	Right Hemisphere
Verbal Task
Spatial Task

2. How does that differ from the ideal?

2. Compare the output of the FFA, the alpha filter from Lab2 and "raw" EEG.

3. How else might FFA be used?

REFERENCES

Andreassi, J. L. (2000). Psychophysiology Human Behavior & Physiological Response.Hillsdale, New Jersey: Earlbaum.

Davidson, R.J. (1998) Anterior Electrophysiological Asymmetries, emotion, and depression: Conceptual and methodological conundrms. Psychophysiology, 35, 607-614.