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Biological Signals Acquisition |
EOG tests > smooth pursuit |
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Humans and other primates
can follow a moving visual target of interest by generating voluntary
smooth pursuit eye movements. The smooth eye movements which are
generated are designed to keep a small moving
target on the center of the receptive surface of the eye so that it is
viewed with the greatest accuracy.
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In the absence of a moving visual target, it is not possible to generate
smooth pursuit eye movements. Therefore, it is impossible to generate
smooth pursuit eye movements with the eyes closed, in the dark, or when
viewing a stationary visual scene. |
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Procedure
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| The sweep duration is set to 10 seconds, and
the subject is told to sit 12 inches from the computer monitor. The "horizontal
pursuit" option is chosen, and the subject fixates on the moving target once it
appears. It is very important that the subject does not move his/her head. After saving
the data, the "vertical pursuit" option is chosen and the experiment is
repeated. |
Sample Target for Vertical Pursuit |
Sample Target for Horizontal
Pursuit |
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Results:
Horizontal Pursuit |
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Comments: The waveform has a triangular form. The peaks
and troughs correspond to the maximal displacements of the ball in either direction.
Calculate the amplitude in degrees of the peak to peak eye position attained during the
horizontal pursuit. Calculate the frequency of the pursuit target stimulus. |
| What are the answers for these two calculations? |
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Results:
Vertical Pursuit |
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Comments: Basically, a straight line is obtained when the
subject's eyes follow the vertically moving ball.
Why should this be? Remember that the
electrode placement in this experiment was such that only horizontal eye movements can be
recorded. |
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To
continue with the next topic, Pursuit without target, click here |