The McGill Physiology Virtual Lab

Biological Signals Acquisition

EOG tests > smooth pursuit

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.

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.
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

Results: Horizontal Pursuit

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?


Results: Vertical Pursuit

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.

To continue with the next topic, Pursuit without target, click here