Peripheral stimulation and human cyclofusional response.

Cyclofusional responses consisting of both motor and nonmotor components were measured during stimulation in the peripheral visual field. A 5.75 degree torsional disparity presented in 10 degrees, 30 degrees, and 50 degrees diameter visual stimulus fields induced binocular, torsional eye movements averaging 2.8 degrees to 3.4 degrees. When torsional disparity was excluded from regions up to 30 degrees diameter in the center of the visual field, binocular torsional eye movements of 3.5 degrees to 4.4 degrees were observed. A presentation of simultaneous, conflicting torsional disparities in center and annular surround regions of the stimulus field also induced torsional eye movements which reduced the disparity in only one of the two regions while increasing it in the other. The directions of eye movement changed when the surround stimulus area was enlarged at the expense of the area of the conflicting central stimulus. Based on an objective method of monitoring eye position, the findings in this report suggest that peripheral stimulation exercises a strong influence on the cyclofusional motor response component and that under suitable conditions such stimulation may have a greater influence on the cyclofusional motor response than central stimulation.