Adaptation to an altered relation between retinal image displacements and saccadic eye movements.

The normal relation between retinal image displacement and saccadic eye movement was experimentally altered by moving a stimulus vertically up or down contingent upon a subject’s horizontal saccades. For half the subjects the stimulus moved up with a rightward and down with a leftward saccade. while for the other subjects the reverse was the case. Prior to and following 45 min of exposure to this novel situation, detection thresholds for vertical up and down motion during rightward saccades were determined. The exposure condition produced a significant mean increase of 7.8% in the threshold for vertical motion in the same direction as the adapting stimulus had displaced with rightward saccades during exposure. and a mean decrease in the threshold for motion in the opposite direction of 6.4%. The exposure condition also produced a significant post-test change in saccadic trajectory. The results are evidence of a significant tendency toward the re-establishment of position constancy when there is an altered relation between image displacements and saccadic eye movements. Based on the change in saccadic trajectory, an argument is made that the adaptation is caused by a recalibration of registered eye movemen; dire&ion. -