EYE-MOVEMENTS ELICITED BY TRANSPARENT STIMULI

A transparent motion condition occurs when two different motion vector s appear at the same region of an image. Such transparency during self -motion has shown demonstrable effects on perception and on the underl ying neurophysiology in the cortical and subcortical structures of pri mates. Presumably such stimulus conditions also influence oculomotor b ehavior. We investigated smooth-pursuit performance. using a transpare nt stimulus consisting of two oppositely-moving patterns. We found sli ght reduction in the mean eye velocity tracking a transparent pattern. compared with that when tracking a unidirectional pattern. Additional ly, we investigated the behavior of the optokinetic system to transpar ency. demonstrating that it elicits antagonistic optokinetic nystagmus . with distinctly reduced gain of the slow phases. Furthermore. we obs erved. during optokinetic stabilization of transparent stimuli, direct ional dominances demonstrating that subjects preferably followed one d irection. Presenting a transparent stimulus with oppositely moving pat terns and different velocities we found a general velocity dominance d emonstrating that patterns with a certain velocity are preferred. Perf orming ah experiments under dichoptic conditions produced results comp arable with those found under transparent stimulus conditions.