Abstract
Short term monocular deprivation modulates ocular dominance, such that the previously deprived eye’s contribution to the binocular percept increases, supposedly as a result of changes in contrast-gain. Therefore, as a result of an increase in contrast-gain, the processing time of the previously patched eye would be expected to speed up. The aim of this study is to test this hypothesis by examining the effects of short-term monocular deprivation on interocular synchronicity.
In order to measure the interocular delay, we used a paradigm based on the Pulfrich phenomenon where a cylinder rotating in depth, defined by moving Gabor patches, is presented at different interocular phases generating strong to ambiguous depth percepts. Hence, the point of subjective equality at which the cylinder is seen rotating ambiguously (i.e. is appearing flat) characterizes the interocular delay. The interocular delay was measured at baseline before patching and at outcome, after one hour of monocular deprivation. Eight conditions were tested, defined by the patched eye (left or right), the spatio-temporal properties of the stimulus (small and slow or large and fast) and the type of patch worn during the patching period (translucent or opaque).
Contrary to expectations, short-term monocular deprivation induces an interocular delay in the previously patched eye. The amplitude of this effect is larger following opaque patching compared to translucent patching.
Our results demonstrate a negative effect – i.e. a slowing down in the processing time of the previously patched-eye – induced by short term monocular deprivation. This suggests that the plasticity effects of monocular deprivation are not exclusively mediated by contrast-gain mechanisms and that light adaptation mechanisms might also be involved in the plasticity resulting in processing delays as a result of short-term monocular deprivation.