Monocular delay during visually guided actions is as effective as monocular deprivation in driving ocular dominance plasticity

In normally sighted adult volunteers, applying a monocular patch for a few hours produces a short-term shift of ocular dominance in favor of the deprived eye—a phenomenon often interpreted as a form of homeostatic plasticity. We recently showed that the same effect can be elicited without eye-patching, by delaying the image in one eye (by 333 ms) over a 1 h period, during which participants engaged in a visuomotor coordination task; at the end of this period, ocular dominance shifted in favor of the delayed eye. Here we extended these findings, showing that passive exposure to the dichoptic replay of the same video with the same monocular delay did not affect ocular dominance. Moreover, we showed that the ocular dominance shift elicited by monocular delay during goal-directed actions had the same size as the effect of monocular deprivation, achieved by replacing the delayed image with a homogeneous gray screen, and that the two effects were correlated across participants. These results suggest that homeostatic plasticity is gated by a mismatch between vision in one eye and its multimodal context, and it is not necessarily linked with visual deprivation.