Abstract
We have recently shown that motor errors following the execution of a saccade recalibrate not only saccade but also visual space. In addition, we found that in the absence of saccade errors, visual localization became biased toward the fovea. It is an open question whether the simultaneous recalibration of motor and visual space arises because both rely on a shared resource or because both are separate but interacting. To dissociate between both models, we used saccade adaptation. We adapted saccades in outward direction by displacing the saccade target during saccade execution. We also tested visual localization in interspersed trials. After saccade adaptation trials, we applied "no error" trials in which we annulled each post-saccadic error. To this end, we predicted the saccade landing position online and presented the saccade target at the predicted position. If saccade and motor space rely on a shared resource, visual localization and saccades should show the same distortion after application of the "no error" trials. However, if both are separate, we expected that saccades remain adapted because the absence of error information would confirm the adapted amplitude. However, because visual processing does not receive information about errors, visual localization should become biased toward the fovea. We found evidence for the latter hypothesis. First, we replicated the finding of visual mislocalization following saccade outward adaptation. Second, in sessions in which "no error" trials followed adaptation trials saccade adaptation remained strong but localization became biased toward the fovea. Our data support a model of active recalibration in which saccade errors shape visual localization while processing for visual and motor space is separate.