Global spatial errors and local feature errors drive oculomotor learning.

Systematic intra-saccadic displacements of the saccade target object induce oculomotor learning. This type of manipulation remains undetected because of saccadic suppression of displacement. The subtle intra-saccadic manipulation causes the target object to appear at a retinal position that is inconsistent with the computed displacement of visual space during the saccade, leading to the computation of a postdicted motor error and corresponding adaptive changes to the saccade amplitude and the perceived location of objects in space. Adaptive changes to the saccade amplitude or direction have also been observed following obvious intra-saccadic manipulations, but very little is known about the characteristics of this learning process or its underlying mechanisms. The current study therefore compares oculomotor learning in response to subtle and obvious changes of the stimulus display. By measuring their effect on object localization and saccade gain, we were able to show that two different kinds of sensory error can induce oculomotor learning: a global spatial error and a local feature error. While experiencing the former leads to the typical adaptation-induced shift in perceived object location, experiencing the latter does not. On top of that, we demonstrate that adaptive adjustments to the oculomotor behavior do not necessarily rely on those sensory errors. Instead, the overt oculomotor behavior minimizes a task error.