The role of ocular muscle proprioception during modifications in smooth pursuit output.

The output of the smooth pursuit (SP) system can be increased by adding a portion of the recorded eye motion onto target motion, producing a situation analogous to that occurring with weakened ocular muscles. This change is most likely the result of alterations in the signals that code eye and target motion. We have assessed the contribution of one such signal, that arising from ocular proprioception, to the modification process during monocular SP by preventing the motion of the non-viewing eye with a suction scleral lens. The large increases normally observed for SP velocity following the modification period were substantially reduced under these conditions. Similar alterations were also observed in a manual tracking task. These results demonstrate that ocular proprioceptive signals serve to stabilize the output of the SP system following perturbations, via the recoding of eye and target motion.