Asymmetry in visual motion processing

THE smooth pursuit system is traditionally employed using a single small ta rget moving on a homogeneous background. It still is not fully understood, however, how accurate tracking is sustained in the presence of a structured background, which will activate global motion processing in the opposite d irection as a consequence of the ongoing eye movement. To further study thi s interaction, we used brief shifts of a textured background injected at va rious times during the initiation of smooth pursuit. While shifts opposite to the target direction did not alter smooth pursuit performance, those in the same direction resulted in a marked transient perturbation of the pursu it. These results suggest a simple yet limited mechanism that adjusts the s ensitivity of global motion processing. NeuroReport 10:2477-2480 (C) 1999 L ippincott Williams & Wilkins.