Having to identify a target reduces latenciesin prosaccades but not in antisaccades

摘要

In a princeps study, Trottier and Pratt (2005)showed that saccadic latencies were dramatically reducedwhen subjects were instructed to not simply look at aperipheral target (reflexive saccade) but to identify some ofits properties. According to the authors, the shortening ofsaccadic reactions times may arise from a top-down disin-hibition of the superior colliculus (SC), potentially medi-ated by the direct pathway connecting frontal/prefrontalcortex structures to the SC. Using a "cue paradigm" (a cuepreceded the appearance of the target), the present studytests if the task instruction (Identify vs. Glance) alsoreduces the latencies of antisaccades (AS), which involveprefrontal structures. We show that instruction reduceslatencies for prosaccade but not for AS. An AS requirestwo processes: the inhibition of a reflexive saccade and thegeneration of a voluntary saccade. To separate these pro-cesses and to better understand the task effect we also testthe effect of the task instruction only on voluntary saccades.The effect still exists but it is much weaker than for reflex-ive saccades. The instruction effect closely depends on taskdemands in executive resources.