Corrective loops involved in fast aiming movements: effect of task and environment.

In daily living, we continuously interact with our environment. This environment is rarely stable and living beings show remarkable adaptive capacities. When we reach for an object, it is necessary to localize the position of this object with respect to our own body before programming an adequate arm movement. If the target remains stable, the programmed movement brings the hand near the target. However, what happens when the target suddenly jumps to another position in space? The aim of this work was to investigate how rapid aiming movements are corrected when the target is displaced close to movement onset. Our results reveal that rapid movements can be modified and that the efficiency of trajectory amendments vary according to task (directional or direction/amplitude pointings) and environment (structured or darkness). We were most interested in the specific role played by peripheral and/or central feedback information (efferent copy) in the control of aiming movements. The results suggest that the two types of loops are complementary in movement regulation. However, their predominance varies according to the nature of the task at hand.