Figure 1. Experimental setup.

(A) The monkey had to execute a precision grip in order to open the door of the food container. The target door, back-illuminated by a LED, was covered by an outer sliding door (Door) that the experimenter opened at each trial onset, giving the monkey a go-signal to start moving the hand from the resting position. The dashed line (IR) represents an infrared barrier positioned in front of the apparatus. (B) Time sequence of events during the grasping task and neuron recording. During the flash conditions, the scene was briefly illuminated by a single 20 µs xenon light flash delivered when the hand crossed an infrared barrier at 10 cm in front of the apparatus (PT-flash) or when both the thumb and index finger touched two small metal contact sensors attached to the sides of the to-be-grasped handle (T-flash).