Visually based amendments of aiming movements: a reappraisal of Christina (1970).

The present paper examines the processing of visual information during the initial and corrective phases of an aimed movement. Visual processing in the corrective phase is related to the nature of the error in the initial phase. By producing a deliberate error, the system knows the approximate amplitude and direction in advance, allowing for the preprogramming of the corrective response. The final response, however, awaits visual confirmation with a processing time on the order of 130 msec. This strategy is feasible only if the variability in the initial response is constrained, which is the role of an additional very rapid feedback loop (70 to 100 msec.).