15 The Multichanneling of Visual Cues and the Organization of A Visually Guided Response

A two-component model has been proposed for the regulative visual feedback involved in guiding and correcting the trajectory of an on-going pointing movement. A stroboscopic procedure has been used to study the respective roles of “position” cues, mainly processed by central vision, and of “movement” cues, processed by peripheral vision, in the organization of a visually-guided response. 1) Evidence has been obtained from a developmental study of visuomotor pointing in children to show that the slowing down of movement speed, which allows time for the closed feedback loop to operate, has to be incorporated in the feedforward component of pointing and that this incorporation is the result of a long-term process occurring between age 6 and 11. 2) Further evidence has been obtained for the separate and additive contribution of both “movement” and “positional” channels to the directional recalibration of pointing after prismatic displacement. Self-generated movement cues are exclusively encoded by peripheral vision whereas positional cues, related to the changing position of the actively or passively moving arm, are mainly processed by central vision. 3) A selective long-term deprivation of the “movement channel” from birth does not preclude the development of visuo-motor coordination in the kitten, as long as stroboscopic illumination at a fixed frequency is used. In contrast, the use of a random flashing light during rearing leads to a significant impairment of the visual guidance of the forelimb without impairing the visually guided locomotion of the kitten.