Goal-directed reaching: movement strategies influence the weighting of allocentric and egocentric visual cues.

The location of an object in peripersonal space can be represented with respect to our body (i.e., egocentric frame of reference) or relative to contextual features and other objects (i.e., allocentric frame of reference). In the current study, we sought to determine whether the frame, or frames, of visual reference supporting motor output is influenced by reach trajectories structured to maximize visual feedback utilization (i.e., controlled online) or structured largely in advance of movement onset via central planning mechanisms (i.e., controlled offline). Reaches were directed to a target embedded in a pictorial illusion (the induced Roelofs effect: IRE) and advanced knowledge of visual feedback was manipulated to influence the nature of reaching control as reported by Zelaznik et al. (J Mot Behav 15:217-236, 1983). When vision could not be predicted in advance of movement onset, trajectories showed primary evidence of an offline mode of control (even when vision was provided) and endpoints demonstrated amplified sensitivity to the illusory (i.e., allocentric) features of the IRE. In contrast, reaches performed with reliable visual feedback evidenced a primarily online mode of control and showed increased visuomotor resistance to the IRE. These findings suggest that the manner a reaching response is structured differentially influences the weighting of allocentric and egocentric visual information. More specifically, when visual feedback is unavailable or unpredictable, the weighting of allocentric visual information for the advanced planning of a reach trajectory is increased.