Visuomotor memory for target location in near and far reaching spaces

The authors investigated systematic error associated with endpoints of memory-guided actions performed in near and far reaching spaces. To accomplish that objective, the authors instructed 12 participants to initiate open-loop and memory-guided reaches (0, 2,000, and 5,000 ms of visual delay) from a common start position to remembered midline targets in near (i.e., a backward reach) and far (i.e., a forward reach) reaching spaces. The results indicated that near and far reaches, respectively, over- and undershot veridical target location, and the direction-specific nature of the error was amplified in the memory-guided conditions. The latter finding represents an important aspect of the present research because it suggests that the direction-specific error identified here is related to factors arising within the sensory component of the task rather than mechanical differences in reaching direction. The authors propose that stored target information serving memory guided actions is susceptible to a compression of visual space in memory such that the egocentric distance of a remembered target is underestimated.