Action control: independent effects of memory and monocular viewing on reaching accuracy

Evidence suggests that perceptual networks in the ventral visual pathway are necessary for action control when targets are viewed with only one eye, or when the target must be stored in memory. We tested whether memory-linked (i.e., open-loop versus memory-guided actions) and monocular-linked effects (i.e., binocular versus monocular actions) on action arise from a common mechanism as suggested by evidence from neuropsychology and psychophysics. Participants viewed targets with either one eye or two (vision: monocular versus binocular) and then reached to touch targets in open-loop and memory-guided conditions (condition: open-loop versus 0, 500, 1000, and 1500 ms delays). Results showed that memory-linked and monocular-linked increases in radial and variable movement error were additive (i.e., main effects of vision and condition, but no interaction). This suggests that the two effects on visuomotor control arise from separate mechanisms, in contrast to evidence from psychophysics and neuropsychology suggesting a common underlying mechanism.