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Hal S. Greenwald, David C. Knill, Jeffrey A. Saunders; Monocular and binocular cues contribute differently to planning and online control of reaching movements. Journal of Vision 2004;4(8):143. doi: https://doi.org/10.1167/4.8.143.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose. We measured the relative contributions of monocular and binocular depth cues to planning and online control of a reaching task. Method. Subjects placed a cylinder onto a circular target surface that varied randomly in slant (orientation in depth) between trials while viewing a binocular image of the surface in a 3D virtual environment. ±5 conflicts between monocular (e.g. texture) and binocular cues were either (1) present in the stimulus at initial presentation (unperturbed trials), affecting both planning and online control, or (2) added after movement initiation (perturbation trials), affecting only the online control component of the movement. A robot arm aligned a real target surface with the virtual surface image to provide haptic feedback at the end of each trial. An optical tracking device measured the position and orientation of the cylinder throughout the movement, and the moving, oriented cylinder was also rendered in the virtual environment. On all trials, the screen flashed repeatedly for 167 ms upon movement initiation to mask the motion signal created by cue changes added in the perturbation trials. Results. In the perturbation trials, binocular cues influenced final cylinder orientation more than did monocular cues. For unperturbed trials, binocular cues remained more influential but to a lesser degree. A temporal analysis of cue weights revealed that the influence of binocular information on subjects' movements accrued faster than that of monocular information. This was consistent with the finding that final cylinder orientation was more strongly correlated with the binocular cue for fast than for slow movements. Conclusions. Humans appear to give more weight to binocular cues for online control than for planning. This can be explained by our finding that binocular cues are processed more quickly than monocular cues, effectively giving them more influence over the course of what are relatively short movements.
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