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Craig Chapman, Dustin Kirshen, Melvyn Goodale; Seeing all the obstacles in your way: The effect of visual feedback on obstacle avoidance. Journal of Vision 2008;8(6):612. doi: https://doi.org/10.1167/8.6.612.
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© ARVO (1962-2015); The Authors (2016-present)
Human reaching behaviour displays sophisticated obstacle avoidance. Previous patient work has identified dorsal stream visuomotor processing as being integral to this ability (Schindler et al., 2004, Nature Neuroscience; Rice et al., 2006, Experimental Brain Research). Recently, we demonstrated that the obstacle avoidance system in normal participants is sensitive to both the position and size of obstacles (Chapman & Goodale, VSS 2007). A limitation in these previous studies was that reaches were performed without visual feedback, and were not made to a specific target (i.e. the target was a strip instead of a point). Many studies have shown that both the introduction of visual feedback and the order in which the feedback is received significantly alter performance in simple visuomotor tasks (e.g. Jakobson & Goodale, 1991, Experimental Brain Research). Thus, the present study was designed to compare obstacle avoidance when reaches were made to a discrete target with and without visual feedback (VF vs. NVF) under different orders of feedback availability. Twenty-four right-handed participants performed reaches in the presence of one, two, or no obstacles placed mid-reach. Three visual-feedback-order conditions were used: blocked (all VF trials occurred together, separate from NVF trials), alternating, and random. In addition to replicating the previous work, we showed that robust avoidance behaviour occurred when reaches were made to a specific target, and that visual feedback modulated this behaviour. Moreover, the order in which visual feedback was made available also had a significant impact; VF and NVF trials differed significantly across several kinematic measures but only in the blocked condition. Performance did not differ between VF and NVF trials in the alternating or random conditions, suggesting that motor strategies are automatically adjusted by recent experience (Song & Nakayama, 2007, Journal of Vision) and are not affected by explicit knowledge about feedback availability on an upcoming trial.
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