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Cristina de la Malla, Joan López-Moliner; Different control modes of temporal and spatial variability in reaching movements. Journal of Vision 2012;12(9):422. doi: 10.1167/12.9.422.
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Several previous studies in motor control have looked at spatial and temporal precision of arm movements under different conditions. However, none of them have focused on the benefits of giving more time to plan the movement in terms of spatial and temporal precision. With this aim we designed a task in which participants had to point towards static targets that change their saggital position trial-to-trial. Subjects could start moving once the target changed its colour (go-signal) which took place after six possible planning times of 0, 250, 500, 1000, 2000 or 5000 ms. after target onset. In a spatial condition participants were required to be precise only spatially (on a target of 0.6 cm of diameter). In a temporal condition the response time (reaction time + movement time) had to be of 800 ms. Finally, in a combined condition, they had to meet both spatial and temporal criteria. Results show that temporal precision improved with planning time in the temporal and combined condition. Spatial precision however was not affected by planning time but in addition was as good in the temporal or combined condition as in the spatial one. Finally, it took longer to start movements when there was no time to plan them (longer reaction times) and vice versa, but these differences were compensated by modulating movement times in order to meet the required time constraint of 800 ms. We suggest that temporal variability is mainly optimized by an open-loop control mode in which movements are progressively smoother and coupled with shorter reaction times as planning time increases.
Meeting abstract presented at VSS 2012
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