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This article describes a model of motion planning instantiated for grasping. According to the model, one of the most important aspects of motion planning is establishing a constraint hierarchy--a set of prioritized requirements defining the task to be performed. For grasping, constraints include avoiding collisions with to-be-grasped objects and minimizing(More)
Whereas previous studies on interlimb coordination have mainly underscored the ubiquitous tendency to synchronize the motions of the limbs, the present experiment revealed a small, but distinct, interlimb asynchrony or phase offset, i.e. the dominant limb led the non-dominant limb during the production of bimanual circle drawing. This asynchrony was clearly(More)
In this study we investigated the relative impact of planning and execution constraints on discrete bimanual task performance. In particular, in a bimanual CD-placement task, we compared people's preference to end movements comfortably with their preference to move symmetrically. In "Experiment 1" we examined the degree of interlimb coupling as participants(More)
This article describes a theory of the computations underlying the selection of coordinated motion patterns, especially in reaching tasks. The central idea is that when a spatial target is selected as an object to be reached, stored postures are evaluated for the contributions they can make to the task. Weights are assigned to the stored postures, and a(More)
Tasks that are easy when performed in isolation become difficult when performed simultaneously in the upper and/or lower limbs. This observation points to basic CNS constraints in the organization of patterns of interlimb coordination. The present studies provide evidence for the existence of two basic coordinative constraints whose effects may be additive(More)
Humans are experts in cooperating with each other when trying to accomplish tasks they cannot achieve alone. Recent studies of joint action have shown that when performing tasks together people strongly rely on the neurocognitive mechanisms that they also use when performing actions individually, that is, they predict the consequences of their co-actor's(More)
In this study, a paradigm is presented for the assessment of manual dexterity in subjects with cerebral palsy (CP) that divides the prehensile action into a 'time-to-contact' phase and a 'time-in-contact' phase. Two experiments were performed that determined the effect of object weight on the timing of both phases for the impaired hand and non-impaired hand(More)
Humans are frequently confronted with goal-directed tasks that can not be accomplished alone, or that benefit from co-operation with other agents. The relatively new field of social cognitive neuroscience seeks to characterize functional neuroanatomical systems either specifically or preferentially engaged during such joint-action tasks. Based on(More)
The authors performed a behavioral study of the complexity of left-hand finger movements in classical guitar playing. Six professional guitarists played movement sequences in a fixed tempo. Left-hand finger movements were recorded in 3 dimensions, and the guitar sound was recorded synchronously. Assuming that performers prefer to avoid extreme joint angles(More)
The kinematics and intrinsic dynamics of reaching and grasping movements in six subjects with spastic hemiparesis were studied. Movements were performed with both hands together as well as with each hand in isolation, and two target widths were used. As expected, large manual asymmetries existed in unimanual task performance. These asymmetries were more(More)