PubMed · 13645242
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S GORDON. 1959. The hand in scleroderma.. https://doi.org/10.1097/00006534-195903000-00003
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In recent years, several phenomenological dynamical models have been formulated that describe how perceptual variables are incorporated in the control of motor variables. We call these short-route models as they do not address how perception-action patterns might be constrained by the dynamical properties of the sensory, neural and musculoskeletal subsystems of the human action system. As an alternative, we advocate a long-route modelling approach in which the dynamics of these subsystems are explicitly addressed and integrated to reproduce interceptive actions. The approach is exemplified through a discussion of a recently developed model for interceptive actions consisting of a neural network architecture for the online generation of motor outflow commands, based on time-to-contact information and information about the relative positions and velocities of hand and ball. This network is shown to be consistent with both behavioural and neurophysiological data. Finally, some problems are discussed with regard to the question of how the motor outflow commands (i.e. the intended movement) might be modulated in view of the musculoskeletal dynamics.
The on-line visual control of human movements can be exceptionally fast. Whether it is fast depends on the kind of visual information that is involved. In the present study we examine whether fast on-line control is specific to the magnocellular visual pathway. Fast manual responses become evident when an ongoing movement has to be adjusted, for instance because the target is displaced. We examined whether the response to such perturbations is faster for stimuli that only activate the magnocellular pathway than for equally conspicuous stimuli that only activate the parvocellular pathway. The response was indeed about 35 ms faster for stimuli that activate the magnocellular pathway. However, we argue that the slower response to stimuli that only stimulate the parvocellular pathway is due to the properties of the neurones involved and the less direct connection to the motor areas, rather than to fast reactions being driven exclusively by magnocellular input.
Tracking of a moving target usually involves coordinated movements of the eye and the hand. To study the extent to which one behavior influences the other, eye and hand movements were recorded during three conditions (eye alone, hand alone, and eye and hand together) where subjects tracked a target that initially moved in a straight line and then made an abrupt and unpredictable change in direction. The response latencies of the eye and hand were influenced by the presence of the other tracking modality. More specifically, the latency for the hand was decreased during concomitant ocular tracking, whereas the latency for the eye was increased during combined hand-eye tracking. Moreover, the velocity profile of the smooth pursuit component of ocular tracking was different when the hand also tracked the target. Taken together, these observations support the hypothesis that at least part of the neural substrate underlying tracking is shared by the two modalities.