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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 129 (1999), S. 362-368 
    ISSN: 1432-1106
    Keywords: Key words Binocular ; Monocular ; Disparity ; Vergence ; One-handed catching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The aim of this study was to examine the role of binocular and monocular information sources in specifying time-to-contact. More specifically, it was investigated whether the timing of the one-handed catch is consistent with a binocular tau-function strategy. Subjects (n=8) were required to time their grasp to catch a ball approaching with a constant spatial trajectory. The ball approached at three different constant velocities (1.5, 2.0 and 2.5 m/s). Vergence and disparity were manipulated through subjects wearing a telestereoscope to increase the effective interocular separation, under both binocular and monocular viewing. Subjects performed 24 trials in each of the four conditions. Subjects’ started the opening of the hand earlier in the binocular telestereoscope condition when a ball approached with velocity of 1.5 m/s. They then closed the hand earlier in the binocular telestereoscope condition at all ball approach velocities. There were no effects of telestereoscope on the timing of hand opening and closing under monocular viewing. This finding suggests the use of the binocular information in timing the grasp. However, there were effects of approach velocity under all conditions of monocular and binocular viewing. Subjects’ closed the hand earlier as a function of increasing approach velocity. Together, the effects of the telestereoscope and approach velocity indicate that timing of the one-handed catch is not consistent with the use of a binocular ”tau-function” variable. Rather, it is concluded that multiple sources of monocular and binocular information contribute to the regulation of timing.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 129 (1999), S. 369-377 
    ISSN: 1432-1106
    Keywords: Key words Adaptation ; Selection ; Re-calibration ; Timing ; One-handed catching ; Binocular information
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract   A pre-exposure, exposure, post-exposure design was used to assess the adaptation of the timing of a one-handed catch during telestereoscopic viewing. More specifically, it was examined whether the adaptation involved: (1) ignoring binocular sources of information and selecting other information, or (2) a recalibration of the coupling between the effected binocular information and the catching movement, and (3), if it is recalibration, whether it is restricted to the manipulated binocular information. To test these hypotheses, subjects (n=16) were assigned to one of two groups, each group performing three blocks of 15 trials in the dark with only the ball visible. In the exposure condition, both groups were required to catch balls under binocular telestereoscopic viewing. In the pre-exposure and post-exposure conditions, subjects performed under binocular and monocular viewing, respectively. Kinematics of the grasping movement were recorded. It was predicted that, in the case of a selection process, no afterfeffects would occur in the post-exposure condition, whereas, in the case of recalibration, aftereffects would occur. Moreover, if the recalibration is restricted to the manipulated information, only the group that was provided with binocular vision during the pre- exposure and post-exposure conditions would show aftereffects. Significant condition (pre-exposure, exposure, post-exposure) by block (first three trials, last three trials) effects were found for the moments of grasp onset, peak opening velocity and hand closure, indicating that the hand was opened and closed earlier in the first three trials of telestereoscopic viewing. This coincided with an increase in catching failures. In addition, for the moments of hand closure and peak closing velocity, negative aftereffects were found in the post-exposure condition. The hand was closed later in the first three trials after removal of telestereoscope. With respect to the presence of the aftereffects, no differences were found between the groups. It was concluded that adaptation to telestereoscopic viewing in the timing of a one-handed catch is due to the recalibration of the coupling between information and movement, rather than a selection of another source of information. Moreover, it is likely that the recalibration was not restricted to the single, manipulated information. Rather, the recalibration involves multiple binocular and monocular optical and oculomotor sources of information.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 109 (1996), S. 483-494 
    ISSN: 1432-1106
    Keywords: Movement organisation ; Movement control ; Spring perturbation ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The discrepancy between traditional (force scaling models) and the more recently conceived dynamic explanations of load compensation (λ model) was the departure point for the present study. By using the complex “open” motor skill of catching a ball rather than the traditional “closed” skills under “normal” (baseline) conditions and under conditions where a spring load was applied to the catching hand (thereby changing the dynamics of the skeleto-muscular system) it was hoped to provide further clarification of this issue. Traditional force scaling models, in this respect, would predict that maximal closing velocity of the grasp action, and movement time would not be significantly different between a control and a spring-load condition. In contrast, a dynamic system perspective would maintain that spring loading would be compensated for by a change in the rate of shift of the reciprocal command (R-command). The obtained results showed a significant difference for conditions with regard to the maximal closing velocity of the grasp action, the baseline condition being higher than the two spring-load conditions. Furthermore, a significant difference was found for the aperture at moment of catch, the aperture at moment of catch being smaller in the baseline condition than that under the two springload conditions. With regard to the temporal variables, no significant differences were obtained. A comprehensive overall explanation of the obtained data in terms of the force scaling models was not realisable. It may be that findings supporting such theories are task specific and that for constrained tasks such as catching a ball-different underlying organisational principles apply. The λ model, however, could explain adequately the obtained results. It was concluded that, except for the preparatory phase associated with load compensation before the onset of the movement of the ball, the spatiotemporal structure of the control pattern underlying catching remains the same (invariant) in both baseline and load conditions. Thereby, the spatiotemporal structure of the resulting movement changes under the influence of the load and thus is not the same for load and baseline condition.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 101 (1994), S. 314-322 
    ISSN: 1432-1106
    Keywords: One-handed catching ; Temporal constraints ; Motor control ; Kinematics ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aim of the experiment was to identify the control mechanisms involved in a goal-directed task by manipulating the temporal constraints. Subjects were required to catch, with one hand, table tennis balls projected by a ball-projection machine under five temporal conditions (ball speed ranged from 5.7 to 9 m/s, giving rise to flight times of 550-350 ms). By means of three-dimensional kinematics analysis the following results were obtained, which are some spatio-temporal adaptations of the catching movement to the increase of temporal constraints: (1) a decrease in movement time, (2) an increase in the straightness of the trajectory of the wrist, and (3) a shift backwards of the place of ball-hand contact while (4) the grasping time was kept constant. Moreover, as a result of increasing temporal constraints, the acceleration phase of the transportation component was kept constant while the deceleration phase was progressively decreased and nearly suppressed. Further, an increased correlation of the initial direction of the transportation component with the initial direction of the ball path was found. These findings show some spatio-temporal adaptations of the catching movement when the time available is manipulated. They also support the contention of a shift in the control mechanisms involved in one-handed catching facing different temporal constraints.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of child psychology and psychiatry 32 (1991), S. 0 
    ISSN: 1469-7610
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Psychology
    Notes: Abstract From birth onwards, auditory stimulation directs and intensifies visual orientation behaviour. In deaf children, by definition, auditory perception cannot take place and cannot, therefore, make a contribution to visual orientation to objects approaching from outside the initial field of view. In experiment 1, a difference in catching ability is demonstrated between deaf and hearing children (10–13 years of age) when the ball approached from the periphery or from outside the field of view. No differences in catching ability between the two groups occurred when the ball approached from within the field of view. A second experiment was conducted in order to determine if differences in catching ability between deaf and hearing children could be attributed to execution of slow orientating movements and/or slow reaction time as a result of the auditory loss. The deaf children showed slower reaction times. No differences were found in movement times between deaf and hearing children. Overall, the findings suggest that a lack of auditory stimulation during development can lead to deficiencies in the coordination of actions such as catching which are both spatially and temporally constrained.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1106
    Keywords: Time-to-contact ; Catching ; Muscle activity ; Coordination ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This study addresses the question as to the nature of the information on which the preactivation of the appropriate muscles in the grasping of the ball in a onehanded catching task is initiated and coordinated. High speed film and electromyograms were recorded while experiences subjects (N = 4) caught balls — projected towards them by a ball-machine at different speeds (11.9, 13.9 and 16.2 m/s — resulting in significantly different flight times of 508, 443 and 355 ms, respectively). Tau-margins (times to contact) values were calculated at the time of the initiation of the grasp movement for each subject at each speed. No significant differences were found between taumargins at different speeds. Further, the onset of the muscle activity for the initiation of the grasp movement was shown to be independent of ball speed. These findings lend support to the contention that the initiation of the grasp movement in catching is controlled and coordinated by the optical variable tau which specifies (directly) this time-to-contact. Given that the muscle group selected includes both flexors and extensors, co-activation on the basis of tau information is evidenced.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 93 (1993), S. 148-156 
    ISSN: 1432-1106
    Keywords: Time to contact ; Tau ; Catching ; Viewing time ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In order to explore the nature and amount of information in the optic array used by subjects required to carry out one-handed catching actions, the optical expansion pattern (using a deflating ball) and the duration of viewing time (using liquid crystal spectacles) of the ball were varied. Subjects were required to catch luminous balls (two of constant physical size and one of changing physical size during approach) attached to a pendulum in a totally dark room, while the liquid spectacles were closed at 0, 100, 200 or 300 ms before hand-ball contact. The results confirmed previous findings that the timing of the catching action is based on retinal expansion information and that conclusion was strengthened when an additional dependent variable (time of the maximal opening velocity of the grasp) was used. Further, for the viewing time duration manipulations, the time of the maximal closing velocity of the hand was later, while no effect was found on the time of the maximal opening velocity, when the last 300 ms of the trajectory of the ball was occluded. Adjustments to the catching action in response to the different ball sizes under the 0 ms condition differed significantly from the adjustments under the 300 ms condition. Both findings point to the importance of relative optical expansion information, available between 300 and 200 ms before ball-hand contact, in maintaining a (relatively) continuous perception-action coupling in the act of catching.
    Type of Medium: Electronic Resource
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