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Guoxiao Sun, Liwei Zhang, Samuel J. Vine, and Mark R. Wilson

Longer quiet eye (QE) periods are associated with better performance across a range of targeting and interceptive tasks. However, the direction of this relationship is still unclear. The two studies presented aimed to narrow this knowledge gap by experimentally manipulating QE duration—by delaying its onset or by truncating its offset—in an aiming interceptive task. In Experiment 1, the early trajectory was occluded, causing significantly shorter QE durations and worse subsequent performance. In Experiment 2, both early and/or late trajectory were occluded. Performance was degraded by the occlusion of either early or late information, and the worst performance occurred when both the early and late trajectory were occluded. Taken together, the results suggest that QE is not a by-product of performance but instead plays a causal role in supporting the interception of a moving target through a combination of preprogramming and online control processes.

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Matthew Heath

This investigation tested the proposal that a “highly accurate” and temporally unstable stored target representation is available to the motor system for the online control of memory-guided reaches. Participants reached to a target that was: (a) visible during the response, (b) extinguished at movement onset, and (c) occluded for 0, 500, 1500 and 2,500 ms in advance of response cueing. Additionally, trials were performed with (i.e., limb visible) and without (i.e., limb occluded) vision of the reaching limb. Results showed that limb occluded trials undershot the target location in each target condition, and were characterized by a primarily offline mode of control. In contrast, limb visible trials showed a consistent level of endpoint accuracy for each target condition and elicited more online reaching corrections than limb occluded trials. It is therefore proposed that a reasonably accurate and temporally stable stored target representation can be combined with vision of the moving limb for the online control of memory-guided reaches.

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Matthew Heath and David A. Westwood

We investigated whether a representation of a visual target can be stored in memory and used to support the online control of reaching movements. To distinguish between the use of a stored target representation for movement planning versus online control, we employed a novel movement environment in which participants could not fully plan their action in advance of movement initiation; that is, the spatial mapping between the movement of a computer mouse and the on-screen movement of a cursor was randomly varied from trial to trial. As such, participants were required to use online control to reach the target position. Reaches were examined in full-vision and three memory-dependent conditions (0, 2, and 5 s of delay). Absolute constant error did not accumulate between full-vision and brief delay trials (i.e., the 0-s delay), suggesting a stored representation of the visual target can be used for online control of reaching given a sufficiently brief delay interval. Longer delay trials (2 and 5 s) were less accurate and more variable than brief delay trials; however, the residual accuracy of these memory-dependent actions suggests that the motor system may have access to a stored representation of the visual target for online control processes for upwards of 5 s following target occlusion.

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Lawrence E. M. Grierson, Claudia Gonzalez, and Digby Elliott

This study was designed to examine the importance of vision to corrective processes associated with a mechanical perturbation to the limb during goal-directed aiming. With a hand held stylus, under vision and no vision conditions, performers reached to a target represented by the intersection of perpendicular lines. The stylus was connected to an air compressor and engineered such that 80 ms following movement initiation reaches were perturbed by a short air burst either in the direction of, or opposite to, the movement. Spatial position analysis of the limb at early kinematic landmarks revealed that the single direction bursts were successful in advancing and hindering the movement progress. Furthermore, within subject trial-to-trial variability analysis indicated that performers adopted different control strategies for dealing with the perturbations depending on the availability of vision. The present findings suggest that a continuous form of online control is exercised during the early portions of the aiming trajectories. This form of control may be mediated by visual or proprioceptive information.

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Jennifer Campbell, Stephanie Rossit, and Matthew Heath

, Frank, & Quinn, 1979 ), and would therefore not gauge a possible loVF advantage for online control. As such, the IDs employed by Binsted and Heath entailed movement environments that spanned reaches controlled primarily by central planning mechanisms (i.e., ID = 1.5 bits) and those requiring online

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Leonie Oostwoud Wijdenes, Eli Brenner, and Jeroen B.J. Smeets

This study set out to determine whether the fastest online hand movement corrections are only responses to changing judgments of the targets’ position or whether they are also influenced by the apparent target motion. Introducing a gap between when a target disappears and when it reappears at a new position in a double-step paradigm disrupts the apparent motion, so we examined the influence of such a gap on the intensity of the response. We found that responses to target perturbations with disrupted apparent motion were less vigorous. The response latency was 10 ms shorter when there was a gap, which might be related to the gap effect that has previously been described for initiating eye and hand movements.

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Etienne Guillaud, Martin Simoneau, Gabriel Gauthier, and Jean Blouin

The control of goal-directed arm movements performed during whole-body displacements is far from being understood. Recent studies suggested that the compensatory arm movements that allow individuals to preserve hand-in-space trajectory during unexpected body motion are controlled by sensorimotor, automatic-like processes. We tested this hypothesis comparing both the accuracy of movements directed towards body-fixed or Earth-fixed target during body rotations and the amount of interference of the reaching tasks on a concurrent cognitive task. Participants reached for a memorized 55 cm distant straight-ahead target in darkness which was about 20 cm lower than the initial finger position. The target was either body-fixed or Earth-fixed. At reaching onset, participants could be rotated in yaw. The concurrent task consisted of a verbal reaction time (RT) to an auditory stimulus. RTs increased when participants reached for the target while they were rotated. However, this increase was not significantly different for body-fixed and Earth-fixed targets. Reaching accuracy was greater for body-fixed than for Earth-fixed targets. A control experiment suggested that the errors in the Earth-fixed target condition arose from a difficulty in the organization of movements which necessitate both the production of active forces at the shoulder joint (to compensate for body rotation) and a concomitant decrease of muscular activation to lower the arm during reaching movements. These findings suggest that reaching for Earth-fixed or body-fixed targets during body rotation cannot be considered as being purely automatic tasks.

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Ann Lavrysen, Werner F. Helsen, Digby Elliott, and Jos J. Adam

The one-target advantage refers to a shorter movement time for one-target aiming movements, in comparison to aiming attempts followed by a second movement. Theoretical explanations of the one-target advantage vary in the extent to which they attribute this phenomenon to prior planning or to online control mechanisms. In this research, we attempted to gain insight into the control of sequential aiming movements by manipulating the availability of online feedback during this first or second movement component. When the participants' vision was occluded during the first movement (Experiment 1) or during the second movement (Experiment 2), their performance was affected, showing that vision was important for online control of the movement sequence. A one-target advantage was found when the second movement was in the same direction as me first, but not when it was reversed with respect to the home button. Both prior planning and online control processes contribute to the one-target advantage. The degree to which these processes are important for limb control depends on the specific task demands.

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M.A. Urbin

Goal-directed movement is possible because the cortical regions regulating movement have continuous access to visual information. Extensive research from the various domains of motor control (i.e., neurophysiology, neuropsychology, and psychophysics) has documented the extent to which the unremitting availability of visual information enables the sensorimotor system to facilitate online control of goal-directed limb movement. However, the control mechanism guiding appreciably more complex movements characterized by ballistic, whole-body coordination is not well understood. In the overarm throw, for example, joint rotations must be optimally timed between body segments to exploit the passive flow of kinetic energy and, in turn, maximize projectile speed while maintaining accuracy. The purpose of this review is to draw from the various research domains in motor control and speculate on the nature of the sensorimotor control mechanism facilitating overarm throwing performance.

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James W. Roberts, James Lyons, Daniel B. L. Garcia, Raquel Burgess, and Digby Elliott

The multiple process model contends that there are two forms of online control for manual aiming: impulse regulation and limb-target control. This study examined the impact of visual information processing for limb-target control. We amalgamated the Gunslinger protocol (i.e., faster movements following a reaction to an external trigger compared with the spontaneous initiation of movement) and Müller-Lyer target configurations into the same aiming protocol. The results showed the Gunslinger effect was isolated at the early portions of the movement (peak acceleration and peak velocity). Reacted aims reached a longer displacement at peak deceleration, but no differences for movement termination. The target configurations manifested terminal biases consistent with the illusion. We suggest the visual information processing demands imposed by reacted aims can be adapted by integrating early feedforward information for limb-target control.