Biomedical subjects

Gordon Binsted

Publications and source records attributed to Gordon Binsted.

6 recordsLinked to original sources

PubMed2006

Visuomotor representation decay: influence on motor systems.

The contribution of ventral stream information to the variability of movement has been the focus of much attention, and has provided numerous researchers with conflicting results. These results have been obtained through the use of discrete pointing movements, and as such, do not offer any explanation regarding how ventral stream information contributes to movement variability over time. The present study examined the contribution of ventral stream information to movement variability in three tasks: Hand-only movement, eye-only movement, and an eye-hand coordinated task. Participants performed a continuous reciprocal tapping task to two point-of-light targets for 10 s. The targets were visible for the first 5 s, at which point vision of the targets was removed. Movement variability was similar in all conditions for the initial 5-s interval. The no-vision condition (final 5 s) can be summarized as follows: ventral stream information contributed to an initial significant increase in variability across motor systems, though the different motor systems were able to preserve ventral information integrity differently. The results of these studies can be attributed to the behavioral and cortical networks that underlie the saccadic and manual motor systems.

Adult↗

PubMed2006

Decay in visuomotor representations during manual aiming.

The time course of the decay of spatial representations used for planning and controlling manual aiming has not been established. The authors' purpose in the present investigation was to generate a psychometric function for memory-guided reaching movements. Eight university-aged students performed a reciprocal tapping task for 10 s. Participants could see the targets for 5 s; then, vision of the targets was occluded. The present findings provide mixed support for 2 prominent theories concerning memory representations. Variability increased concurrently with the removal of vision of the targets, supporting the real-time hypothesis. However, a brief plateau in the curve was apparent for approximately 2 s after vision was removed, consistent with the use of a highly accurate representation for action.

Hand↗

PubMed2005

Manual asymmetries in bimanual reaching: the influence of spatial compatibility and visuospatial attention.

The goal of the present investigation was to explore the possible expression of hemispheric-specific processing during the planning and execution of a bimanual reaching task. Participants (N = 9) completed 80 bimanual reaching movements (requiring simultaneous, bilateral production of arm movements) to peripherally presented targets while selectively attending to either their left or right hand. Further, targets were presented in spatially compatible (ipsilateral to the aiming limb) and incompatible (contralateral to the aiming limb) response contexts. It was found that the left hand exhibited temporal superiority over the right hand in the response planning phase of bimanual reaching, indicating a left hand/right hemisphere advantage in the preparation of a bimanual response. During response execution, and consistent with the view that interhemispheric processing time (Barthelemy & Boulinguez, 2002) or biomechanical constraints (Carey, Hargreaves, & Goodale, 1996) generate temporal delays, longer movement times were observed in response to spatially incompatible target positions. However, no hemisphere-specific benefit was demonstrated for response execution. Based on these findings, we propose lateralized processing is present at the time of response planning (i.e., left hand/right hemisphere processing advantage); however, lateralized specialization appears to be annulled during dynamic execution of a bimanual reaching task.

Adult↗

PubMed2004

Can the motor system resolve a premovement bias in grip aperture? Online analysis of grasping the Müller-Lyer illusion.

The goal of the present investigation was to determine the time-course by which the motor system might resolve the context-dependent effects of a visual illusion [i.e., the Müller-Lyer (ML) figure]. Specifically, we asked participants to scale their grip aperture (GA) to the perceived size of an object embedded within a ML figure in advance of closed-loop (CL) and open-loop (OL) grasping movements. As a result, premovement GA was biased in a direction consistent with the perceptual effects of the illusion. We reasoned that such a manipulation might provide a novel opportunity to determine whether the motor system is able to resolve a biased GA immediately following the onset of a response [i.e., in accord with the perception/action model (PAM); Milner and Goodale 1995, The visual brain in action, Oxford University Press], or gradually as the action unfolds [i.e., in accord with the planning/control model (PCM); Glover and Dixon 2002, Percept Psychophys 64:266-278]. It was found that biasing GA in advance of movement resulted in a reliable effect of the ML figure throughout CL and OL trials (i.e., up to 80% of grasping time). Although the present findings appear contrary to the theoretical tenets of the PAM and the PCM, it is proposed that biasing GA in advance of movement leads to offline visual processing and a feedforward mode of grasping control, thus accounting for the illusion-induced effect throughout the grasping response.

Adult↗

PubMed2004

The control of memory-guided reaching movements in peripersonal space.

The goal of the present investigation was to explore the putative contributions of feedforward- and feedback-based processes in the control of memory-guided reaching movements. Participants (N = 4) completed an extensive number of reaching movements (2700) to 3 midline targets (20, 30, 40 cm) in 6 visual conditions: full-vision, open-loop, and four memory-guided conditions (0, 200, 400, and 600 ms of delay). To infer limb control, we used a regression technique to examine the within-trial correspondence between the spatial position of the limb at peak acceleration, peak velocity, peak deceleration, and the ultimate movement endpoint. A high degree of within-trial correspondence would suggest that the final position of the limb was largely specified prior to movement onset and not adjusted during the action (i.e., feedforward control); conversely, a low degree of within-trial correspondence would suggest that movements were modified during the reaching trajectory (i.e., feedback control). Full-vision reaches were found to be more accurate and less variable than open-loop and memory-guided reaches. Moreover, full-vision reaches demonstrated only modest within-trial correspondence between the spatial position of the limb at each kinematic marker and the ultimate movement endpoint, suggesting that reaching accuracy was achieved by adjusting the limb trajectory throughout the course of the action. Open-loop and memory-guided movements exhibited strong within-trial correspondence between final limb position and the position of the limb at peak velocity and peak deceleration. This strong correspondence indicates that the final position of the limb was largely determined by processes that occurred before the reach was initiated; errors in the planning process were not corrected during the course of the action. Thus, and contrary to our previous findings in a video-based aiming task, it appears that stored target information is not extensively (if at all) used to modify the trajectory of reaching movements to remembered targets in peripersonal space.

Adult↗

PubMed1999

Goal-Directed Aiming: Correcting a Force-Specification Error With the Right and Left Hands.

In 2 experiments, the authors examined manual aiming asymmetries as well as the ability of participants to adjust their aiming trajectories following an unexpected change to the inertial resistance to movement. In Experiment 1, participants (N = 11) were able to rapidly adjust their movement trajectories to conform to the new movement requirements. They were faster and more consistent when aiming with their right hand than with their left hand, regardless of whether or not the movement was perturbed. In Experiment 2, participants' (N = 11) vision of the hand was manipulated so that the role of visual feedback in the corrective process could be examined. Vision had an impact not only on performance but also on the characteristics of the movement trajectories. Manual asymmetries in aiming were associated with a right hand superiority during the final corrective stages of the movement.

Journal Article↗