Where grasps are made reveals how grasps are planned: generation and recall of motor plans

Abstract

The end-state comfort effect (Rosenbaum et al. 1990, 1992, 1993, 1996) predicts that people will grasp an object for transport in a way that allows joints to be in mid-range at the end of the transport. When participants in the present study took hold of a vertical cylinder to move it to a new position, grasp heights on the cylinder were inversely related to the height of the target position, as predicted by the end-state comfort effect. This demonstrates that where people grasp objects can give insight into the planning of movement. In the computational model of motor planning developed by Rosenbaum et al. (1995, 2001) it is assumed that goal postures are planned by a two-stage process of recall and generation. The distinction between recall and generation had not so far been tested. In the present study, the pattern of grasp heights in successive transports was consistent with the view that participants generated a plan the first time they moved the cylinder between two points, and that they subsequently recalled what they had done before, making small adjustments to that recalled plan. This outcome provides evidence for distinct effects of recall and generation on movement planning.

Preliminary Evidence for Inflexibility of Motor Planning in Children with Autism Spectrum Disorder

“…This finding indicated that participants' choice of grasp was influenced by their previous history of grasping (called hysteresis) and also implies that, up until some point of maximal discomfort, it was more costly to change the motor plan for grasping than to endure the discomfort of a grasp that was less comfortable. In other words, repeating an action is cognitively simpler than creating an entirely new motor plan [12]. Although no work has been done specifically examining hysteresis in individuals with ASD, adults with ASD exhibited greater resistance to re-planning an action they had previously performed when they had prepared to perform an alternate action, indicating a cost to formulating a motor plan other than the one they had in mind [13].…”

Grasping movement plans

“…Previous research has shown that people grasp objects differently, depending on what they intend to do with the objects (Marteniuk, MacKenzie, Jeannerod, Athenes, & Dugas, 1987). More recently, Cohen and Rosenbaum (2004) showed that when university students reached out Despite the great amount of research that has been done regarding the time it takes to move the hand to targets of varying distances and widths, it is unclear whether target distance and width are both represented in movement plans prior to movement initiation. We addressed this question by studying performance in an object manipulation task.…”

“…To address this question, we conducted a replication of Cohen and Rosenbaum's (2004) study and also varied the widths of the targets (see Figure 1). We predicted that if target height and target width are both taken into account before the plunger is grasped and brought from its home position to its target position, then grasp heights should depend on both target height and target width.…”

Is the Control of Applied Digital Forces During Natural Five-digit Grasping Affected by Carpal Tunnel Syndrome?

“…In addition, our patients with CTS showed few alterations of pair correlations with respect to the phase changes. The task-dependent patterns of five-digit grasping have been examined from the perspectives of kinematics and kinetics, and these are coordinated according to the different requirements of the tasks such as the end position or mass of an object [4,10,11,21,30,33]. During lifting and lowering, more emphasis regarding control of the digits' forces should be placed on acceleration and deceleration of objects.…”