Presentation Title

Lack of Preshaping Differentiates Catching from Grasping and Stopping: Support for the Dual Visuomotor Channel Theory of Prehension

Format of Presentation

Poster to be presented the Friday of the conference

Presenter Information

Youssef G. EkladuceFollow

Abstract

Reaching with a single hand to grasp an object requires the coordination of visual information related to the object, the environment, and the hand, with tactile and proprioceptive feedback from the body, in order to produce a fluid motor action. The Dual Visuomotor Channel theory proposes that the central nervous system accomplishes this by coordinating two distinct but temporally integrated movements that are mediated by different visuomotor pathways that project from visual to motor cortex via the parietal lobe. A reach movement transports the hand in relation to the object’s position and orientation, whereas the grasp preshapes the fingers in relation to the object’s size and shape. The purpose of this study is to extend the analysis of the relationship between the reach and the grasp to other moving object tasks by examining how the two movements vary when participants catch a thrown object. Participants will be presented with four different sized balls, in three different tasks: reaching-to-grasp a static object, reaching-to-stop a rolling ball, and reaching-to-catch a tossed ball. Ball Size (XS, S, M, L) and Task (grasp, stop, catch) will serve as within-subject factors for each dependent variable (reach velocity, reach trajectory, maximum pregrasp aperture, and terminal grasp aperture), which will be analyzed in separate RM-ANOVA. Preliminary results reveal that the hand does not preshape to target size as it intercepts the target during catching, but does so during grasping and stopping. The results of this project are discussed in relation to the Dual Visuomotor Channel theory.

Department

Psychology

Faculty Advisor

Jenni Karl

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Lack of Preshaping Differentiates Catching from Grasping and Stopping: Support for the Dual Visuomotor Channel Theory of Prehension

Reaching with a single hand to grasp an object requires the coordination of visual information related to the object, the environment, and the hand, with tactile and proprioceptive feedback from the body, in order to produce a fluid motor action. The Dual Visuomotor Channel theory proposes that the central nervous system accomplishes this by coordinating two distinct but temporally integrated movements that are mediated by different visuomotor pathways that project from visual to motor cortex via the parietal lobe. A reach movement transports the hand in relation to the object’s position and orientation, whereas the grasp preshapes the fingers in relation to the object’s size and shape. The purpose of this study is to extend the analysis of the relationship between the reach and the grasp to other moving object tasks by examining how the two movements vary when participants catch a thrown object. Participants will be presented with four different sized balls, in three different tasks: reaching-to-grasp a static object, reaching-to-stop a rolling ball, and reaching-to-catch a tossed ball. Ball Size (XS, S, M, L) and Task (grasp, stop, catch) will serve as within-subject factors for each dependent variable (reach velocity, reach trajectory, maximum pregrasp aperture, and terminal grasp aperture), which will be analyzed in separate RM-ANOVA. Preliminary results reveal that the hand does not preshape to target size as it intercepts the target during catching, but does so during grasping and stopping. The results of this project are discussed in relation to the Dual Visuomotor Channel theory.