title: On-line visual control of grasping movements.
abstract: Even though it is recognized that vision plays an important role in grasping movements, it is not yet fully understood how the visual feedback of the hand contributes to the on-line control. Visual feedback could be used to shape the posture of the hand and fingers, to adjust the trajectory of the moving hand, or a combination of both. Here, we used a dynamic perturbation method that altered the position of the visual feedback relative to the actual position of the thumb and index finger to virtually increase or decrease the visually sensed grip aperture. Subjects grasped objects in a virtual 3D environment with haptic feedback and with visual feedback provided by small virtual spheres anchored to the their unseen fingertips. We found that the effects of the visually perturbed grip aperture arose preeminently late in the movement when the hand was in the object's proximity. The on-line visual feedback assisted both the scaling of the grip aperture to properly conform it to the object's dimension and the transport of the hand to correctly position the digits on the object's surface. However, the extent of these compensatory adjustments was contingent on the viewing geometry. The visual control of the actual grip aperture was mainly observed when the final grasp axis orientation was approximately perpendicular to the viewing direction. On the contrary, when the final grasp axis was aligned with the viewing direction, the visual control was predominantly concerned with the guidance of the digit toward the visible final contact point.
authors.affiliation: Center for Neuroscience and Cognitive Systems@UniTn, Istituto Italiano di Tecnologia, 38068, Rovereto, Italy. robert.volcic@nyu.edu.|Department of Psychology, New York University Abu Dhabi, PO Box 129188, Abu Dhabi, United Arab Emirates. robert.volcic@nyu.edu.
authors.forename: Robert
authors.identifier: 0000-0002-0170-4136
authors.initials: R
authors.lastname: Volcic
authors.affiliation: Center for Neuroscience and Cognitive Systems@UniTn, Istituto Italiano di Tecnologia, 38068, Rovereto, Italy.|Department of Cognitive, Linguistic and Psychological Sciences, Brown University, Providence, RI, 02912, USA.
authors.forename: Fulvio
authors.initials: F
authors.lastname: Domini
mesh_terms: D000328:Adult; D056228:Feedback, Sensory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D013028:Space Perception / Q000502:physiology*; D055698:Touch Perception / Q000502:physiology; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
keywords: Grasping; On-line control; Perturbation; Virtual reality; Visual feedback