Calibrating grasp size and reach distance: interactions reveal integral organization of reaching-to-grasp movements

• DOI: 10.1007/s00221-008-1418-5
• Publication Date: 2008-05-20T13:29:29Z
• Authors: Rachel Coats; Geoffrey P. Bingham; Mark Mon-Williams
• Keywords: Adult; Hand Strength; Movement; Calibration; 05 social sciences; Humans; 0501 psychology and cognitive sciences; Photic Stimulation; Psychomotor Performance

Feedback is a central feature of neural systems and of crucial importance to human behaviour as shown in goal directed actions such as reaching-to-grasp. One important source of feedback in reach-to-grasp behaviour arises from the haptic information obtained after grasping an object. We manipulated the felt distance and/or size of a visually constant object to explore the role of haptic information in the calibration of reaching and grasping. Crucially, our design explored post-adaptation effects rather than the previously documented role of haptic information in movement organisation. A post-adaptation reach-to-grasp task showed: (1) distorted haptic feedback caused recalibration; (2) reach distance and grasp size could be calibrated separately but, if calibrated simultaneously, then (3) recalibration was greater when distance and size changed in a consistent (e.g. reaching for a larger object at a greater distance) rather than an inconsistent (e.g. a smaller object at a greater distance) fashion. These interactions reveal the integral nature of reach-to-grasp organization, that is, that reaching and grasping are integrated components of a single action system.