title: Hand shaping using hapsis resembles visually guided hand shaping.
abstract: The reach-to-grasp movement is composed of a number of movement elements including hand transport, hand shaping, and grasping. These movement elements are featured in grasping when it is guided by vision, when it is guided by haptic input from the non-reaching hand or other body parts, and when it is guided by off-line perceptual (remembered) knowledge. An unanswered question is how is the reach-to-grasp movement achieved when all information about the target must be acquired by the grasping hand? The answer to this question was obtained by asking participants to reach for three randomly presented food items that varied in size: an orange slice, a small round donut ball, or a blueberry. In order to constrain the grasping pattern, participants were asked to pick up an item with the intention of placing it in the mouth. Thus, in the unsighted condition, participants did not know which item they were reaching for until they made haptic contact with it. Hand transport, shaping, and grasping were examined using frame-by-frame video analysis and linear kinematics. These measures showed that in unsighted reaching, hand transport first served to establish haptic contact between either the second or third digit and the target. After haptic identification of the target, the hand and/or grasping digits adjusted their trajectory, reshaped, and reoriented for grasping. A comparison of haptically guided grasping and visually guided grasping indicated that the two were very similar. This similarity is discussed in relation to contemporary ideas concerning the neural mechanisms that guide hand use.
authors.affiliation: Department of Neuroscience, Canadian Centre for Behavioural Neuroscience, University of Lethbridge, Lethbridge, AB, T1K 3M4, Canada. jenni.karl@uleth.ca
authors.forename: Jenni M
authors.initials: JM
authors.lastname: Karl
authors.forename: Lori-Ann R
authors.initials: LA
authors.lastname: Sacrey
authors.forename: Jon B
authors.initials: JB
authors.lastname: Doan
authors.forename: Ian Q
authors.initials: IQ
authors.lastname: Whishaw
mesh_terms: D000293:Adolescent; D001696:Biomechanical Phenomena; D056228:Feedback, Sensory / Q000502:physiology*; D005260:Female; D006225:Hand / Q000294:innervation / Q000502:physiology; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D008297:Male; D009068:Movement / Q000502:physiology; D011336:Probability; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D013997:Time Factors; D014110:Touch / Q000502:physiology*; D055815:Young Adult