title: Visuomotor adaptation changes stereoscopic depth perception and tactile discrimination.
abstract: Perceptual judgments of relative depth from binocular disparity are systematically distorted in humans, despite in principle having access to reliable 3D information. Interestingly, these distortions vanish at a natural grasping distance, as if perceived stereo depth is contingent on a specific reference distance for depth-disparity scaling that corresponds to the length of our arm. Here we show that the brain's representation of the arm indeed powerfully modulates depth perception, and that this internal calibration can be quickly updated. We used a classic visuomotor adaptation task in which subjects execute reaching movements with the visual feedback of their reaching finger displaced farther in depth, as if they had a longer arm. After adaptation, 3D perception changed dramatically, and became accurate at the "new" natural grasping distance, the updated disparity scaling reference distance. We further tested whether the rapid adaptive changes were restricted to the visual modality or were characteristic of sensory systems in general. Remarkably, we found an improvement in tactile discrimination consistent with a magnified internal image of the arm. This suggests that the brain integrates sensory signals with information about arm length, and quickly adapts to an artificially updated body structure. These adaptive processes are most likely a relic of the mechanisms needed to optimally correct for changes in size and shape of the body during ontogenesis.
authors.affiliation: Center for Neuroscience and Cognitive Systems@UniTn, Istituto Italiano di Tecnologia, Rovereto 38068, Italy, Department of Life Science, University of Trieste, Trieste 34128, Italy, Department of Psychology, Università degli Studi di Firenze, Firenze 50135, Italy, Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, and Department of Cognitive, Linguistic and Psychological Sciences, Brown University, Providence, Rhode Island 02912.
authors.forename: Robert
authors.initials: R
authors.lastname: Volcic
authors.forename: Carlo
authors.initials: C
authors.lastname: Fantoni
authors.forename: Corrado
authors.initials: C
authors.lastname: Caudek
authors.forename: John A
authors.initials: JA
authors.lastname: Assad
authors.forename: Fulvio
authors.initials: F
authors.lastname: Domini
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D003867:Depth Perception; D004192:Discrimination, Psychological; D025461:Feedback, Physiological; D005260:Female; D005385:Fingers / Q000294:innervation / Q000502:physiology; D006801:Humans; D008297:Male; D009068:Movement; D011597:Psychomotor Performance / Q000502:physiology*; D055698:Touch Perception