title: Visual perception and interception of falling objects: a review of evidence for an internal model of gravity.
abstract: Prevailing views on how we time the interception of a moving object assume that the visual inputs are informationally sufficient to estimate the time-to-contact from the object's kinematics. However, there are limitations in the visual system that raise questions about the general validity of these theories. Most notably, vision is poorly sensitive to arbitrary accelerations. How then does the brain deal with the motion of objects accelerated by Earth's gravity? Here we review evidence in favor of the view that the brain makes the best estimate about target motion based on visually measured kinematics and an a priori guess about the causes of motion. According to this theory, a predictive model is used to extrapolate time-to-contact from the expected kinetics in the Earth's gravitational field.
authors.affiliation: Department of Neuromotor Physiology, IRCCS Santa Lucia Foundation, Via Ardeatina 306, 00179 Rome, Italy.
authors.forename: Myrka
authors.initials: M
authors.lastname: Zago
authors.forename: Francesco
authors.initials: F
authors.lastname: Lacquaniti
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D001132:Arm / Q000502:physiology*; D001921:Brain / Q000502:physiology*; D002986:Clinical Trials as Topic; D019317:Evidence-Based Medicine; D006112:Gravitation; D006801:Humans; D008959:Models, Neurological; D009039:Motion Perception / Q000502:physiology*; D009048:Motor Skills / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D011434:Proprioception / Q000502:physiology*; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology