Submitted on August 10, 2007
Accepted on December 3, 2007
Vestibular nuclei and cerebellum put visual gravitational motion in context
William Lewis Miller1*, Vincenzo Maffei2, Gianfranco Bosco3, Marco Iosa2, Myrka Zago2, Emiliano Macaluso4, and Francesco Lacquaniti5
1 Dept. of Neuromotor Physiology, Santa Lucia Foundation, Rome, Italy; Neuroimaging Laboratory, Santa Lucia Foundation, Rome, Italy
2 Dept. of Neuromotor Physiology, Santa Lucia Foundation, Rome, Italy
3 Department of Neuroscience, University of Rome Tor Vergata, Rome, Italy; Center of Space Biomedicine, University of Rome Tor Vergata, Rome, Italy
4 Neuroimaging Laboratory, Santa Lucia Foundation, Rome, Italy
5 Dept. of Neuromotor Physiology, Santa Lucia Foundation, Rome, Italy; Department of Neuroscience, University of Rome Tor Vergata, Rome, Italy; Center of Space Biomedicine, University of Rome Tor Vergata, Rome, Italy
* To whom correspondence should be addressed. E-mail: w.miller{at}hsantalucia.it.
Animal survival in the forest, and human success on the sports field, often depend on the ability to seize a target on the fly. All bodies fall at the same rate in the gravitational field, but the corresponding retinal motion varies with apparent viewing distance. How then does the brain predict time-to-collision under gravity? A perspective context from natural or pictorial settings might afford accurate predictions of gravity's effects via the recovery of an environmental reference from the scene structure. We report that embedding motion in a pictorial scene facilitates interception of gravitational acceleration over unnatural acceleration, whereas a blank scene eliminates such bias. Functional magnetic resonance imaging (fMRI) revealed BOLD correlates of these visual context effects on gravitational motion processing in the vestibular nuclei and posterior cerebellar vermis. Our results suggest an early stage of integration of high-level visual analysis with gravity-related motion information, which may represent the substrate for perceptual constancy of ubiquitous gravitational motion.
