title: Human perceptual overestimation of whole body roll tilt in hypergravity.
abstract: Hypergravity provides a unique environment to study human perception of orientation. We utilized a long-radius centrifuge to study perception of both static and dynamic whole body roll tilt in hypergravity, across a range of angles, frequencies, and net gravito-inertial levels (referred to as G levels). While studies of static tilt perception in hypergravity have been published, this is the first to measure dynamic tilt perception (i.e., with time-varying canal stimulation) in hypergravity using a continuous matching task. In complete darkness, subjects reported their orientation perception using a haptic task, whereby they attempted to align a hand-held bar with their perceived horizontal. Static roll tilt was overestimated in hypergravity, with more overestimation at larger angles and higher G levels, across the conditions tested (overestimated by ∼35% per additional G level, P < 0.001). As our primary contribution, we show that dynamic roll tilt was also consistently overestimated in hypergravity (P < 0.001) at all angles and frequencies tested, again with more overestimation at higher G levels. The overestimation was similar to that for static tilts at low angular velocities but decreased at higher angular velocities (P = 0.006), consistent with semicircular canal sensory integration. To match our findings, we propose a modification to a previous Observer-type canal-otolith interaction model. Specifically, our data were better modeled by including the hypothesis that the central nervous system treats otolith stimulation in the utricular plane differently than stimulation out of the utricular plane. This modified model was able to simulate quantitatively both the static and the dynamic roll tilt overestimation in hypergravity measured experimentally.
authors.affiliation: Man Vehicle Laboratory, Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, Massachusetts; Charles Stark Draper Laboratory, Incorporated, Cambridge, Massachusetts; tkc@mit.edu.
authors.forename: Torin K
authors.initials: TK
authors.lastname: Clark
authors.affiliation: National Aerospace Training and Research Center, Southampton, Pennsylvania; and.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Newman
authors.affiliation: Man Vehicle Laboratory, Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, Massachusetts;
authors.forename: Charles M
authors.initials: CM
authors.lastname: Oman
authors.affiliation: Jenks Vestibular Physiology Laboratory, Massachusetts Eye and Ear Infirmary, Department of Otology and Laryngology, Harvard Medical School, Boston, Massachusetts.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Merfeld
authors.affiliation: Man Vehicle Laboratory, Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, Massachusetts;
authors.forename: Laurence R
authors.initials: LR
authors.lastname: Young
mesh_terms: D000328:Adult; D005260:Female; D018466:Gravity Sensing / Q000502:physiology*; D006801:Humans; D018471:Hypergravity; D008297:Male; D009039:Motion Perception / Q000502:physiology*; D009949:Orientation / Q000502:physiology; D012665:Semicircular Canals / Q000502:physiology*; D013028:Space Perception / Q000502:physiology*; D055815:Young Adult
keywords: human; hypergravity; orientation perception; roll tilt; vestibular