Adaptation to a novel gravitational state involves adaptation of vestibular mediated responses, in particular those mediated by the otolith organs. The present paper investigates whether the orientation of Listings plane, which is under control of otolith signals, is affected by sustained exposure to hypergravity. Subjects were exposed to four G-loads differing in duration (45 or 90 min) and magnitude (2 or 3G). During centrifugation subjects were in a supine position, directing the gravito-inertial acceleration along the naso-occipetal axis. We determined the orientation of Listings plane before and after each centrifuge run, with the head erect and tilted in pitch. Head tilt in pitch induced a counter-pitch of Listings plane, which was found to be less pronounced after centrifugation. In addition, exposure to 3G for 90 min induced a small backward tilt of Listings plane compared to the pretest orientation (head erect). In order to explain these results a hypothesis is discussed, proposing that the orientation of Listings plane in the head is governed by a head fixed orientation vector that is modulated by the direction of gravity relative to the head. Sustained centrifugation is proposed to decrease this gravitational modulation, leading to the effects observed. This could reflect a shift towards a more body centered frame of reference. Keywords: Three-dimensional eye movements, listings plane, hypergravity, vestibular adaptation, head pitch
De mens kan zich aanpassen aan nieuwe zwaartekrachtsniveaus (gewichtloosheid, maan, mars, ... en ook in een centrifuge). Uit dit onderzoek blijkt dat ook uit de manier waarop we onze ogen bewegen, wat ons weer meer inzicht geeft in de referentie-kaders die ons centraal zenwustelsel gebruikt voor het inschatten van zelfbeweging en -orientatie t.o.v. de zwaartekracht