Human ocular counterrolling during roll-tilt and centrifugation.
To test a hypothesis about how otoliths resolve roll-tilts from translations, we measured human ocular torsion position [ocular counterrolling (OCR)] to maintained linear acceleration stimuli. All subjects (n = 8) were tested in two conditions where the same magnitude of shear along an interaural axis was generated in one of two ways: either by roll-tilt on a tilt-chair in a 1-g environment, or by centripetal linear acceleration during constant velocity rotation 1 m from the axis of rotation on a fixed-chair human centrifuge. The interaural shear to the otoliths was the same for these two conditions, but the dorsoventral shear was different and for all eight subjects the OCR on the centrifuge was significantly greater than the torsion on the tilt-chair, although the resultant angle was in fact smaller on the centrifuge than on the tilt-chair. The results confirm that dorsoventral shear is important for determining OCR. The otoliths may resolve potential stimulus ambiguities between tilts and translations by virtue of the different patterns of interaural and dorsoventral shear that these stimuli generate.
MacDougall
H G
HG
Department of Psychology, University of Sydney, New South Wales, Australia.
Curthoys
I S
IS
Betts
G A
GA
Burgess
A M
AM
Halmagyi
G M
GM
D000054:Acceleration; D000328:Adult; D002498:Centrifugation; D005133:Eye Movements / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D010037:Otolithic Membrane / Q000502:physiology; D010812:Physical Stimulation; D011187:Posture / Q000502:physiology*; D013314:Stress, Mechanical