Accession Number : ADA320766

Title :   Otolith Contribution to Ocular Torsion and Spatial Orientation During Acceleration.

Descriptive Note : Final rept.,

Corporate Author : NAVAL AEROSPACE MEDICAL RESEARCH LAB PENSACOLA FL

Personal Author(s) : De Graaf, B. ; Bos, J. E. ; Tielemans, W. ; Rameckers, F. ; Rupert, A. H. ; Guedry, F. E.

PDF Url : ADA320766

Report Date : SEP 1996

Pagination or Media Count : 27

Abstract : Humans perceive linear acceleration and tilt by the otoliths as a result of shear forces on the maculae. A paradigm was set up to study the influence of forces from different directions on the otoliths, on eye movements and tilt perception. On the Coriolis Acceleration Platform of the Naval Aerospace Medical Research Laboratory (NAMRL), five adult male subjects were oscillated in the lateral direction (Y-axis, subject either sitting 'upright' or 'supine') and in the longitudinal direction (Z-axis, subject 'supine' or on his right side). A fifth condition, in which the subject was oriented 'upright' facing the direction of oscillation (X-axis), served as a control condition. In separate sessions, the same subjects were also rotated in these five orientations. Data were obtained by measuring ocular torsion with video-oculography, and the direction of the subjective vertical was recorded by means of a joystick. The sinusoidal oscillations were at 0.22, 0.3, 0.4, and 0.5 Hz, with maximum amplitude of 0.5 g. Rotations were at 17 feet from center at 57 deg/S, which resulted in a centripetal force of 0.5 G on the head. Ocular torsion appeared in all four main conditions (acceleration in Y and Z), but with a significant difference in amplitude. No torsion was found in the control condition (acceleration in X), as was expected. The subjects experienced tilt under centrifugation, and indicated a so-called 'hilltop illusion' during oscillation. The experience of tilt and ocular torsion were most prominent at the lower oscillation frequencies.

Descriptors :   *SPATIAL DISTRIBUTION, *STIMULATION(PHYSIOLOGY), *ACCELERATION, *VISION, *EYE, *TORSION, *VESTIBULAR APPARATUS, *EYE MOVEMENTS, HUMANS, ORIENTATION(DIRECTION), LINEARITY, MALES, AMPLITUDE, OSCILLATION, LOW FREQUENCY, PERCEPTION, TILT.

Subject Categories : Anatomy and Physiology
      Stress Physiology

Distribution Statement : APPROVED FOR PUBLIC RELEASE