The purpose of this study is to determine whether a perceptual procedure detect unilateral labyrinthine disturbance. This work derives from previous studies to determine "point of subjective equality" between discrepant inertial and visual motion cues. (Prothero JD, Parker DE. A unified approach to presence and motion sickness. In Virtual and Adaptive Environments: Psychological and Human Performance Issues, Haas MW, Hettinger LJ, eds. Mahwah, New Jersey: Lawrence Erlbaum Associates, In press; Carpenter-Smith TR, Futamura RG, Parker DE. Inertial acceleration as a measure of linear vection: An alternative to magnitude estimation. Perception & Psychophysics, 1995,57,35-42.)
PROCEDURE
Subjects oscillated about earth-vertical axis at 0.1 hz; peak angular velocities of 5 -35 /s.
Subjects look at a visual scene, which also rotates, on a head-mounted display. Chair and visual scene motion either in phase or 270 out of phase
Subjects move a switch to the left when they perceive that they change direction from left to right and to the right when they change direction from right to left
54 Y.O. MALE WITH UNILATERAL DAMAGE
SUBJECT GROUP DIRECTION INDEX
MA NORM NONE 0.50
JD NORM L 0.64
JJ NORM L 0.67
SP NORM R 0.67
JP NORM R 0.67
HP NORM R 0.64
JPR NORM R 0.54
AS NORM R 0.69
DS NORM L 0.90
DW NORM L 0.67
AW ULD L 0.92
So far, preliminary observations support the view that cross-over procedure may permit assessment of unilateral damage. Also, a potential advantage of cross-over procedure is that assessment is not restricted to horizontal canals (unlike caloric testing).