SELF-MOTION PERCEPTION: ASSESSMENT BY REAL-TIME COMPUTER-GENERATED ANIMATIONS OVERALL GOAL: PERCEPTUAL TESTS FOR VESTIBULAR FUNCTION A NEW PROCEDURE FOR SELF-MOTION ASSESSMENT WHY STUDY PERCEPTION? DISCREPANCIES BETWEEN EYE MOVEMENT RESPONSES AND SELF-MOTION PERCEPTION, ESPECIALLY DURING ADAPTATION POSSIBLE ADVANTAGES OF ANIMATIONS TO STUDY SELF-MOTION PERCEPTION DON’T NEED WORDS SELF-MOTION OCCURS WITH 6 DOF (COMPLEX SELF-MOTION MAY BE EVOKED BY SIMPLE STIMULATION) BODY IS AN ARTICULATED SYSTEM (BODY PARTS MAY MOVE RELATIVE TO ONE ANOTHER) VISUAL SCENE AND SELF MAY MOVE DIFFERENTLY ANIMATIONS STUDY PROCEDURE STIMULUS: CROSS-COUPLED ANGULAR ACCELERATION (HEAD ROLL DURING EARTH-VERTICAL ROTATION) SUBJECTS MANIPULATE REAL DOLL’S HEAD SO THAT THE VIRTUAL DOLL’S HEAD DISPLAYED ON MONITOR MOVES IN MANNER THAT CORRESPONDS TO PERCEIVED HEAD MOTION (MAGNETIC FIELD TRACKER EMBEDDED IN REAL DOLL’S HEAD) ANIMATIONS RECORDED FOR LATER ANALYSIS RECORD VERTICAL EYE MOVEMENTS (EXPERIMENT 3) RESULTS: EXPERIMENTS 1 AND 2 PERCEIVED PITCH HEAD DIRECTIONS DID NOT CORRESPOND TO PREDICTIONS EXPERIMENT 1 STIMULUSEXPECTED PERCEPTION %OBSERVED ROTATION DIRECTION /HEAD ROLL DIRECTION CW-R / CCW-LREARWARD 76% CCW-R / CW-LFORWARD 38% EXPERIMENT 2 CW-R / CCW-LREARWARD 54% CCW-R / CW-LFORWARD 33% EXPERIMENT 3: EYE MOVEMENTS RESULTS: EXPERIMENT 3 SLOW PHASE EYE MOVEMENT DIRECTIONS CORRESPONDED TO PREDICTIONS; BUT PERCEIVED PITCH HEAD DIRECTIONS DID NOT STIMULUS EXPECTED %OBSERVED EXPECTED %OBSERVED PERCEPTION SLOW-PHASE ROTATION DIRECTION DIRECTION -HEAD ROLL DIRECTION CW-R / CCW-LREARWARD38%DOWN96% CCW-R / CW-LFORWARD22%UP100% CONCLUSIONS OUR NON-VERBAL PERCEPTUAL REPORTING PROCEDURE SUPPORTS SELF-MOTION PERCEPTION REPORTING. PERCEPTUAL REPORTS DID NOT CORRESPOND TO EXPECTATIONS BASED ON MECHANICAL STIMULI TO VESTIBULAR APPARATUS AND PREVIOUS REPORTS (GUEDRY & MONTAGUE, 1961; GUEDRY, 1974). DIFFERENCES BETWEEN THE RESULTS OF THE PRESENT STUDY AND PREVIOUS ONES MAY BE DUE TO SUBJECTS’ TRAINING AND EXPECTATIONS. OUR EYE MOVEMENT DATA SUPPORT THOSE REPORTED BY GUEDRY AND MONTAGUE. This project is sponsored by: NASA Grants NAG and D.E. Parker and J.O. Philips: Department of Otolaryngology - HNS and HTIL, University of Washington Fig. 1. Illusory self-motion was produced by head roll during yaw axis, earth-vertical rotation. For leftward head roll during counter-clockwise rotation, illusory rearward head pitch and downward slow phase eye movements would be expected. Fig. 2. 2A. Selected frames from animation. Stimulus: head roll from right to left during CCW rotation. The real leftward head roll accompanied by illusory forward head pitch; as the roll motion was completed, brief leftward yaw was recorded. The subject reported verbally that her head went “forward and then slight rotation.” 2B. “Pitch”, “roll” and “roll” path signals (ordinate) as a function of frame (24 frames / s). Frames illustrate leftward head roll which was accompanied by forward pitch (frames 15-50). Leftward head yaw is illustrated in frames Fig. 3. Four-second segment of EOG for Subject 3, Trail 1. Chair rotation was counter-clockwise (viewed from above). At time 57.7, the subject rolled her head from her right to her left shoulder (indicated by step function). Slow-phase down nystagmus appeared after about 1.3 s. Slow-phase direction was as predicted.