Affiliations: Department of Mathematics and Statistics, Colby College, Waterville, ME, USA | Man Vehicle Laboratory, Massachusetts Institute of Technology, Cambridge, MA, USA
Correspondence:
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Corresponding author: Jan E. Holly, Department of Mathematics and Statistics, Colby College, 5845 Mayflower Hill, Waterville, ME 04901 USA. Tel.: +1 207 859 5845; Fax: +1 207 859 5846; E-mail: jeholly@colby.edu
Note: [1] This paper was presented at the Session: Spatial Orientation at the 8th Symposium on the Role of the Vestibular Organs in Space Exploration, April 8–10, 2011, Houston, TX, USA
Abstract: Perceptual disturbances and motion sickness are often attributed to sensory conflict. We investigated several conditions: head movements in microgravity, periodic motions in 1-g, and locomotion with vestibular disorders. In every case, linear vectors such as linear and gravitational acceleration are crucial factors, as previously found for head movements in artificial gravity, and thus the importance of measuring linear vectors emerges as a common theme. By modeling the sensory conflict between the vestibular and somatosensory systems, we computed a measure of linear conflict known as the "Stretch Factor". We hypothesized that the motions with the greatest Stretch Factor would be the most provocative motions. Results: For head movements in microgravity, the Stretch Factor can explain why fast movements are more provocative than slow movements, and why pitch movements are more provocative than yaw movements. For off-vertical-axis rotation (OVAR) in 1-g, the Stretch Factor predicts that the most provocative frequency is higher than that for vertical linear oscillation (VLO). For example, the same sensor dynamics can predict a most provocative frequency around 0.2 Hz for VLO but 0.3 Hz for OVAR, solving a mystery of this experimentally observed discrepancy. Finally, we determined that certain sensory conflict perceptions reported by vestibular patients could be explained via mathematical simulation.
