1 What’s the Relationship between Self-Motion Perception and Motion Sickness? L. Scott Urmey Mary E. English Andre McCrimmon *Stephen A. Palmisano Frederick Bonato Andrea Bubka Saint Peter’s College * University of Wollongong
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What’s the Relationship between Self-Motion Perception and Motion Sickness?
L. Scott Urmey
Mary E. English
*Stephen A. Palmisano
Saint Peter’s College
*University of Wollongong
Under optokinetic drum conditions, a stationary participant views the patterned interior of a rotating drum and perceives illusory self-motion and sometimes motion sickness. But how exactly are vection and MS related? Experiments using tilted drums and results obtained by others suggest that vection per se does not cause motion sickness. Only Changes in vection velocity and/or heading lead to motion sickness because the sensory conflict is increased only when velocity and/or heading changes occur.
EPA, 2005Boston, MA
A large drum (cylinder) that rotates around a stationary observer
Phenomena Associated with Optokinetic Drums
Vection (illusory self-motion)- Usually within 30 seconds observers experience vection (Fischer & Kornmüller, 1930; Tschermak, 1931) in the direction that is opposite to the drum’s true physical rotation. Vection is the self-motion perception that often occurs when a large portion of an observer’s visual field moves. Vection is a useful tool for studying visual field characteristics that affect self-motion perception.
Motion Sickness- When optokinetic drum viewing is extended (several minutes) many observers experience motion sickness symptoms. Although motion sickness is commonly associated with passive travel (e.g., carsickness, seasickness, airsickness), stimulus conditions that evoke illusory self motion (e.g., virtual environments, optokinetic drums, large screen cinemas) can also result in motion sickness (e.g., simulator sickness, cybersickness). Motion symptoms can include but are not limited to: dizziness, headache, spinning (vertigo), bodily warmth, increased salivation, stomach awareness, nausea, and dry mouth.
0% lever pressure
100% lever pressure
Degree of experienced vection, which was recorded for both halves of each trial, was indicated by pressing a lever. As the magnitude of perceived vection increased, the lever was pushed forward. Pressure on the lever was directly recorded by computer for later analysis.
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Sample output from lever device for measuring vection
Measuring Motion Sickness (MS)
The symptoms included spinning, dizziness, headache, increased salivation, bodily warmth, stomach awareness, nausea, and dry mouth. Each symptom was rated on a 0-3 scale (0=none, 1=slight, 2=moderate, 3=severe) every two minutes throughout a 16 minute trial. A SSMS (subjective symptoms of motion sickness) composite score was obtained by adding up the ratings for all eight symptoms.
Tilted Drum Experiment
Hypothesis:Changes in vection due to tilt will lead to a faster onset of MS compared to a drum that rotates on an earth vertical axis.
Twelve observers, within-subjects design, drum velocity = 10 rpm, 24 pairs of black and white vertical stripes, independent variable: 0 degree, 5 degree, 10 degree tilt, dependent variable: SSMS (0-3) on 8 symptoms
Minutes of drum exposure
Results and Discussion
Increasing drum tilt did not affect vection (spinning) ratings. However, the fastest onset of
symptoms occurred in the tilt conditions (p<.01). Sensory conflict was the most extreme in
the 10 degrees tilt condition. In other words, the 10 degree condition should have resulted
in the most disparity between vestibular and visual sensory inputs.These results suggest
that an increase in sensory conflict, not vection, are what cause cybersickness to occur in
optokinetic drums.These results can be explained in terms of a mismatch between sensed
vertical and expected vertical (Bles, Bos, de Graaf, et al., 1998) they can also be
explained in terms of a mismatch between sensed inertia and expected inertia. However,
the results of the changing rotation direction experiment can only be explained in terms of
a mismatch between sensed and expected inertia. The next experiment was designed
to test if a mismatch between sensed and expected inertia alone would lead MS.
Changing Rotation Direction Experiment
Hypothesis:Changes in vection due to rotation direction change will lead to a faster onset of MS compared to a drum that rotates in the same direction. The rationale for this hypothesis is based on the idea that a mismatch between sensed and expected inertia alone can lead to MS.
Twelve observers, within-subjects design, drum velocity = 5 rpm, 6 pairs of black and white vertical stripes, independent variable: rotation direction, dependent variable: SSMS (0-3) on 8 symptoms
Minutes of drum viewing
Results and Discussion
Symptoms occur significantly faster in the changing direction condition (p<.01).
Sensory conflict was the most extreme in the changing direction condition. If actual
(physical) self-rotation changes took place the vestibular system would respond because
of inertia. Results support sensory conflict theory but not subjective vertical mismatch
theory. What is happening in terms of vection?
General Discussion and Conclusions
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saturated vection saturated
less changing vection and less sickness
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more changing vection and more sickness
Supported by National Science Foundation Grant BCS-0002620