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This study by Bram Bielen explores the effects of head and feet tilt on Subjective Visual Vertical (SVV). Discover the Aubert and Müller effects and how SVV deviates with head and feet tilt direction. Dynamic and static experiments, hysteresis illustrated, and recommendations for future research included.
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BISTABILITY & HYSTERESISIN SUBJECTIVE VERTICAL Bram Bielen Natuurwetenschappen Ministage (40 dagen)
Subjective Visual Vertical (SVV) What is up?
Aubert effect (A-effect) SVV deviates in the direction of head tilt. (Underestimation of body tilt).
Müller effect (E-effect) SVV deviates in the direction of feet tilt. (Overestimation of body tilt).
ClockWise (CW) & CounterClockWise (CCW) CCW CW (ρ) Rear View
Task • Adjustment, what is vertical?
Static experiments • Subjects are rotated to an angle (ρ) between 0 and 360º, CW or CCW. • Testing begins after final tilt angle is reached. • Examples: 30 sec / 60 sec.
Typical static test result * CW O CCW
Dynamic experiments • Subject is rotated for two full cycles 720o CW or CCW. • Testing during rotation. • Stimulus at 3 sec interval
Two types of response possible At larger tilt angles Bistability
Bistability illustrated o A-cluster Δ E-cluster 0 90 180 270 360
Hysteresis • Response depends on direction of preceding rotation • LP & SP
Why? • Different results dynamic and static experiments
Test Paradigm • Continuous & limited static • dynamic
Task • What is the orientation of a line?
Static results Limited Continuous
Static results Limited Continuous
Static results Limited Continuous
Dynamic results o CW + CCW
Dynamic results o CW + CCW
Conclusions • Verification of bistability and hysteresis • Bistability in dynamic data
What to do? • More subjects • Different angles • Other paradigms • Bayesian model