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BISTABILITY & HYSTERESIS IN SUBJECTIVE VERTICAL. Bram Bielen Natuurwetenschappen Ministage (40 dagen). Subjective Visual Vertical (SVV). What is up?. Systematic error in visual vertical classic interpretation. Aubert effect (A-effect). SVV deviates in the direction of head tilt.
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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