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. (Underestimation of body tilt).

Müller effect (E-effect) SVV deviates in the direction of feet tilt. (Overestimation of body tilt).

Effects illustrated

ClockWise (CW) & CounterClockWise (CCW) CWCCW (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 720 o CW or CCW. Testing during rotation. Stimulus at 3 sec interval

Dynamic test result

Bistability

Two types of response possible At larger tilt angles

Bistability illustrated o A-cluster Δ E-cluster

Hysteresis

Response depends on direction of preceding rotation LP & SP

Hysteresis illustrated

Research

Why? Different results dynamic and static experiments

Test Paradigm Continuous & limited static dynamic

Task What is the orientation of a line?

Static results ContinuousLimited

Static results ContinuousLimited

Static results ContinuousLimited

Dynamic results + CCW o CW

Dynamic results + CCW o CW

Conclusions Verification of bistability and hysteresis Bistability in dynamic data

What to do? More subjects Different angles Other paradigms Bayesian model

Any questions?