BISTABILITY & HYSTERESISIN SUBJECTIVE VERTICAL

Bram Bielen

Natuurwetenschappen

Ministage (40 dagen)

Subjective Visual Vertical (SVV)

What is up?

Systematic error in visual verticalclassic 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

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

Dynamic experiments

• Subject is rotated for two full cycles 720o

CW or CCW.

• Testing during rotation.

• Stimulus at 3 sec interval

Dynamic test result

Bistability

Bistability

• Two types of response possible

• At larger tilt angles

Bistability illustrated

18090 2700 360

o A-cluster

Δ E-cluster

Hysteresis

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 resultsContinuous Limited

Static resultsContinuous Limited

Static resultsContinuous Limited

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?