vestibular contributions to visual stability ronald kaptein & jan van gisbergen colloquium...
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Vestibular contributions to visual stability
Ronald Kaptein & Jan van Gisbergen
Colloquium MBFYS, 7 november 2005
Visual stability
Introduction
maintaining a roughly veridical percept of allocentric visual orientations despite changes in head orientation.
Visual stability
Introduction
Different sources of information:
•Visual•Somatosensory•Auditory•Proprioceptive•Vestibular
Visual stability
Introduction – visual stability
Visual stability
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2
Introduction – visual stability
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Subjective visual vertical
Sudden transition at large tilt:
Introduction - SVV
Subjective visual vertical
Introduction - SVV
Errors in subjectivevisual vertical
Errors in subjectivebody tilt
-=cw-=ccw
Subjective visual vertical
Introduction - SVV
Subjective visual vertical
Introduction - SVV
* Kaptein & Van Gisbergen, J Neurophysiol, 2004* Kaptein & Van Gisbergen, J Neurophysiol, 2005
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2
Vestibular processing
Introduction
Vestibular system
Introduction
Canals + Otoliths
Semicircular canals
Introduction
Limitations: poor response to constant-velocity and low-frequency rotations (i.e a high-pass filter)
Otoliths
Introduction
Limitations: cannot discriminate between tilt and translation (ambiguity problem)
Otoliths
Introduction
Ambiguity problem:
Neural strategies for otolith disambiguation:• Frequency segregation model• Canal-otolith interaction model
Frequency-segregation model
Introduction
Based on the constant nature of gravity and the transient nature of acceleration
Canal-otolith interaction model
Introduction
Head tilt leads to a canal signal, head acceleration does not
Questions
Introduction
• How good is visual stability during head rotations in the dark? • What is the role of canal and otolith signals in this process?• How can the processing of canal and otolith signals be modeled?
METHODS
Methods – Task 1
Vestibular rotation
Methods
G
Upright: canals+otoliths
Supine: canals only
Sinusoidal rotationAmplitude: 15°Frequencies: 0.05, 0.1, 0.2 & 0.4 Hz
TASK 1
Results
Task 1
Methods
While rotating, subjects judged the peak-peak sway of various luminous lines which counter rotated relative to the head, at different amplitudes.
Task 1
Methods
Not enough counter rotation:
Too muchcounter rotation:
Task 1
Methods
Updating gain (G): the amount of counter rotation necessary for perceptual spatial stability, expressed as a fraction of head-rotation amplitude.
G=0 : No updating (Head-fixed line is perceived as stable in space)G=1 : Perfect updating
RESULTS 1
Methods – Task 1
Raw data task 1
Results – Task 1
1 subject,upright
Results – Task 1
Updating gain
no updating
perfect updating
DISCUSSION 1
Discussion – Task 1
2
Interpretation task 1
Discussion – Task 1
Interpretation task 1
Discussion – Task 1
Interpretation task 1
vestcompvorS
H GGGH
LG
SL
1
0ˆ
Discussion – Task 1
updating gain:
otoliths+canals canals
Otolith & canal contributions
Discussion – Task 1
Otolith & canal contributions
canals
otoliths
improvement in upright, due to gravity, is low-pass:
Discussion – Task 1
canal-otolith interaction
frequency segregation
Can current models explain our results?
Not straightforward:both models predict low-pass characteristics in upright condition.
Discussion – Task 1
Linear-summation model for rotational updating
Discussion – Task 1
Linear-summation model
Interaction model:
Filter model:
Discussion – Task 1
Fits of linear-summation model
upright
supine
upright
supine
Interaction model
Filter model
R2adj=0.72 R2
adj=0.82
Discussion – Task 1
TASK 2
Methods – Task 2
Task 2
Methods – Task 2
While rotating, subjects judged the side-to-side displacement of various LEDs which were stable relative to the head or stable in space.
Task 2
Methods – Task 2
Task 2
Updating gain (G): the amount of counter rotation necessary for perceptual spatial stability, expressed as a fraction of head-rotation amplitude.
Perceived translation (T): the perceived spatial displacement of an LED situated on the rotation axis.
Methods – Task 2
RESULTS 2
Results – Task 2
Raw data task 2
Results – Task 2
1 subject,upright
Results – Task 2
Updating gain
no updating
perfect updating
Results – Task 2
Perceived translation
DISCUSSION 2
Discussion – Task 2
Discussion – Task 2
GIF Resolution
Further processing necessary
Discussion – Task 2
Translation predictionsusing perfect integration
Discussion – Task 2
Canal-otolith interaction
Frequency segregation
Discussion – Task 2
Translation predictionsusing leaky integration
CONCLUSIONS
Conclusion
Conclusions
Q: How good is visual stability during head rotations in the dark?
A: • Compensation for rotation is only partial but better for higher frequencies. • Small illusionary translation percepts in upright condition at highest frequencies.
Conclusion
Conclusions
Q: What is the role of canal and otolith signals in maintaining visual stability?
A: • Both otoliths and canals contribute to rotational updating. • Illusionary translation percept is otolith driven
Conclusion
Conclusions
Q: How can the processing of canal and otolith signals be modeled?
A: • Rotation: Linear summation of canal and otolith cues.• Translation: Double leaky integration of internal estimate of acceleration.• We are not yet able to discriminate between the two disambiguation schemes
Conclusion
Questions?
Conclusion