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

1

2

Introduction – visual stability

?

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

1

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