Tilt perception during rotation about a tilted axis Rens Vingerhoets 1,2 Jan Van Gisbergen 1
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Transcript of Tilt perception during rotation about a tilted axis Rens Vingerhoets 1,2 Jan Van Gisbergen 1
Tilt perception during rotation about a tilted axis
Rens Vingerhoets1,2
Jan Van Gisbergen1
Pieter Medendorp2,3
1. Department of Biophysics2. Nijmegen Institute for Cognition and information3. FC Donders Centre for Cognitive Neuroimaging
Spatial orientation
• Visual Cues
• Vestibular System
• Somatosensory Cues
Introduction - Sensors
{Semi-circular canals
Otoliths
Introduction - Sensors
The semi-circular canals
• Sensitive to rotation (angular acceleration)
Introduction - Sensors
The otoliths
• Sensitive to acceleration caused by:– Gravity (Tilt)– Inertial acceleration (Translation)
Signal is ambiguous}
Tilt Translation
Introduction - Sensors
How is the otolith ambiguity resolved?
Hypothesis: canal-otolith interaction
Tilt
Angularvelocity
Tilt + Translation
Rotation
Otoliths
Canals
g
a
^
^
ω̂
Internal Model Translation
Rotation about a tilted axisRotation about a vertical axis
Introduction
What is rotation about a tilted axis (OVAR)?
What causes this illusory translation percept?
Introduction
What happens during OVAR?
Otolith signal from tilt misinterpreted as translation?
Left Ear Down(LED)
Right Ear Down(RED)
Nose Up(NU)
Nose Down(ND)
Veridical motion percept
0 30 60 90 120
Time (s)
Ro
tatio
n p
erc
ep
t
Time (s)
LEDRED
NU
R
Illusory motion percept
LED
ND
NU
RED
ND
0 30 60 90 120
Tra
nsl
atio
n p
erc
ep
t
Introduction – Otolith Disambiguation
The model predicts a gradually increasing underestimation of tilt during OVAR
0 30 60 90 120
0
10
20
3030o/s & 45o
Tilt
und
eres
timat
ion
(deg
)
0 30 60 90 120
50o/s & 45o
Time (s)
0 30 60 90 120
50o/s & 15o
Introduction – research question
• Is there evidence for the underestimation of tilt predicted by the canal-otolith interaction model?
• If so, is the time course compatible with canal-signal delay?
Methods
Experimental setup
- Vestibular chair -
Introduction – Subjective Visual Vertical
Tilt perception tested with Subjective Visual Vertical (SVV)
Gravity
Flash!Clockwise
Methods
Experimental setup • 6 subjects • 3 dynamic conditions
- Large tilt & Low speed (45o tilt and 30o/s)- Large tilt & High speed (45o tilt and 50o/s)- Small tilt & High speed (15o tilt and 50o/s)
• Each dynamic condition consisted of 20 runs of 120 s each
• In each LED and RED phase flashed presentation of oriented line
• Subjects used a toggle switch to indicate whether the line had to be more clockwise/counterclockwise to be perceived as earth-vertical
• Time course of SVV determined using an adaptive staircase over runs.
• 2 static conditions: 45o tilt and 15o tilt
Results
Results – Dynamic paradigm
Dynamic results of 1 subjectE
rror
in S
VV
, γ (
deg)
0 30 60 90 120
-30
-20
-10
0
10
20
30
30o/s & 45o
0 30 60 90 120
Time (s)
0 30 60 90 120
50o/s & 45o 50o/s & 15o
Results – Dynamic paradigm
Dynamic results
- Time course of SVV shows gradually increasing underestimation of tilt, just as canal-otolith interaction model predicts
- Initial responses are already biased.
Results – Static paradigm
Results of static tilt
-10
0
10
45o
tilt
Err
or
in S
VV
se
ttin
g (
γ),
(de
g)
-10
0
1015
o tilt
JG NK MV RV SP TG
LED
RED
Tilt underestimation
Tilt overestimation
Tilt underestimation
Tilt overestimation
Results – Dynamic paradigm
Dynamic results
Is the dynamic response pattern simply a linear combination of static effects and canal-otolith interaction?
SVV = A • Dynamic + B • Static
Results – Dynamic paradigm
Fit to dynamic results of 1 subjectE
rror
in S
VV
, γ (
deg)
0 30 60 90 120
-30
-20
-10
0
10
20
30
30o/s & 45o
0 30 60 90 120
Time (s)
0 30 60 90 120
50o/s & 45o 50o/s & 15o
A=1.3 B=0.8
Results – Dynamic paradigm
Coefficients of all subjects
SVV = A • Dynamic + B • Static
-0.5
0
0.5
1
1.5
2
2.5
JG NK MV RV SP TG JG NK MV RV SP TG
A B
Results – Dynamic paradigm
Model predicts dynamic SVV
0 30 60 90 120
-15
0
15
30
Dyn
amic
res
pons
e E
rror
, γ (
deg)
0 30 60 90 120Time (s)
0 30 60 90 120-30
Model Prediction
Pooled dynamic response
30o/s & 45o 50o/s & 45o 50o/s & 15o
Conclusions
Conclusion
• Static effects also play a role in dynamic conditions
• Canal-otolith interaction can account for dynamics of tilt percept
Otoliths
Canals
Internal Model
Tilt
Angularvelocity
Tilt
Translation
Rotation
The End