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VESTIBULAR SIGNALS Jan Van Gisbergen

VESTIBULAR SIGNALS Jan Van Gisbergen. PhD COURSE SENSORY SYSTEMS Utrecht, September 29, 2008. detection of self motion sensing body orientation in space visual perception in earth-centric coordinates. SCOPE.

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VESTIBULAR SIGNALS Jan Van Gisbergen

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  1. VESTIBULAR SIGNALSJan Van Gisbergen PhD COURSE SENSORY SYSTEMS Utrecht, September 29, 2008

  2. detection of self motion sensing body orientation in space visual perception in earth-centric coordinates

  3. SCOPE • Functions and limitations of vestibular sensors • Ambiguity problem of the otoliths • Solution to the ambiguity problem • Visual-vestibular fusion • Transformations from head to body reference frame • Visual space perception in static tilt • Bayesian model

  4. MULTISENSORY INTEGRATION

  5. VESTIBULAR SENSORSfunctions &limitations

  6. VESTIBULAR SENSORS canals otoliths

  7. SEMICIRCULAR CANALS measure head rotation

  8. CANAL GEOMETRY Three perpendicular canals measure head rotation in 3 dimensions

  9. BEST ROTATION AXES a = anterior canal p = posterior canal h = horizontal canal rotation in direction of arrow excites afferents from a given canal

  10. BEST ROTATION AXIS OF CANAL AFFERENT Yakushin (2006) JNP

  11. OPTIMAL ROTATION AXES OF CANAL AFFERENTS

  12. DYNAMICS OF CANAL SIGNALS Insensitive to low-frequency rotations (high pass filter) • Canal afferent fiber in 8th nerve • High resting discharge • Codes cupula deviation

  13. CONSTANT ROTATION IN DARKNESS • rotation percept decays • after stop, percept of rotation in opposite direction • reflects cupular mechanics

  14. OTOLITHS sensitive to linear acceleration during translation and to tilt, due to the pull of gravity

  15. HAIRCELL ACTIVATION • each haircell is connected to separate nerve fiber • deflecting cilia toward kinocilium depolarizes haircell

  16. POLARISATION VECTOR tilt stimuli: nose down left ear down nose up each otolith cell has cosine tuning: indicates head orientation where pull of gravity has maximum effect Eron et al. (2008) J. Neurophysiol.

  17. OTOLITHS sensitive to tilt and translation

  18. POLARISATION VECTORS Fernandez and Goldberg (1976) JNP

  19. AMBIGUITY PROBLEMOF THE OTOLITHS

  20. OTOLITH SIGNAL IS AMBIGUOUS hair cellscannot distinguish tilt and translation

  21. SOMATOGRAVIC ILLUSION pilot is upright, but feels tilted (only in darkness)

  22. AMBIGUITY PROBLEM inverse problem • otolith signal may have various causes: • translation (a) • force of gravity due to tilt (g) • combination of a and g • How can the brain resolve this ambiguity ?

  23. CANAL- OTOLITH INTERACTION MODEL • canals detect rotation during tilt changes • their signal helps to decompose otolith signal Angelaki et al. (1999)

  24. CANAL–OTOLITH INTERACTION MODEL tilt angle linear acceleration angular velocity • basic principle: • tilt stimulates otoliths AND canals • - translation stimulates only otoliths Merfeld and Zupan (2002) J. Neurophysiology

  25. TESTING THE MODEL percepts during rotation about a tilted axis (OVAR) Vingerhoets et al. (2006) J. Neurophysiol. Vingerhoets et al. (2007) J. Neurophysiol.

  26. THE ACTUAL MOTION - rotation about tilted axis - in darkness - constant velocity

  27. MODEL PREDICTIONS rotation signal decays gradually wrong interpretation otolith signal: illusory translation percept

  28. SCHEMATIC SUMMARY OF RESULTS Actual motion: rotation percept Percept: translation percept confirms prediction

  29. TRANSLATION AND ROTATION PERCEPT DATA rotation percept translation percept

  30. VISUAL – VESTIBULAR FUSION

  31. FUSION OF VISUAL AND VESTIBULAR SIGNALS FOR DETECTION OF EGOMOTION • brain interprets whole field motion as due to egomotion • can detect constant velocity motion (low pass) • complements vestibular motion detection (high pass)

  32. CANALS ARE HIGH PASS

  33. ROTATION IN LIGHT: VISUAL CONTRIBUTION • Rotation percept in the light is veridical • Visual system detects low frequencies • Canals detect high frequencies circular vection

  34. CONVERGENCE IN VESTIBULAR NUCLEUS visual system detects low frequencies canals detect high frequencies

  35. OPTIC FLOW PROVIDES LOW FREQUENCY INPUT FROM LINEAR MOTION • otoliths detect linear acceleration • optic flow can induce linear egomotion (train illusion!!)

  36. TRANSFORMATIONS FROM HEAD TO BODYREFERENCE FRAME

  37. BALANCE • Otoliths measure head position in space • To maintain balance, we must know body position in space • Which mechanisms areinvolved?

  38. BALANCE • Measure head position in space (HS) • Measure position head on trunk (HB) • Compute position of body in space (BS): • BS = HS - HB

  39. EFFECT OF ELECTRICAL OTOLITH STIMULATION • experiment in darkness • results in body tilt • Why? • HS changes • HB is not changed • BS changes, subject corrects • BS = HS - HB

  40. VESTIBULAR - NECK PROPRIOCEPTIVE INTERACTIONS monkey moves on sled in various directions cell recording in cerebellum (FN) neuron b codes linear motion in body-centered reference frame (accounts for neck signals) neuron c codes motion in head-reference frame Angelaki (2008) Ann Rev Neuroscience

  41. VISUAL SPACE PERCEPTION IN STATIC TILT

  42. VISUAL VERTICAL • How can we determine the orientation of visual objects relative to the direction of gravity, even when we are tilted in darkness? • What is the role of the vestibular system?

  43. SENSING THE DIRECTION OF GRAVITY experiments in darkness • Two different tasks: • Set line to vertical (SVV) • Estimate your body tilt (SBT) Van Beuzekom & Van Gisbergen (2000) J. Neurophysiol. Van Beuzekom et al. (2001) Vision Res. Kaptein & Van Gisbergen (2004, 2005) J. Neurophysiol. De Vrijer et al. (2008) J. Neurophysiol.

  44. ACCURACY vs PRECISION Accuracy: How close is the response to the true value? Precision: How reproducible is the response? darts analogy:

  45. ACCURACY AND PRECISION IN LINE TASK (SVV) accuracy precision De Vrijer et al. (2008) J. Neurophysiol. De Vrijer et al. (2008) in progress

  46. ACCURACY IN LINE TASK due to underestimation of body tilt?

  47. NO UNDERESTIMATION OF BODY TILT SVV SBT • Subjects know quite well how they are tilted (SBT) • Yet, their line settings undercompensate for tilt (SVV) Van Beuzekom et al. (2001) Vision Res. Kaptein and Van Gisbergen (2004) J. Neurophysiol.

  48. PRECISION IN LINE TASK is scatter in SVV simply reflection of noise in body tilt signal? De Vrijer et al. (2008) J. Neurophysiol. De Vrijer et al. (2008) in progress

  49. SVV LESS NOISY THAN SBT psychometric experiments at 0o and 90o tilt: De Vrijer et al. in progress

  50. SVV LESS NOISY THAN SBT

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