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Thomas Haarmeier, Peter Thier, Marc Repnow & Dirk Petersen*

False perception of motion in a patient who cannot compensate for eye movements (Oct 1997 Nature). Thomas Haarmeier, Peter Thier, Marc Repnow & Dirk Petersen*. We usually unaware motion of an image across retina that results from our own movement. We perceive a stable world

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Thomas Haarmeier, Peter Thier, Marc Repnow & Dirk Petersen*

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  1. False perception of motionin a patient who cannot compensate for eyemovements (Oct 1997 Nature) Thomas Haarmeier, Peter Thier, Marc Repnow & Dirk Petersen*

  2. We usually unaware motion of an image across retina that results from our own movement. • We perceive a stable world e.g. Slow-tracking  see a stable world Dr. Joe’s example, tapping one eye. • Why?  Von Helmholtz’s suggestion Object motion = internal reference signal - retinal motion signal (Anatomical underpinning unknown? By the time of 1997) A stationary world?

  3. 35-year-old, male • Admitted to hospital in Aug 1996 • Slight visual acuity reduction  left 0.8 vs. right 1.0(Had a mild strabismus, surgically corrected in Aug 1995) • > 6 years vertigo & nausea when eyes: •  tracking moving objects OR •  fixed on stationary object during ego-motion • No vertigo & nauseawhen eyes closed • Ego-motion (e.g. watching obj thru the window of a moving car). SUBJECT -- R.W.

  4. Facts suggesting a longer time deficit: • Childhood: Striking insufficiency in ball games • But, above-average results in athletics • Failed to acquire a driver’s license for insecure in judging object speed or distance at high speed. • ∴ Deficit in: • Goal-directed eye movements • The consequent need to handle self-induced retinal image slip. SUBJECT -- R.W.

  5. Excluding other common causes of vertigo: • No asymmetry in response & normal vestibulo-ocular reflex. • Pursuit eye movements, saccades and optokinetic nystagmus were intact. • No electrophysiological correlate of vestibular epilepsy SUBJECT -- R.W.

  6. MRI IMG -1  Bilateral extrastriate lesion

  7. A small question in BV MRI IMG -2  Bilateral extrastriate lesion

  8. Vertigo was selectively related to the processing of visual motion induced by ego-motion. (not pursuit?) Tests: Filehne illusioncoherent motion stimulistatic and dynamic visual acuitydetection of velocity steps Hypothesis

  9. Def: illusionary background motion induced by pursuit eye movements • Design • Red dot (10mm, 300ms) v = constant, move 30 deg from middle to the right • Back ground of white dots(15mm) • Report the direction of perceived background motion • PPS  background velocity that resulted in 50% left & 50% right response after repeated presentation Test of Filehne illusion

  10. Test of Filehne illusion

  11. R.W. perceived motion reflects image movement on the retina. • R.W. is deprived of a sense of stationarity unless the background image is stabilized to some degree on his retina.

  12. Two fields: borderless 12 X 12 deg square, 1 coherent, 1 non-coherent motion • Large number of dots: 400 in each field (d=7mm, v = const) • Short dot lifetime: 100 ms • Task: to discriminate filed 1 from field 2 by determining min % of coherently moving dots. • Threshold: 75% correct. Coherent motion stimuli

  13. Coherent motion

  14. Successfully detected Suggested unimpaired coherent motion detection v = 6deg/s Presentation t = 200ms

  15. Stationary acuity (Landolt Cs optotypes) Luminance 60 cd/m2, 500 ms stationary local background 250 ms Landolt C • Dynamic acuity Local background moving rightward Landolt C added in the movement (250ms) Threshold: 75% correct • Result: unimpaired detection of 2D shape in motionExcellent acuity for moving & stationary Landolt target (binocular 1.0) Static & Dynamic visual acuity

  16. Required to track a moving target • Target started to move rightward, v1 = const • Change to v2 after interval ≥ 800ms • Continued moving for 500 ≤ t ≤ 1400 ms • Report whether v1 ≥v2 or v1 ≤v2 Detection of velocity steps

  17. Generate smooth eye movements to compensate for target motion. • R.W.’s Acceleration & deceleration threshold ≈control group Step amplitude = 2 degv = 10 deg/s

  18. R.W.  DotsMean of the Control (n=6): two curves Final acceleration v Final target velocity (deg/s) Final deceleration v Starting target velocity (deg/s)

  19. Unimpaired analysis of object-induced retinal image motion for perceptual and oculomotor purpose • Generally unimpaired on motion analysis during ego-motion. • When a signal encoding the eye movement is not required, performance is normal. (Detection of velocity steps) • Interprets retinal image slips as object motion. Summary

  20. A Deficit in either appropriate reference signalor the internal comparison & very likely located in parieto-occipital lobe (homologous to monkey MST) • The precise localization of human MST  debate. • This area (ignoring background motion) must lie adjacent to V5 (close to ascending limb of the inferior temporal sulcus) • R.W. has lesion in this area (including MST? & V5) • But normal analysis of retinal image motion  a normal V5 ?  Early acquired lesion, brain plasticity kicked in Conclusion & Discussion

  21. Question: The experimenters used a 2D background to test Filehne illusion, but what about the 3D background in real life? • Recalling Counter Strike, the objects in different depth have different speed on retina, how to take this into account? • OK, relax, I will show you something fascinatingSufi whirlingKorean folk dance Last slide, Question and Sufi

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