Motion deficits

1. Motion deficits

2. Introduction • Previous two motion lectures reported psychophysics and physiology involving intact brains • We can learn about motion processing by damaging parts of the motion processing system and seeing how that affects performance • Two approaches: • Lesion studies in animals • Patients with brain damage

3. Superior temporal gyrus Superior temporal sulcus (STS) (Image from Barraclough & Perrett, 2011) MT V4 V2 V1 Lesion studies in macaque monkey: MT

4. Newsome & Paré (1988) – Motion task • Trained monkeys to discriminate direction of motion coherence stimulus • Coherently moving dots are the “signal” • Randomly moving dots are the “noise” • Each dot has a short lifetime • Stimulus stimulates motion mechanisms without having easily trackable features • Vary proportion of dots moving in coherent direction until the monkey can only just do the task

5. Newsome & Paré (1988) – Motion task • Fixate on FP1 or FP2 during stimulus presentation • Move gaze to upper point if upward motion perceived • Move gaze to upper point if downward motion perceived • Adjusted proportion of coherently moving dots until performance was at threshold

6. Newsome & Paré (1988) – Control task • Fixate on FP during stimulus presentation • Move gaze to upper point if target vertical • Move gaze to opposite side if target horizontal • Adjusted contrast of grating until performance was at threshold

7. “Speed”, i.e. visual angle jumped between frames (45 ms apart) Newsome & Paré (1988) – Motion task • After training and data collection, lesioned MT on one side of brain with injections of ibotenic acid, and assessed task performance 24 hrs later • MT on each side of brain only responds to contralateral visual hemifield

8. Newsome & Paré (1988) – Control task • After training and data collection, lesioned MT on one side of brain with injections of ibotenic acid, and assessed task performance 24 hrs later • MT on each side of brain only responds to contralateral visual hemifield • MT lesion selectively impairs motion perception on contralateral side

9. Newsome & Paré (1988) – Recovery • After 24 hours, performance very bad • After 9 days, performance back to pre-lesion level • Electrophysiological recordings indicated lesion didn’t destroy all of MT • So they injected more ibotenic acid

10. Newsome & Paré (1988) – Recovery • After 24 hours, performance very bad again • After 3 weeks, performance nearly back to pre-lesion level, but not quite • Conclusion: MT heavily involved in motion processing, but other brain regions can learn to support performance on this task

11. Superior temporal gyrus MT/V5 in normal subjects (from Watson et al, 1993) Humans Superior temporal sulcus (STS) Macaque monkey brain MT Human brain

12. Motion blindness (akinetopsia) in humans • Pötzl & Redlich (1911) • Bilateral occipital injury • Moving objects appeared at different successive positions • Normal color and form vision • Severe visual field restriction (could only see small part of visual field) • So the apparently selective motion impairment could have been caused by stimulus moving out of the spared portion of visual field • Goldstein & Gelb (1918): patient “Schn.” • Brain injury sustained during World War I • Motion impairment accompanied by alexia, form agnosia, loss of visual imagery, tactile agnosia, loss ofbody schema, loss of position sense, acalculia and loss ofabstract reasoning • Many have suspected the patient of exaggerating his symptoms • “did not spontaneously complain of any visual deficiencies... performed well at visually exacting work...However, he did display striking ab-normalities when visual functions were examined” (Goldenberg, 2003)

13. Zihl, von Cramon & Mai (1983) • The case of LM • 43-year old German woman with acquired motion blindness • Brain damage due to thrombosis • Fatigued easily, but in normal ranges on all cognitive measures • Unable to see motion - things appeared to change position suddenly • Avoided crowded places because “people were suddenly here or there but I have not seen them moving”

14. Zihl, von Cramon & Mai (1983) • The case of LM • 43-year old German woman with acquired motion blindness • Brain damage due to thrombosis • Fatigued easily, but in normal ranges on all cognitive measures • Unable to see motion - things appeared to change position suddenly • Avoided crowded places because “people were suddenly here or there but I have not seen them moving” • Difficulty pouring tea into a cup because the fluid appeared to be “frozen, like a glacier.” • Difficulty crossing streets: “When I'm looking at the car first, it seems far away. But then, when I want to cross the road, suddenly the car is very near”

15. LM – Location of brain damage • Lesion similar on each side of brain • Mainly destroyed MT/V5 (Shipp, de Jong, Zihl, Frackowiak & Zeki, 1994)

16. Foveal horizontally moving dot Foveal vertically moving dot LM – Motion perception (Zihl et al, 1983) • In fovea, she could see slow motion, but not fast motion

17. LM – Motion perception (Zihl et al, 1983) • Peripheral motion - near chance when discriminating motion direction in periphery

18. Then disappears ... LM – Motion prediction (Zihl et al, 1983) • Subject presses button at the moment when square would have got to the bar White square moves ... • Normal control performs veridically • LM was OK for slow speeds, but greatly underestimated fast speeds.

19. LM – Motion aftereffect (Zihl et al, 1983) “unrest” on 3/10 trials no aftereffect

20. LM – Phi motion (Zihl et al, 1983) LM reported two spots blinking on and off

21. Auditory motion • Easily discriminated direction and accurately pointed at moving sound source. LM – Non-visual motion (Zihl et al, 1983) • Tactile motion • “the upper side of the patient’s right forearm was stimulated with a small wooden stick” • task = “which direction is this moving in?” • 100% correct • So not a general problem of motion perception

22. Foveal colour vision – normal Visual acuity – normal Stereopsis – normal LM – non-motion vision

23. Visually evoked potentials – normal LM – non-motion vision (Zihl et al, 1983) DONKEY Word and object recognition time – normal

24. red green blue Maximum eccentricity for detection of different coloured lights – normal LM – visual fields normal (Zihl et al, 1983) Maximum eccentricity for detection of white lights of different luminance – normal 0.3 cd/m2 3.2 cd/m2 320 cd/m2

25. Normal form field (maximum eccentricity for discrimination between circles and diamonds of different sizes) Normal critical flicker fusion (CFF) fields (maximum eccentricity for detection of flicker at different rates (20, 30 and 35 Hz) LM – visual fields normal (Zihl et al, 1983) • Interesting that CFF fields are normal – one might expect flicker detection to be related to motion perception • In summary, apparently selective impairment of visual motion processing

26. Zihl, von Cramon & Mai (1983) • Conclusions based on initial assessment • Appeared to be selective impairment of visual motion processing • Within central 15 deg vis angle, somewhat preserved motion impression, detection and discrimination for <10deg/s; Near-absent motion perception in periphery • Not a deficit in temporal acuity (flicker fusion thresholds normal) • Motion perception in other modalities spared • Other visual functions appeared normal

27. Contrast sensitivity for stationary sine-wave gratings Hess, Baker & Zihl (1989) • Better quality psychophysics (2-alternative forced-choice) • But still only one control subject on each task

28. Hess, Baker & Zihl (1989) Contrast sensitivity for flickering sine-wave gratings

29. Hess, Baker & Zihl (1989) Contrast sensitivity for drifting sine-wave gratings • In summary, contrast sensitivity around 2-3 times below normal • LM needed contrast to be about 2-3 times higher than controls to match control performance

30. Hess, Baker & Zihl (1989) Contrast discrimination for stationary sine-wave gratings • One stimulus (the pedestal) has contrast c, the other has contrast c + c • Subject has to pick the higher contrast • Plot % correct as a function of c • LM required c to be about 3 times bigger than controls

31. Hess, Baker & Zihl (1989) Spatial frequency discrimination for stationary sine-wave gratings • One stimulus (the base) has spatial frequency f, the other is f + f • Subject has to indicate which is which • Plot % correct as a function of f (expressed as percentage of f) • LM required f to be about 5 times bigger than controls

32. Hess, Baker & Zihl (1989) Temporal frequency discrimination for stationary flickering gratings • One stimulus (the base) has temporal frequency f, the other is f + f • Subject has to indicate which is which • Plot % correct as a function of f (expressed as percentage of f) • LM required f to be about 10 times bigger than controls

33. Hess, Baker & Zihl (1989) Speed discrimination for drifting sine wave gratings • One stimulus (the base) has temporal frequency f, the other is f + f • Subject has to indicate which is which • Plot % correct as a function of f (expressed as percentage of f) • LM required f to be about 20 times bigger than controls

34. LM more severly impaired discrimination tasks: Threshold was ... • 3 times higher than normal for contrast discrimination • 5 times higher than normal for spatial frequency discrimination • 10 times higher than normal for temporal frequency discrimination • 20 times higher than normal for speed discrimination Hess, Baker & Zihl (1989) – Summary • LM mildly impaired on contrast sensitivity (normal subjects about twice as sensitive) • Contrast sensitivity is measured using detection tasks, which can be mediated by looking at a single mechanism • Discrimination tasks require comparison of output of two mechanisms • Maybe LM has “a general disability for tasks that critically depend on cross-filter comparisons” (Hess et al, 1989, p. 1630) • This would impair motion perception because motion processing involves comparison of outputs of mechanisms tuned to opposite directions (motion opponency)

35. Baker, Hess & Zihl (1991) Used same motion coherence task as Newsome & paré (1988)

36. Baker, Hess & Zihl (1991) Used same motion coherence task as Newsome & paré (1988)

37. Baker, Hess & Zihl (1991) Motion discrimination performance as a function of coherence level • LM can discriminate motion direction quite reliably when coherence level is 100% • Tiny proportion of noise dots obliterates performance

38. Baker, Hess & Zihl (1991) Motion discrimination performance as a function of coherence level • LM can discriminate motion direction quite reliably when coherence level is 100% • Tiny proportion of noise dots obliterates performance • Performance very bad even when the noise dots are stationary with unlimited lifetime • Does performance get worse because of the presence of the noise or because of lower number of signal dots? • Made the noise dots invisible

39. Baker, Hess & Zihl (1991) Motion discrimination performance as a function of coherence level • LM can discriminate motion direction quite reliably when coherence level is 100% • Tiny proportion of noise dots obliterates performance • Performance very bad even when the noise dots are stationary with unlimited lifetime • Does performance get worse because of the presence of the noise or because of lower number of signal dots? • Made the noise dots invisible • Performance improved dramatically • Baker et al. proposed that LM has general difficulty dealing with noise

40. Rizzo, Nawrot & Zihl (1995)– Motion tasks Identify letter defined by motion of dots within figure, against stationary background texture • LM highly impaired Identify letter defined by motion of dots within figure, without background texture • LM mildly impaired Identify letter defined by absence of dots within figure, against coherently moving background texture • LM performed very well (close to ceiling)

41. Rizzo, Nawrot & Zihl (1995)– Static tasks Identify letter defined by texture orientation difference between figure and background • LM close to chance Identify letter defined by use of different texture elements in figure and background • LM highly impaired Identify letter defined by dot density • LM mildly impaired

42. Three Surprising Things 1) Although complete MT lesions initially obliterated performance on motion coherence task in monkeys, performance recovered over a few weeks almost to pre-lesion levels • Brain areas other than MT can learn to support the motion coherence task 2) Although patient LM initially appeared to have highly selective impairment of motion perception, further testing suggested that she had more general problems, which were not specific to motion: • She had difficulty separating signal from noise both for moving and static visual stimuli • She had difficulty comparing the outputs of different mechanisms, leading to poor discrimination performance even with static stimuli 3) Despite the wealth of evidence against it, Josef Zihl still pushes the view that LM’s case provides “compelling evidence for a selective and specific loss of movement vision” (Zihl & Heywood, 2015)

43. 1st-order vs 2nd-order motion 1st-order motion 2nd-order motion • Vaina & Cowey (1996) reported patient FD, with lesion to MT, who was selectively impaired at tasks involving 2nd-order motion, but OK at tasks involving 1st-order motion • Vaina, Soloviev, Bienfang & Cowey (2000) reported patient TF, with small lesion to V2, who was selectively impaired at tasks involving 1st-order motion, but OK at tasks involving 2nd-order motion

44. Ventral areas contribute to foveal motion • Gilaie-Dotan, Saygin, Lorenzi, Egan, Rees & Behrmann (2013) report a group study of 5 patients with ventral lesions • All had impairments of motion perception in central vision • Suggests MT involved in periphery, but ventral areas involved in motion perception in central vision • May explain LM’s relatively spared motion perception in central vision

45. Further Reading Blake, R., Sekuler, R. & Grossman, E. (2003) Motion processing in human visual cortex. In J.H. Kaas and C.E. Collins (Editors), The Primate Visual System. Boca Raton: CRC Press. This review has a good section on motion-blindness