Spatial representation and coordinate frames in the brain

1. Spatial representation and coordinate frames in the brain

2. Hemispheric Neglect Unilateral Neglect: failure to attend to (or represent) sensory information in the left (contralesional) side of space, following right brain parietal injury.

3. Neglect as a deficit in representation • Bisiach & Luzzati (1978): imagining a familiar scene (e.g., central square of Milan), from opposite view points

4. Parietal lesions in the right hemisphere are commonly associated with left field neglect Yellow: the lesion typically involves the supramarginal gyrus at the temporoparietal junctionRed: variation in the exact extent of the lesionDriver and Mattinagley, NNS, 1998

5. Common tests for Visual Neglect • Drawing from memory

6. copying pictures or words

7. crossing out items

8. line bisection

9. reading words

10. “Burning house”:Implicit processing of the unattended side

11. Neglect can be in egocentric and/or allocentric reference frames

12. Egocentric/allocentric neglect

13. Scene/view/object centered neglect Hillis & Caramazza 1990

14. SEF neurons show selectivity for saccade direction Olson 2003

15. An SEF neuron that shows selectivity on bar-left trials regardless of the saccade’s physical direction

16. Posterior parietal cortex – parietal reach region

17. Eye position gain fieldsin parietal cortex Andersen et al., 1985

18. neurons with head centered RF(in VIP) (Duhamel et al., 1997)

19. Coordinate transformations

20. Neuronal activity in area 5dependence on eye & hand position fixed eye position fixed hand position 1 sec Buneo et al., 2002

21. What’s the coordinate system of these neurons?

22. Target Buttons Initial hand position Initial eye position PRR neuronal activity:Reach Plans in Eye-Centered Coordinates Same eye position Same hand position

23. optimal target position depends on

24. Tactile-visual processing in peripersonal space

25. Peripersonal space-The immediate space surrounding the body (or a certain body part).Extrapersonal space – unreachable.

26. Integrated visual-tactile coding of peripersonal space, centered on body parts Tactile RF Visual RF Iriki A. et al., Neuroreport 1996

27. Response of neuron (spike/sec) Stimulus trajectory Representation of visual information in hand-based coordinates 1 2 3 4 1 2 3 4 Tactile RF Visual stimulus trajectory Graziano MS., PNAS 1999

28. The cell’s response doesn’t depend on fixation position

29. Neurons with multimodal receptive fields were found in areas: -Ventral premotor -Ventral intraparietal (VIP) -Parietal BA 7b, 5 - Putamen

30. Postural bimodal neurons in area 5 respond to the seen position of the hand M.S. Grazianoet al., Science (2000)

31. The effect of the fake arm M.S. Grazianoet al., Science (2000)

32. The rubber hand illusion It’s mine!

33. Pointing at my hand? Botvinick and Cohen, 1998, Nature

34. The rubber hand illusion in the fMRI scanner

35. The rubber hand illusion

36. Brain activity - 2 Linear relationship subjective rating of the illusion vs. level of PM activity R2= 0.3969, P<0.003 R2= 0.3982, P<0.002 * Also found in R. cerebellum.

37. Makin et al 2007