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The visual pathways

The visual pathways. 0. 1. Ventral pathway receptive field properties. TE receptive field. V1 receptive field. V4 receptive field. “What” and “Where” visual streams. From: Mishkin, Ungerleider & Macko (1983). Functional organization of the visual system

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The visual pathways

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  1. The visual pathways

  2. 0 1 Ventral pathway receptive field properties TE receptive field V1 receptive field V4 receptive field

  3. “What” and “Where” visual streams From: Mishkin, Ungerleider & Macko (1983)

  4. Functional organization of the visual system Segregation of form, color, movement, and depth. Livingstone & Hubel, 1988

  5. Magno and parvo pathways Origin of visual pathways: The LGN

  6. Contributions of M and P pathways to vision Experimental Conditions Where is the target stimulus? Which stimulus is the “odd one out”? Discrimination Detection Schiller & Logothetis, 1990

  7. Shape perception is impaired at isoluminance

  8. Function Tested Result of “P” Lesion Result of “M” Lesion Color vision Deficit Normal Texture Perception Deficit Normal Pattern Perception Deficit Normal Acuity Deficit Normal Contrast Perception Deficit Normal Flicker Perception Normal Deficit Major Behavioral Results of “M” and “P” Lesions in the LGN

  9. The monkey & human cortex

  10. Hierarchy of visual processing stages

  11. Vision for action Object recognition Goodale & Milner 1992

  12. Objects> scrambled objects James et al., 2003 Goodale & milner’s Subject DF

  13. A set of 12 asymmetric shapes • Same set was used for: • same/different discrimination. • Grasping movements

  14. Comparing RV and DFin the same/different task

  15. Points of 2-finger grasping

  16. MRI vs. fMRI MRI fMRI high resolution (1 mm) low resolution (3 mm) one image • fMRI • Blood Oxygenation Level Dependent (BOLD) signal • indirect measure of neural activity …  neural activity   blood oxygen   fMRI signal Source: Jody Culham’s fMRI for Dummies web site

  17. Physiological basis of fMRI

  18. ROI Time Course fMRI Signal (% change) ~12s Condition Time Condition 1 Statistical Map superimposed on anatomical MRI image Condition 2 ... Region of interest (ROI) ~ 9 min Activation Statistics Functional images Time Source: Jody Culham’s fMRI for Dummies web site

  19. A Look at D.F.’s brain Objects> scrambled objects

  20. An event related fMRI of DF’s grasping

  21. The Ebbinghaus illusion

  22. Dissociation of perception and action in the Ebbinghaus illusion

  23. Shmuelof & Zohary, Neuron 2005

  24. fMRI study: Viewing object manipulation clips • Signa Horizon 1.5T GE scanner. • Gradient-echo EPI sequence (TR = 3000, TE = 55, flip angle = 90°, FOV: 24´24 cm2 ). • 27 nearly-axial slices of 4mm thickness and 1mm gap. • T1-weighted high resolution (111mm) anatomical images

  25. Experiment 1 – laterality effect Task Object "Name the object” Action “how many fingers touch the object?”

  26. Action vs. Object representation >

  27. * ** % signal change sec aIPS FuG * FuG Regions Of Interest analysis > n=11 Left hemisphere Right hemisphere aIPS

  28. two jar Task-related activation < Object-oriented task Action-oriented task n=11

  29. time Experiment 2 – Object vs. Grasp adaptation effect

  30. Object-based Vs. Grasping-based Adaptation

  31. Regions Of Interest analysis aIPS % signal change • Object-based adaptation • in ventral ROIs. • Grasping-based adaptation • in dorsal ROIs. FuG So So Do Do Dg Sg Sg Dg

  32. Milner and Goodale’s conceptual novelty • The division between these streams is task rather than stimulus based. • Rather than a division of stimulus attributes – the division relates to “how it’s going to be used”

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