08b vision processing form and shape short


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08b vision processing form and shape short

  1. 1. Visual Signal Processing Hubel Wiesel
  2. 2. Neuronal architecture of mammalian visual system
  3. 3. Retina Functional organization
  4. 4. Anatomical Distribution of Rods and Cones
  5. 5. Phototransduction
  6. 6. Receptive Field Receptive fields of photoreceptors and their connections. (A) The receptive field center provides a direct input from the photoreceptors to the bipolar cell, and the receptive field surround provides indirect input from the photoreceptor to the bipolar cells via horizontal cells. (B) 1: Photoreceptor cell; 2: on-center bipolar cell; 3: off-center bipolar cell; 4: on-center ganglion cell; 5: off-center ganglion cell.
  7. 7. Receptive field of Retina
  8. 8. Ganglion Cell : Contrast discrimination
  9. 9. Receptive field of bipolar and ganglion cells
  10. 10. Ganglion Cells Characteristics M Cells P Cells Color No Yes Contrast High Low Spatial Low High Temporal High Low Population 5% 90% Action Potential Phasic, fast Tonic, slow Function Movement Shape Receptive field Large Small Retinal mapping Periphery Fovea
  11. 12. Central Projections of Retinal Ganglion Cells
  12. 13. Lateral Geniculate Ganglia
  13. 14. Retinal projection to Lateral Geniculate Nucleus
  14. 15. Central retinal pathway
  15. 16. LGN Projection to Occipital Cortex
  16. 17. Primary Visual Cortex information flow
  17. 18. The Primary Visual Cortex
  18. 19. The ocular dominance columns
  19. 21. Ocular Dominance Column input from LGN R L
  20. 22. The overlap and blurring of ocular-dominance columns beyond layer 4 is due to horizontal or diagonal connections.
  21. 23. Orientation column of visual cortex: Optical imaging
  22. 24. Organization of Blobs in visual cortex
  23. 25. Primary Visual Cortex Architecture
  24. 26. Receptive field of a simple cell in the primary visual cortex
  25. 27. Simple cell of visual cortex
  26. 28. Complex Cell
  27. 29. What Primary Visual Cortex do?
  28. 30. Projection of LGN to V1 <ul><li>A, sends a signal to many simple cells, each with different orientations. In this figure, cell A shares its information with 3 simple cells. If there were a simple cell for each 5 deg change in orientation, the same cell A would provide information to 36 simple cells (180 deg/ 5 deg = 36). </li></ul>
  29. 31. Complex Cells
  30. 32. Retinal image of an object
  31. 33. Significance of Movement Cells
  32. 34. A rough indication of physiological cell types found in the different layers of the striate cortex.
  33. 35. Hypercomplex Cells End Stopping cells
  34. 36. V2-3: Assembling simple features into objects. V1 V2
  35. 37. Binding Problem
  36. 38. Binding Problem
  37. 39. Illusory contour
  38. 40. What we perceive depends not only on the visual image but also on our interpretation of what we see Interpretation based on our memories modifies what we see. For example if we expect to see the letter m in “exanple” we may not notice that is has been misspelled.
  39. 41. <ul><li>AIT = anterior inferior temporal area; CIT = central inferior temporal area; LIP = lateral intraparietal area; Magno = magnocellular layers of the lateral geniculate nucleus; MST = medial superior temporal area; MT = middle temporal area; Parvo = parvocellular layers of the lateral geniculate nucleus; PIT = posterior inferior temporal area; VIP = ventral intraparietal area.) (Based on Merigan and Maunsell 1993.) </li></ul>
  40. 42. Inferior Temporal neuron response to Form
  41. 43. Face and Complex Form Recognition ITC
  42. 44. Fusiform face area
  43. 45. Columnar organization of IT area <ul><li>IT has a columnar organization Cells within a column are activated by the same object. Neighboring columns respond best to objects of a similar shape as in a and b. </li></ul>