Ventral stream

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Object recognition and the ventral "what stream". Used for a university course on visual perception.

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  • Other studies also show changes between LO and FFA for the Rubin face-vase illusion
  • Ventral stream

    1. 1. What are you looking at? Mechanisms of visual recognition.Barbara NordhjemVisual Neuroscience GroupLaboratory of Experimental OphthalmologyUniversity Medical Center Groningen
    2. 2. Human recognition • Gist of the scene at 7 images per second. • Unpredictable random QuickTime™ and a Sorenson Video 3 decompressor sequence of images are needed to see this picture.Potter 1971, 1975; Biederman 1972; Thorpe 1996 Movie by Jim DiCarlo
    3. 3. • Images change: object position, distance, pose, lighting and background clutter. Yet we know where to attend and what we are looking at.
    4. 4. Moving beyond V1• What happens at the cellular level after V1?
    5. 5. Simple Cells Hubel & Wiesel, 1959, 1962, 1965,1968
    6. 6. Gradual more complex preferred stimulus Tanaka, 1996
    7. 7. Parallel increase in invariance properties (position and scale)of neurons Illustration from Rousselet et al., 2004
    8. 8. Pathways in the brain• Lesions parietal lobe (Newcombe, 1969)• Ungerleider and Mishkin (1982) lesions in monkeys. Suggested regions organized in pathways• Goodale and Milner (1992) distinguish between perception and action Figure by Mike Cohen
    9. 9. • The case of DF: visual form agnosia • Carbon monoxide poisoning • Lesion of lateral occipital cortex
    10. 10. Goodale et al., 1991
    11. 11. Aglioti et al., 1995
    12. 12. Are people attending to bothconstellations when they grasp?Patient (AT) with parietal lesions wasbetter grasping familiar than novelobjects – interaction of memory andaction control (Jeannerod et al.,1994). Aglioti et al., 1995
    13. 13. Modules in the brainProcessing areas withthe ventral pathway:Faces, Objects, Places Figure by Mike Cohen
    14. 14. Face and form agnosiaSome patients show a specific deficit for recognizing faces, others showdeficits for recognizing all other objects.Faces and objects are processed in separate, perhaps non-overlapping,brain areas.
    15. 15. The idea of functionally specialized regions
    16. 16. Lateral Occipital (LO)Malach, Levy, & Hasson, 2002 Grill-Spector et al., 1998
    17. 17. Levels of recognitionGauthier et al., 1999, 2000
    18. 18. Visual awareness
    19. 19. Right FFAAndrews et al., 2002
    20. 20. Two types of bistable figures One-category Two-category
    21. 21. One-category > Two-categories
    22. 22. Different ways of seeing
    23. 23. Peripheral and central vision Levy et al., 2001
    24. 24. Form and texture Cant & Goodale, 2007
    25. 25. Cant & Goodale, 2007
    26. 26. Representation in ventral areasFreeman& Simoncelli, 2011
    27. 27. Fast saccade bias towardsfaces, event for phasescrambled imagesHoney et al, 2008Spatial scales: coarse and finerepresentation Olivia, 2007
    28. 28. More than one ventral pathway?
    29. 29. Summary• Parallel increase in invariance to position and scale of neurons from V1 to IT• Specialized information processing• Dorsal and ventral pathways for action and perception• Keep in mind that the idea of pathways and specialized regions is simplified visualneuroscience.nl

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