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Visual perception

Visual perception. Stuart red. Any difference in the pictures?. What if they are right side up?. Sereno Lab Approaches to Cognitive Neuroscience. Behavioral Testing Eye Movements Touch Responses Monkey Physiology Computational Modeling Integration of All Approaches. Visual system.

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Visual perception

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  1. Visual perception Stuart red

  2. Any difference in the pictures?

  3. What if they are right side up?

  4. Sereno Lab Approaches to Cognitive Neuroscience • Behavioral Testing • Eye Movements • Touch Responses • Monkey Physiology • Computational Modeling • Integration of All Approaches

  5. Visual system

  6. The visual system is complicated

  7. Different streams

  8. What and where pathways

  9. A little bit of history

  10. Parietal lesions created difficulty with localizing objects “… vision was evidently defective… it was able to pick up grains of rice scattered on the floor, but always with uncertainty as to their exact position.”

  11. Early view of parietal lesions in humans • Sir Gordon Holmes (1918) described bilateral posterior parietal lesion patients with deficits in: • reaching and pointing to visual targets • Avoiding obstacles • Judging distance and size • No issues in object recognition • W.R. Brain (1941) • Unilateral lesions • Contralateral neglect

  12. A little bit of history

  13. Inability to discriminate between objects “He appears no longer to discriminate between the different kinds of food ; e.g., he no longer picks out the currants from a dish of food…”

  14. Kluver-bucy syndrome • Thought hallucinations preceding temporal lobe seizures were similar to mescaline induced hallucinations • Removed temporal lobes from monkeys and administered mescaline • No difference in effects of mescaline but… • When off the drug, these monkeys exhibited “psychic blindness” or “visual agnosia” • Along with a host of other symptoms…

  15. Ungerleider and mishkin 1982

  16. Ungerleider and mishkin 1982

  17. results

  18. Stare at the center of the screen

  19. Akinetopsia

  20. Functional Specialization- Ventral Complex stimuli: star shape shape & texture JJ, Fig 2.3 (Tanaka, 1991)

  21. Functional Specialization- Ventral Complex stimuli: hand orientation, not important position, not important bilateral, near fovea best Fig 6.6

  22. Why are eye movements so important?

  23. Cones densely packed at fovea

  24. History of eye tracking • Edmund Huey (1898) • Used plaster of paris cup molded to fit the cornea with whole for subject to read through

  25. Alfred Yarbus (1950s and 1960s)

  26. Modern eye tracking

  27. What can we learn about attention through eye movements?

  28. Attention • Attention filters out irrelevant information • Reflexive vs voluntary attention • Reflexive attention involves the more automatic response • Voluntary attention involves more thought

  29. Reflexive vs Voluntary

  30. Reflexive vs Voluntary

  31. Reflexive vs Voluntary

  32. Reflexive vs Voluntary

  33. Prosaccade and antisaccade task

  34. What’s required for antisaccade? • Subject must inhibit the reflexive response and transform the stimulus location into a voluntary movement to look away • Requires inhibition of saccade producing neurons in SC and FEF • Where this inhibition is coming from remains a question, could be Basal Ganglia, SEF, or DLPFC

  35. Error rate is much larger for antisaccade

  36. Prosaccade & Antisaccade RT

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