Cogsci/Psychology 127: Lecture 10 Category Specific Perception

1. Cogsci/Psychology 127: Lecture 10 Category Specific Perception

2. First Exam: Next Monday, October 6 FORMAT: Multiple Choice, Short Answer, Essay Essay: Describe experiment w/ graph! Bring small SCANTRON No scheduled make-ups. Notify me (not GSI) early if there is a problem. Review: Last year’s exams are posted. Good study guide. Textbook, Reader guide. Question and Answer Session: TONIGHT!! 5:30 pm. Tolman 5101

3. Subtypes of Visual Agnosia Apperceptive agnosia Failure to organize a coherent percept. What is it?

4. Subtypes of Visual Agnosia Apperceptive agnosia Failure to organize a coherent percept. What is it?

5. Subtypes of Visual Agnosia Apperceptive agnosia Failure to organize a coherent percept. Breakdown of object constancy. Can recognize top picture but not bottom picture.

6. Subtypes of Visual Agnosia Apperceptive agnosia Failure to organize a coherent percept. Breakdown of object constancy. Associative agnosia Failure to access semantic knowledge. Which objects serve same function? A disconnection syndrome.

7. Object recognition requires successful categorization: Different percepts share similar properties. Same thing: identity Same type of object Same class of object Same function. Two types of categorization: Perceptual: Object constancy Apperceptive agnosia Functional: Semantic Associative agnosia

8. Subtypes of Visual Agnosia Apperceptive agnosia Failure to organize a coherent percept. Breakdown of object constancy. Associative agnosia Failure to access semantic knowledge. A disconnection syndrome. Some patients show category specific deficits.

9. Patient JBR shows disproportionate impairment in recognizing living things. 6% correct 90% correct

10. Many reports of similar selective problem recognizing living things. A few reports of patients with greater difficulty recognizing living things, but weak evidence.

11. Many reports of similar selective problem recognizing living things. A few reports of patients with greater difficulty recognizing living things, but weak evidence. Why is deficit with living objects much more common?

12. Describe LEOPARD TOMATO

13. Describe LEOPARD TOMATO IRON HAMMER

14. Multiple Access Hypothesis Representation of living things is primarily visual. Representation of non-living things is visual and functional. Multiple routes to access knowledge. Functional/sensorimotor can support object recognition even if visual access system is noisy due to lesion.

15. Multiple Access Hypothesis Representation of living things is primarily visual. Representation of non-living things is visual and functional. Multiple routes to access knowledge. Functional/sensorimotor can support object recognition even if visual access system is noisy due to lesion. How would you test multiple access hypothesis for recognition of non-living things? Exam Practice

16. Compare activation in sensorimotor regions for living and non-living things that can either be manipulated or not manipulated. Living Non-Living Manipulate NOT Identify Region of Interest (ROI) in premotor cortex. Measure BOLD response when people judge if stimulus is “Manmade” or “Natural”.

17. Compare activation in sensorimotor regions for living and non-living things that can either be manipulated or not manipulated. Living Non-Living Manipulate NOT Premotor Cortex ROI Animals Veggies/Fruits Big Objects Clothing

18. Prosopagnosia Deficit in recognizing faces Category specific deficit Restricted to visual modality

19. Deficit in recognizing faces Category specific deficit Restricted to visual modality Hypotheses to account for disorder Face perception as a difficult discrimination. Faces: Within-category discrimination Objects: Usually between-category discrimination Prosopagnosia

20. The prosopagnosic sheep farmer NOTE: Middle face is famous British Politician of 1980’s

21. Recognition Memory for Faces of Sheep and Famous People (percent correct) Patient WJ Controls (sheep farmers) Familiar Sheep 87% 59% Unfamiliar Sheep 81% 63% Faces 50% 100%

22. Recognition Memory for Faces of Sheep and Famous People (percent correct) Patient WJ Controls (sheep farmers) Familiar Sheep 87% 59% Unfamiliar Sheep 81% 63% Faces 50% 100% NOTE: WJ better than Controls at sheep recognition.

23. Deficit in recognizing faces Category specific deficit Restricted to visual modality Hypotheses to account for disorder Face perception as a difficult discrimination. Specialized processing system for faces. Evolutionary motivation. Prosopagnosia

24. Deficit in recognizing faces Category specific deficit Restricted to visual modality Hypotheses to account for disorder Face perception as a difficult discrimination. Specialized processing system for faces. Evolutionary motivation. Single-cell recordings in temporal lobe Prosopagnosia

25. Single cell recordings in monkey temporal lobe

26. Prosopagnosia Deficit in recognizing faces Category specific deficit Restricted to visual modality Hypotheses to account for disorder Face perception as a difficult discrimination. Specialized processing system for faces. Evolutionary motivation. Single-cell recordings in temporal lobe fMRI: Fusiform Face Area (FFA) (medial, inferior temporal lobe)

27. FFA FFA consistently identified in fMRI studies in all sorts of comparisons. R L R L

28. Are faces just stronger stimuli, perhaps because of biological relevance? Perhaps faces and objects engage identical regions but our brains are more sensitive to faces. Single dissociation problem.

29. Are faces just stronger stimuli, perhaps because of biological relevance? No. Double dissociation between faces and places. FFA: Fusiform face area PPA: Parahippocampal place area Note activation (weaker) during imagery.

30. Biological questions: What stimulus features lead to FFA activation? Sensitive to face-like stimuli, human or otherwise. Sensitive to face parts, even without full face.

31. Biological questions: Is FFA only activated by faces? No Grey lines are all stimuli. Light lines are remembered stimuli.

32. Biological questions: Is face-sensitive region causally involved in face perception? Monkey makes eye movement to indicate if stimulus is flower or face. Microstimulation in face-sensitive cells in inferior temporal cortex. Does stimulation influence their “judgment”?

33. Biological questions: Is face-sensitive region causally involved in face perception? Probability of responding “face” increases with stimulation.

34. Cognitive question: Why is face perception special?

35. Cognitive question: Why is face perception special? Most object perception involves an analytic process. Identify parts to construct the whole. Face perception primarily based on holistic or configural analysis.

36. Farah’s process model: Accounts for patterns of association and dissociation.

37. Agnosia Patient CK clueless at identifying objects But no problem in recognizing “face”.

38. CK as a pure holistic perceiver. Recognizes overall shape with severe impairment in recognizing parts.

39. Are faces special? Yes. Among our visual skills, face recognition seems especially dependent on holistic analysis. Object perception dominated by parts analysis. With expertise, increased activation in fusiform region for non-facial stimuli (flowers, butterflies, cars). But activation foci may be outside face regions within fusiform area that responds to faces (FFA). Expertise associated with increased holistic processing.