Neuropsychological Evidence for Category Structure Then: The Functional Role of Mental Imagery Psychology 355: Cognitive Psychology Instructor: John Miyamoto 05/20 /2015: Lecture 08-3 This Powerpoint presentation may contain macros that were used to create the slides. The macros aren’t needed to view the slides. If necessary, you can disable the macros without any change to the presentation.

Outline Finish discussion of semantic networks and spreading activation. Neuropsychological evidence for category representations. Mental Imagery Imagery Debate – Do mental images play a functional role in human cognition? Evidence in favor of the functional role of imagery. Are perception and imagery similar processes? ♦ Behavioral evidence ♦ Neuropsychological evidence Psych 355, Miyamoto, Spr '15 2 Lecture probably ends here Semantic Networks and Connectionist Models

Semantic Networks & Connectionist Models Semantic networks & connectionist models – two different approaches to modeling concept structure. ♦ Semantic networks & connectionist models use different formalisms. Spreading activation – activation of some concepts causes activation in associated concepts. Connectionist models focus on learning concept structure. [This topic will be omitted from Psych 355 this quarter.] Semantic networks focus on modeling human concept structure without modeling how we learn this structure. These are just two of many approaches to the math modeling of concept learning and structure. Psych 355, Miyamoto, Spr '15 3 Semantic Network Models

Concepts are arranged in networks that represent the way concepts are organized in the mind. Psych 355, Miyamoto, Spr '15 4

Example of a Semantic Network Collins and Quillian (1969) Model for how concepts and properties are associated in the mind Node = category/concept Concepts are linked Cognitive economy: shared properties are only stored at higher-level nodes Exceptions are stored at lower nodes Inheritance ♦ Lower-level items share properties of higher-level items Psych 355, Miyamoto, Spr '15 5 Goldstein Figure 9.12

Using a Semantic Network to Predict Sentence Verification Collins & Quillian (1969) Measure response time to verify whether sentence is TRUE or FALSE ("sentence verification" or "semantic memory") Theoretical claim of spreading activation theory: ♦ Activation is the arousal level of a node ♦ When a node is activated, activity spreads out along all connected links ♦ Concepts that receive activation are primed and more easily accessed from memory Psych 355, Miyamoto, Spr '15 6 Goldstein Figure 9.13 (top) & 9.14 (bottom)

Problems with Semantic Networks Distance between nodes does not always predict response time patterns. Example: A canary is a bird. An ostrich is a bird. Example: A pig is a mammal. (RT = ms) A pig is an animal. (RT = ms) Psychologists are searching for a representation of concepts that predicts behavioral results, but no representation is extremely successful. Psych 355, Miyamoto, Spr '15 7 Should be equally fast because network distance is the same, but first sentence faster than second. 1st sentence should faster than 2nd sentence because network distance is shorter, but opposite is true.

Summary re Categorization Categories are not represented by means of definitions. Categories are represented by means of prototypes or exemplars. There is a basic level of categorization. Cognitive psychologists are searching for a computational model of the representation of category information, and the processing of category information. Re semantic networks, spreading activation & connectionist models, what do we need to know for the tests? ♦ Connectionist models - essentially nothing (they exist; they are complicated) ♦ Semantic networks & spreading activation attempt to explain pattern of mental associations. They are fairly successful at predicting sentence verification and priming studies, but are not completely successful. ♦ These are just two of many theories of category structure. Psych 355, Miyamoto, Spr '15 8 Question: What Are Neural Representations of Category Knowledge?

Psych 355, Miyamoto, Spr '15 9 What Is the Neural Representation of Category Knowledge? Are there object-specific or person-specific neural representations? ♦ A related but non-equivalent question: Are there specific neurons that are sensitive to specific objects or persons? Are there grandmother cells? How is knowledge of categories of objects represented at the neural level? Category Specific Neurons

Psych 355, Miyamoto, Spr '15 10 Evidence for Category-Specific Neurons Kreiman, G., Koch, C., & Fried, I. (2000). ○ Single-cell recordings from 11 epilepsy patients awaiting surgery. ♦ Neurons found in the temporal lobe that respond best to specific classes of objects. Category-specific neurons for: ♦ faces; ♦ famous faces; ♦ animals; ♦ cars; ♦ buildings; ♦ spatial layouts; ♦ abstract patterns Grandmother cells ??? Neuropsychological Evidence for Category-Specific Impairments

Neuropsychological Evidence for Category Specific Impairments Double dissociation between ability to name ANIMATE and INANIMATE objects. Sensory-Functional (S-F) Hypothesis: ♦ ANIMATE objects: Identification depends on sensory/perceptual characteristics ♦ INANIMATE objects: Identification depends on function. Psych 355, Miyamoto, Spr '15 11 Source: Mahon, B. Z., & Caramazza, A. (2009). Concepts and categories: A cognitive neuropsychological perspective. Annual Review of Psychology, 60, 27–51. The left panel is identical to Goldstein's Figure Living Animate Same Slide with Explanation of Grey Bars

Neuropsychological Evidence for Category Specific Impairments Psych 355, Miyamoto, Spr '15 12 Source: Mahon, B. Z., & Caramazza, A. (2009). Concepts and categories: A cognitive neuropsychological perspective. Annual Review of Psychology, 60, 27–51. The left panel is identical to Goldstein's Figure Non-Animal (fruit/vegetable + non-living) Double dissociation between ability to name ANIMATE and INANIMATE objects. Sensory-Functional (S-F) Hypothesis: ♦ ANIMATE objects: Identification depends on sensory/perceptual characteristics ♦ INANIMATE objects: Identification depends on function. Same Slide with Explanation of Blue Bars

Neuropsychological Evidence for Category Specific Impairments Psych 355, Miyamoto, Spr '15 13 Source: Mahon, B. Z., & Caramazza, A. (2009). Concepts and categories: A cognitive neuropsychological perspective. Annual Review of Psychology, 60, 27–51. The left panel is identical to Goldstein's Figure Non-Living Double dissociation between ability to name ANIMATE and INANIMATE objects. Sensory-Functional (S-F) Hypothesis: ♦ ANIMATE objects: Identification depends on sensory/perceptual characteristics ♦ INANIMATE objects: Identification depends on function. Multimodal Category Representations

Psych 355, Miyamoto, Spr '15 14 Multimodal Category Representations Category knowledge includes knowledge of.... ♦ an object's visual appearance, e.g., what a dog looks like; ♦ typical sounds, e.g., what kinds of sounds you would expect from a dog; ♦ function, e.g., what you would use a hammer for; ♦ smell, e.g., what a dog smells like; what a flower smells like; what a fire smells like; ♦ taste, especially true of foods ♦ typical body actions that relate to it, e.g., we have a representation of the body actions with respect to a hammer, a chair, a chest of drawers Multimodal representations involve multiple sensory modes, vision, audition, touch, kinesthesis, and so forth. Example: The Grasping Circuit

Example of a Multimodal Category Representation: The Grasping Circuit for Manipulable Objects The Grasping Circuit – a neural circuit associated with use of manipulable objects, like hammers, screwdrivers, tennis rackets, etc. ♦ Involves pathways in parietal cortex Question: Are the neural circuits involved in handling a hammer part of the category representation of "hammer"? Psych 355, Miyamoto, Spr '15 15 fMRI Images While Viewing Hammers, Buildings, Animals & People,

Neural Evidence for Multimodal Representations of Category Knowledge Hammer use activates the left ventral premotor cortex & left posterior parietal cortex (grasping circuit). Subjects are immobile in the scanner so they could not grasp anything. Nevertheless, viewing a hammer activated the grasping circuit. ♦ Supports the hypothesis that we activate object-appropriate motor association areas when we access category knowledge. ♦ Supports the view that category knowledge is multimodal. ♦ This is an example of semantic somatotopy - perceiving object activates brain areas associated with body actions relating to the object. Psych 355, Miyamoto, Spr '15 16 Summary: Neural Representations of Category Knowledge

Psych 355, Miyamoto, Spr '15 17 Summary – Neural Representations of Category Knowledge Some neurons may be specific to particular people or objects. (Grandmother cells - controversial issue) Some neural mechanisms are specific to particular kinds of objects. ♦ Not necessarily single neurons – the mechanism may involve distributed processing. Neural category representations are multimodal. As yet, we only have a preliminary understanding of neural representations of category knowledge. This is a good field for someone with a scientific pioneering spirit. Visual Images - What Are They?

Psych 355, Miyamoto, Spr '15 18 Wednesday, May 20, 2015 : The Lecture Ended Here