WHAT, WHERE, & HOW SYSTEMS AGNOSIAS!

1. WHAT, WHERE, & HOW SYSTEMSAGNOSIAS!

2. What, Where, & How Systems

3. What

4. Visual Agnosia

5. Visual Object Agnosia • Apperceptive • Associative

6. Apperceptive Agnosia • Intact vision: • Acuity, brightness discrimination, color vision, & other elementary visual capabilities • Sometimes preserved shape from motion • Deficits: • Abnormal shape perception (pictures, letters, simple shapes) • Grouping process deficit (that operates over an array of local features representing contour, color, depth, etc.)

7. Apperceptive Agnosia • VIDEO: Apperceptive Agnosia, impaired triangle recognition, subject 1 • VIDEO: Apperceptive Agnosia, impaired object recognition, subject 1 • VIDEO: Object Agnosia 2: Impaired Visual but not tactile identification (naming), subject 2 • VIDEO: Object Agnosia 3: Intact visual movement identification, subject 2 • VIDEO: Object Agnosia 1: Impaired Visual identification (subject given name & array of objects), can’t see objects

8. Associative Agnosia Associative Agnosia • Cannot recognize objects by sight alone • Intact general knowledge of objects • Can recognize objects by touch or definition • Visual perception better than in apperceptive agnosia • Not a naming deficit (cannot indicate recognition by nonverbal means)

9. Theories of Associative Agnosia • Disconnection between visual representations and language areas • Disconnection between visual representations and memory areas • Stored visual memories have been damaged • A perceptual and memory problem, and the two are inseparable

10. Intertwined Perception & Memory • Some visual problems • Copying drawings on line by line • On matching tasks, they rely on slow, sequential featured-by-feature checking • In the PDP system, the memory of the stimulus would consist of a pattern of connections strengths among a number of neuron like units. The " perceptual" representation resulting from presentation of the stimulus will depend upon the pattern of connection strengths among the units directly or indirectly activated by the stimulus. Thus, if a memory is altered by damaging the network, perception will be altered as well. Thus, Associative Agnosia may not be the results of an impairment to perception or to memory; rather, the two are in principle inseparable, and the impairment is better described as a loss of high level visual perceptual representations that were shaped by, and embody the memory of, visual experience.

11. Apperceptive:Localization of Damage • Diffuse brain damage, often from • Multiple infarcts or from other global anoxic events: e.g. carbon monoxide poisoning.

12. Apperceptive Associative

13. Associative Agnosia

17. Prosopagnosia

18. Prosopagnosia • Compensate by relying on nonfacial cues (voice, gait, clothing..) • With a few exceptions, they can discriminate a face’s gender, ethnicity, approximate age, and emotion conveyed. • Patients who do not have problems recognizing faces may have difficulty recognizing the emotion.

19. Matching Faces Task

20. Test of Famous Faces

22. Types Of Agnosia • Face • Object • Printed Word • Face, or face and object -- right or bilateral • Word, or word and object – left • Maximum overlap in left inferior medial region (including parahippocampal, fusiform, and lingual gyri)