1. LOGO 지각장애

2. Perception Percepts o Individuals capable of receiving information of sensation o Data  meaningful, comprehensible Perception o Percepts processing of the data to represent reality

3. Disorders of Perception Sensory distortion o A real perceptual object is perceived in a distorted way. o Changes in perception due to changes in the intensity, quality of the stimulus or spatial form Sensory deception o New perception occurs. o This may or may not be in response to an external stimulus.

4. Sensory distortion Change in intensity o Hyperaesthesia - due to intense emotions or lowering of physiological threshold - ex) anxiety, depression, alcohol withdrawal o Hypoacusis - Threshold for sensations is raised Change in quality o Mainly visual perceptions are affected o Caused by toxic substances Change in spatial form o Change in perceived shape of an object

5. Sensory deceptions Illusions o Misinterpretation of stimuli from an external object o Visual illusions are most common o Not in themselves indicative of pathology Hallucinations o Perception without an object o Perception in the absence of external stimulus that has qualities of real perception.

6. Things that can go wrong with visual perception that cannot be characterized as simple absolute visual field defects. Extra- striate cortex, ‘visual association cortex’, ‘higher order’ visual deficits. Visual perception is all about analyzing different aspects of an image, not just getting a picture into the head! There are multiple parallel systems that analyze different aspects of a visual scene. Disorders of Visual Perception

7. Visual Object Agnosia The impairment of object recognition in the presence of relatively intact elementary visual perception, memory, and general intellectual function. Farah & Feinberg, 1997

8. Agnosia Apperceptive: lack of recognition because of impaired (higher order) visual perception. Associative: lack of recognition because of lack of association of percept with its meaning. Lissauer 1890 per Farah & Feinberg, 1997

9. Apperceptive Agnosia Basic acuity and visual fields preserved: o Good acuity, o Brightness discrimination, o Color vision, and o Other elementary visual capabilities However, cannot distinguish between or recognize different visual shapes Cannot copy (draw) shapes

10. Apperceptive Agnosia Apperceptive agnosias often occur after carbon monoxide poisoning or other diffuse toxic effects. Subtypes include: dorsal and ventral simultanagnosia, and visual hemi-neglect.

11. Associative Agnosia Visual perception relatively preserved but not visual object recognition. “Recognition without meaning” o Can copy shapes (drawing) o Can recognize from verbal description or non-visual sense o Can recognize by feel or verbal description o Cannot indicate visual recognition by non-verbal means (Not the same as Optic Aphasia, which is the ability to name from description and palpation but a specific inability to name visually-presented objects.)

12. Simultanagnosia Impairment in perception of multi-element or multipart visual displays. (e.g., piecemeal description of a complex picture. May fail to interpret overall scene.) o Dorsal: Cannot attend to >1 part of object. May act blind as they bump into objects that are close to each other. Have trouble counting. Bilateral Posterior Parietal lesions. o Ventral: Recognition of simple shapes not obviously impaired. (letter by letter reading). Don’t bump into objects i.e. don’t act blind. Can count, so can actually ‘see’ more than one object. But don’t see the whole picture in a scene, and can’t identify more than one object at a time. L inferior temporo-occipital cortex

13. Prosopagnosia “The man who mistook his wife for a hat” Προςοπόν (prosopon) = face, agnosia = non-knowledge. Usually aware of deficit. Sometimes called “Face blindness” Rely on non-facial cues (voice, gait, clothing) Can discriminate some qualities (gender, race, ~age, emotional expression!)

14. Prosopagnosia Superior temporal sulcus has strong connections with the amygdala. Injury can cause a severe deficit in comprehension of facial expressions and gaze directions. Adolphs et al. 1994, Young et al., 1995 Can be secondary to PCA infarct encroaching on medial cortex of occipital and temporal lobes and the inferior longitudinal fasciculus (i.e., occipital to temporal projections). Can be associated with Alzheimer’s (and much else). Most strongly associated with the fusiform gyrus: in particular the fusiform face area.

16. Inferior longitudinal fasciculus

17. Superior temporal sulcus

18. Central Achromatopsia Can perceive borders defined by color differences that classic photoreceptor color-blind people cannot (Ishihara test). Pure form is very rare (requires specific bilateral lesions in ventro-medial occipital lobe) A defect in color perception caused by an acquired cerebral lesion. o Reduced hue discrimination o Deficient color constancy o Cannot order colors in a test Colors are either all gray, or “washed out”, “dirty”, or “faded” Problems in imagining colors are reported (Oliver Sachs, colorblind painter) Also known as color agnosia

19. Balint Syndrome Simultanagnosia (independent of object size or visual periphery.) Spatial disorientation: inability to orient, localize, and reach for objects = “optic ataxia” Oculomotor disturbances: fixation, saccade initiation and accuracy, smooth- pursuit. “optic apraxia” = inability to voluntarily move eyes to a new position Damage to posterior superior watershed areas (Brodmann 7 + 19). Multiple strokes, Alzheimer’s, tumors, other injury.

20. Misidentification Syndromes Patient incorrectly identifies and reduplicates persons, places, objects, or events. Capgras Σ: multiple persons (incl. Family) replaced by impostors. Fregoli Σ: a familiar person is impersonating a stranger. Intermetamorphosis: Persons known to the patient have exchanged identities. Delusion of subjective doubles: the patient themselves have been replaced.

21. Capgras Syndrome Also called Capgras Delusion. Named after French psychiatrist Joseph Capgras, wrote a paper about a woman who was convinced that “doubles” had replaced people she knew. It has been proposed that face recognition has both conscious and unconscious parts. Idea that people can recognize the faces, but they associate them with strangers (don’t show appropriate emotional reactions to faces they recognize). Visual processing defect has to be in addition to other cognitive problems (schizophrenia).

22. Fregoli Syndrome Also Fregoli Delusion Named after Italian actor and quick-change artist Leopoldo Fregoli Belief that different people are a single person in disguise. Like Capgras, thought to be a problem with normal face recognition.

23. Reduplicative paramnesia Typically misidentification of places rather than person. A delusional belief that a place or location exists in two places at once. Originally thought to be ‘psychological’, currently the thinking is that it involves disorders of visual spatial processing and memory.

24. Hemi-Neglect Cannot notice or pay attention to visual stimuli on one hemi-field. Can’t even imagine that half the world is even there! Not even black… Usually it’s the left visual hemifield that is neglected (“Eyes Right”), due to a right parietal lesion.