Agnosias Flashcards
Color aphasia
Disproportionate difficulty in linguistic processing of colors associated with dominant parietal damage
Neuroanatomical correlate of associative visual object agnosia
Bilateral, inferior occipito-temporal; commonly see with R HH, strokes in PCA
Neuroanatomical correlate of color anomia
L occipitotemporal mesial lesion/lingual gyrus, extending into CC
Ellis & Young’s model of object recognition
Recognition by comparing viewer-centered & object-centered representations to stored structural descriptions of objects known as “object recognition units”
Neuroanatomical correlate of pure word deafness
Associated w/ B symmetrical lesions of anterior section of the superior temporal gyri; disconnection of Wernicke’s from auditory input
Agnosia
Modality-specific inability to access semantic knowledge of an object or other stimulus that cannot be attributed to impairment of basic perceptual processes
Bilateral astereognosis
Inability to judge the form of an object by touch; cannot demonstrate object knowledge through gesture
Neuroanatomical correlate of apperceptive visual agnosia
B damage to lateral parts of the occipital lobes
Autotopagnosia
Inability to identify body parts (e.g., finger, also L-R confusion), associated with lesions in the dominant parietal lobe
Apperceptive visual object agnosia
Difficulty recognizing objects b/c of failure to perceive them; can’t draw, copy, or match
Neuroanatomical correlate of color agnosia
B lesion of the ventral visual stream
Unilateral astereognosis
Can demonstrate object use or can name if object is placed in other hand; associated with CL primary somatosensory projection area damage
Neuroanatomical correlate of associative prosopagnosia
Bilateral anterior temporal regions compromising hippocampal & other regions
Ahylognosia
Impaired discrimination of distinctive qualities of objects such as density, weight, texture, heat
Bisiach et al.’s domain-specificity of anosognosia
Pts who are blind due to peripheral lesions are aware of their deficits & behave like a blind person; pts w/ central lesions have an associated visuo-specific cognitive impairment-monitoring deficit
Visual object agnosia is associated with damage to the
L unilateral or B occipitotemporal (lingual, fusiform, & parahippocampal gyri) areas
Associative agnosia
Elementary visual perception is more or less preserved but access to memory or meaning is impaired
Balint’s syndrome
Simultanagnosia, ocular apraxia, optic ataxia Caused by large B parietal lesions, esp. if frontal lobes affected
Semantic-associative auditory sound agnosia
Primarily symantic misidentifications of nonspeech sounds (‘train’ for automobile engine); associated with LH lesions (perceptual-discriminative is R)
Lissauer’s two-stage model of perception/recognition
After an elementary sensation occurs there is 1) an object perception (apperception) & 2) object recognition (association)
Marr’s model of 3 types of representation
1) primal sketch (depicts brightness/darkness) 2) 2.5D sketch (viewer-centered) 3) 3D sketch (object-centered)
What visual impairment is commonly comorbid with associative agnosia?
Right HH
Neuroanatomical correlate of phonagnosia
Unilateral RH pts demonstrate difficulties with familiar voices; temporal lobe impairment in either hemisphere can lead to more general voice discrimination
Geschwind’s disconnection theory of anosognosia
RH is normally poorly linked to speech areas, further weakened by RH damage; confabulation is LH attempt to explain what pt can’t comprehend
Pure word deafness
Unable to comprehend spoken language with relatively spared comprehension of nonverbal sounds
Color anomia
Loss of color naming, often in conjunction with alexia w/o agraphia, assoc. w/ R HH
Apperceptive agnosia
Deficits in the early stages of perceptual processing; pats do not perceive objects normally so can’t recognize them
Prosopagnosia is associated with what other deficits?
Color agnosia, L upper quadrantanopsia
The term agnosia was originally coined by
Freud (1891)
Achromatopsia is associated with what other conditions?
Visual agnosia & prosopagnosia
Neuroanatomical correlate of apperceptive prosopagnosia
Bilateral cortex & WM in occipito-temporal gyrus, typically including the fusiform face area
Pathological processes that may be associated with apperceptive visual agnosia
CM poisoning, mercury, cardiac arrest, B strokes, B artery occlusion, B posterior cortical atrophy
Amorphognosia
Impaired identification of an object by proprioception/recognition by size & shape
Optic aphasia
Visually presented objects can be recognized by not named, & auditory & tactile naming ok
Phonagnosia
Inability to recognize familiar persons’ voices
Associative visual object agnosia
Pts demonstrate that they can perceive but not recognize; can draw or match
Ocular apraxia
An inability to shift gaze voluntarily from a fixation point; pts behave as though mesmerized by original object; gaze may be shifted if close eyes
Pure word deafness may evolve from what type of aphasia?
Wernicke’s
Damasio’s model of agnosia
Perception involves evocation of neural activity pattern in primary & 1-st order association cortex which corresponds to various perceptual features; downstream features are combined in ‘local convergence zones’ Predicts that there can be no disorder of object recognition w/o perceptual dysfx
Conscious awareness system (CAS; Schacter & McGlynn)
Conscious experience of remembering, knowing, perceiving, comprehending; requires activation of specific/distinct system which interacts w/ modular systems concerned with specific function Low activation of normally highly activated system would result in no input to the CAS => anosognosia
Tactile asymboly
Impaired tactile recognition of objects with intact perception of size, shape, density, weight, texture, heat
Neuroanatomical correlate of achromatopsia
Unilateral or bilateral lesions to the ventromedial region of the occipital lobe with involvement of the lingual & fusiform gyri (i.e., visual association cortex)
Amorphognosia
Inability to identify an object by proprioception due to poor perception of its physical attributes; cannot be explained on the bases of concurrent hypesthesia
Sensory amusia
Unable to appreciate various characteristics of heard music due to unilateral temporal lobe lesion
Perceptual-discriminative auditory sound agnosia
RH analogue to pure-word deafness; primarily acoustic misidentifications of nonspeech sounds (‘whistling’ for bird-song)
Optic ataxia
Impairment of visually guided movements as a result of a defect in stereopsis (depth perception); pts may not be able to read in methodical visual sweeps
Dorsal vs. ventral simultanagnosia
Dorsal = cannot see >1 object at a time caused by bilateral parieto-occipital lesion Ventral = cannot appreciate entire stimulus; cannot attend to whole picture; caused by damage to the left inferior temporo-occipital area Part of Balint’s syndrome
What type of amnesic syndrome is more likely to be associated with anosognosia?
Diencephalic/frontal lobe damage but not mesial temporal lobe damage/thalamic damage
Achromatopsia
Loss of color vision due to CNS disease, but can name color of object described verbally
Auditory affective agnosia
Impaired comprehension of prosody; assoc. w/ R temporoparietal lesions & neglect
Disconnection model of agnosia
Agnosia results from disconnection between visual & verbal processes (this theory can’t account for fact that most agnosics show abnormal verbal & nonverbal processing of viewed objects)
