Agnosias And Neglect Flashcards
The What system
The ventral processing system, higher aspects of visual object recognition: connects visual perception of shape and form with the representation of the objects meaning
Left and right components of the occipital to temporal pathway, in the What system
Left: letters and numbers
Right: objects and faces
The Where system
Dorsal processing system, works with objects’ locations in relation to the self and other objects. Helps plan and coordinate motor movements
Where system pathway
Occipital to parietal
What is a visual agnosia?
Lack of access to knowledge about objects, where one can see an object but not know what it is.
Apperceptive agnosia
Difficulty with object perception, an inability to use components to synthesize a full image
Testing for apperceptive agnosia
Copying and matching objects, discriminating shapes
Lesion site and cause for apperceptive agnosia
Right parieto-occipital area, often caused by carbon monoxide poisoning
What is associative agnosia?
Loss of knowledge of semantic meanings of objects, there is difficulty accessing concepts but not words
Testing for associative agnosia
Can draw, match and discriminate objects, but can’t name objects
Lesion site and cause of associative agnosia
Bilateral damage to the temporo-occipital junction and subjacent white matter. Caused by bilateral primary carotid artery stroke
Definition of prosopagnosia
Agnosia for faces, can see and recognize emotions and match faces and distinguish age and gender but can’t distinguish individual faces
Lesion site for prosopagnosia
Bilateral damage to the fusiform gyrus
Left vs right debate
Left: deficits in symbolic spatial cognition (left right disorientation, finger agnosia, map reading, compass reading)
Right: deficits in concrete spatial cognition (putting on clothes, gauging space between items)
Components of right hemisphere syndrome
- constructional apraxia
- neglect
- anosognosia
- left hemiplegia or hemiparesis
What is neglect?
Loss of conscious awareness of an aspect of spatial or personal space
Most common neglect?
Left side of space, found with right hemisphere lesions to the parieto-occipital or inferior parietal region. Thalamic, subcortical lesions
Common cause for neglect
Right side major carotid artery stroke
Description of neglect
It extends beyond the body, to the entire left side. It’s more than just sensory loss on that side, it’s like a lack of attention
Presentation of neglect
- no attention to the left side of space or of objects
- gradient of neglect, not a clear cut line
- allothesia (transferring stimuli to the right)
- multimodal
Extinction test for neglect
Eyes closed –> right stimulus –> left stimulus –> both stimuli
Only the right side is noted
