Visual system Flashcards
Lesions of the optic chiasm result in
Bitemporal hemianopia
LH damage vs. RH damage effects on block design
LH - error with internal details, tend to recognize when incorrect RH - break configuration but see internal details, do not appreciate when incorrect, may skew to right space
Palinopsia
Persistence or reappearance of a recently viewed object; assoc. w/ parietal & occipital lobe lesions
Akinetopsia
Acquired cerebral motion blindness
A lesion of the optic nerve results in
Monocular visual loss or monocular scotomas
Clinical triad of Balint’s syndrome
Simultanagnosia, optic ataxia, ocular apraxia
Metamorphopsia
Condition in which objects have distorted shape & size; aka “Alice in Wonderland” syndrome Associated with disorders of the inferior or lateral visual association cortex
Formed visual hallucinations arise from
Inferior temporo-occipital visual association cortex
How is the pretectum involved in vision?
Changes in pupil size in response to light
Meyer’s loop
Inferior optic radiations that arc forward into the temporal lobe; carry info from the inferior retina or superior visual field
Cortical blindness
Caused by bilateral lesions to the primary visual cortex
Common causes of optic chiasm lesions
Pituitary adenoma, meningioma, craniopharyngioma, hypothalamic glioma
Lesions of the LGN result in
Contralateral homonymous hemianopsia
LH damage vs. RH damage effects on drawing
LH - drawing is spatially correct but oversimplified with omission of details RH - fragmented drawing, may have details but lost whole & spatial relations, may neglect L side
Macula
Oval region that surrounds the fovea
Info from the fovea is represented by what portion of fibers in the topic nerve?
~1/2
Blindsight
Despite lesions of the primary visual cortex & lack of conscious visual perception, some patients are able to perform tasks, appears to depend on info that is transmitted via extrageniculate visual pathways
Face/object recognition is localized to the
Midportion of the fusiform gyrus
The retina is supplied by what artery?
Ophthalmic
Anton’s syndrome
Syndrome in which patients with cortical blindness deny blindness & confabulate visual images
Dorsal visual stream
“where”, info regarding spatial analysis & orientation; runs along top side of cerebrum from occipital to parietal visual areas
An inability to recognize facial emotion is associated with lesions to the
Bilateral amygdala
Lesions of the lower/upper optic radiations result in
Lower - contralateral superior quadrantanopia Upper - contralateral inferior quadrantanopia
Neuroanatomical correlate of Balint’s syndrome
Bilateral lesions to dorsolateral parieto-occipital cortex, most often MCA-PCA infarcts
The “what” visual stream is supplied by what artery?
PCA
Fortification scotoma
Visual blurring & scotomas with scintillating appearance or that consist of jagged alternating light & dark zigzag lines; seen in migraine
Off-center receptors
Inhibited by light in the center of the receptive field & excited by light in the surrounding area
Release phenomenon
Pts with visual deprivation in part or all of their visual fields caused by either ocular or CNS lesions may see objects, people, or animals in the region of visual loss
STS stream
“specialized movement”; visual analysis of mvmt of body parts & biological objects; located in the superior temporal sulcus
Amaurosis fugax
TIA of the retina
Ventral visual stream
“what”, info regarding shape, pattern; runs along underside of cerebrum from occipital to temporal visual areas
Charles Bonnet syndrome
Visual hallucinations following loss of vision due to cataracts, glaucoma, or age-related macular degeneration; may be simple or complex
Optic disc
Region where axons leaving the retina gather to form the topic nerve
The “where” visual stream is supplied by what artery?
MCA-PCA watershed area
P cells
Have small receptive fields, sensitive to fine visual detail & colors, project to parvocellular layers of LGN
Lesions of the upper/lower banks of the calcarine fissure result in
Upper - CL inferior quadrantanopia Lower - CL superior quadrantanopia
On-center receptors
Excited by light in the center of the receptive field, inhibited by light in surrounding area
Lesions of the entire calcarine fissure result in
CL homonymous hemianopia
Bilateral lesions of the middle temporal gyrus result in
Akinetopsia - can’t perceive visual motion
What percentage of retinal input is relayed to the striate cortex via the LGN?
70%
Tectopulvinar pathway
Optic tract => superior colliculus => pulvinar => other visual cortical areas
Lesions to the dorsal visual association pathway will result in
Visuospatial disorientation syndromes (visual neglect, dressing apraxia, simultanagnosia, Balint’s)
Geniculostriate pathway
Optic tract => LGN => striate cortex
M cells
Have large receptive fields, respond best to gross stimulus features & mvmt, project to magnoscellular layers of LGN
Center-surround
Concentric receptive fields
Lingula
Area below the calcarine fissure
Hering’s opponent process theory of color vision
3 pairs of receptors: red/green, yellow/blue, white/black; excitation of one inhibits the other
Young-Helmholz trichromatic theory of color vision
Red, blue, green receptors in the retina
Cuneus
Area above the calcarine fissure
What type of visual phenomena may be seen in occipital seizures?
Pulsating color lights or moving geometric shapes
A man with a history of glaucoma complains of well-formed visual hallucinations. What is the name of this syndrome?
Charles Bonnet Syndrome
