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63 Cards in this Set
- Front
- Back
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True or false: The optic nerve is part of the diencephalon |
True |
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What is the fovea? |
The region of the retina with the highest visual acuity. |
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What is the macula? |
An oval region approximately 3 x 5 mm that surrounds the fovea and also has high visual acuity |
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What photoreceptor is the most prominent in the macula and fovea? |
Cones: Which have high spatial and temporal resolution and they detect colors. |
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What photoreceptor is the most prominent in the macula and fovea? |
Cones: Which have high spatial and temporal resolution and they detect colors. |
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What are rods? |
Photoreceptors that are sensitive to low-level lighting. |
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Which type of photoreceptors are the most prevalent within the eye? |
Rods are far more numerous by ratio of about 20:1. |
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What is the name of the area on the retina where axons gather to form the optic nerve? |
The optic disc. This is a physiological blind spot. |
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How are rods and cones distributed throughout the retina? |
Rods are more prevalent along the periphery of the retina, and cones increasing prevalence as you approach the macula. |
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What is the relationship between optic nerves, the optic chiasm, and optic tracts? |
Optic nerves are pre-chiasmatic, the optic chiasm is where the nerves connect and partially decussate, optic tracks are post chiasmatic and travel to the lateral geniculate nucleus (with some fibers going to superior colliculus). |
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Which axons from the retina crossover at the optic chiasm? |
The axons originating on the nasal side. This is why lesions of the optic chiasm lead to bilateral lateral (bitemporal) visual field loss. |
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What is the largest sulcus of the occipital primary visual cortex? |
Calcarine fissure |
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How many layers are there in the lateral geniculate nucleus? |
Six. Layers 1, 4,&6 receive inputs from the contralateral eye.
Layers 2,3,& 5 receive input from the ipsilateral eye. |
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Why do some fibers from the optic tract travel to the superior colliculus? |
For visual reflexes and alerting attention. |
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Define scotoma |
A circumscribed region of visual loss.
Usually used to refer to what is observed following a lesion to the retina itself. |
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What type of visual loss results from a lesion to an optic nerve? |
Monocular visual loss.
This is often seen with demyelination in multiple sclerosis. |
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What arteries run alongside the optic chiasm? |
The carotid arteries.
Lesions involving the carotid arteries damage to lateral sides of the optic chiasm. This is what leads to medial visual field loss because the nasal projections from the retina are preserved on the inside of the Chiasm |
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What arteries run alongside the optic chiasm? |
The carotid arteries.
Lesions involving the carotid arteries (like carotid calcification) damage the lateral sides of the optic chiasm. This is what leads to bilateral medial visual field loss (binasal defect) because the nasal projections from the retina are preserved on the inside of the Chiasm. |
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What structure runs near the central part of the optic chiasm? |
The pituitary gland.
Pituitary tumor can lesion the central chiasm, thus damaging the nasal retinal projections from both eyes. This leads to bilateral loss of the lateral visual fields (bitemporal defect). |
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What type of visual loss is observed in lesions of an optic tract? |
Contralateral homonymous hemianopsia |
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What type of visual field defect is observed if the superior (parietal) optic radiations are lesioned? |
Inferior contralateral quadrantanopsia |
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What type of visual field defect is observed if the superior (parietal) optic radiations are lesioned? |
Inferior contralateral quadrantanopsia |
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What type of visual field defect is observed if the superior (parietal) optic radiations are lesioned? |
Inferior contralateral quadrantanopsia |
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What type of visual field defect is observed if the inferior (temporal) optic radiations are lesioned? |
Superior contralateral quadrantanopsia |
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What is the gyrus superior to the calcarine fissure called? |
Cuneus gyrus |
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What is the gyrus inferior to the calcarine fissure called? |
Lingual gyrus |
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Describe the retinotopic map of the primary visual cortex. |
Macula is most posterior, and has redundant blood supply. This is what accounts for macular sparing when the more anterior visual cortex is deprived of blood (since it does not have redundant blood from MCA & PCA). |
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What percentage of the visual cortex is dedicated to the fovea? |
50% |
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What is the function of the dorsal pathway or stream? |
To analyze motion and spatial relations (where?). These are projections from the visual cortex to the parieto-occipital association cortex. |
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What is the function of the ventral pathway or stream? |
Analysis form and color (What?). These are projections from the visual cortex to the temporal-occipital association cortex? |
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What Brodmann area numbers are associated with the primary and secondary visual cortex? |
17: primary visual cortex 18: secondary visual cortex |
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What is another name for the primary visual cortex? |
The striate cortex |
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What controls searching eye movements? |
Frontal eye fields. |
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What controls searching eye movements (i.e., saccades)? |
Frontal eye fields. |
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What controls tracking eye movements (i.e., smooth pursuit)? |
Occipital eye field |
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Which cranial nerves affect eye movement? |
3, 4, & 6 These also are connected to vestibular system and manage vestibulooccular movement |
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What structures are responsible for the convergence of eye movement? |
Cranial nerves |
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What disorders are produced by lesions to the ventral stream? |
Visual agnosias |
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What are visual agnosias? |
The inability to recognize objects or appreciate their meaning. A precept stripped of its meaning |
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What are the 3 categories of visual agnosia? |
1. Visual object agnosia 2. Prosopagnosia 3. Color agnosia |
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What are the two types of visual agnosia? |
Apperceptive agnosia Associative agnosia |
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What is the difference between Apperceptive and Assoicative agnosia? |
In APPERCEPTIVE agnosia, Patients are unable to draw the object on command,copy the object on paper, or match similar classes of objects together.
In ASSOCIATIVE agnosia, the patient can draw or match similar visualobjects together, yet still be unable to name or demonstrate the use of theobjects. |
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What is Balint's Syndrome? |
A rare syndrome with 3 features: 1. OPTIC ATAXIA 2. OCULAR APRAXIA 3. SIMULTANAGNOSIA |
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What is optic ataxia? |
The inability to coordinate hand-eye movements. Patients have trouble reaching for targets in space. |
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Define ocular apraxia? |
The loss of voluntary ability to shift gaze despite intact cranial nerves.
Looks like a psychic stare, but the patient can move eyes if they are closed. |
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What is the lesion associated with Balint's Syndrome?
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White matter underlying ANGULAR GYRUS
Bilateral occipitoparietal lesions
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What is ocular dysmetria?
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Saccadic problem where eyes over and undershoot targets, or move back and forth when trying to focus on target |
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What is Todd's Syndrome (Alice in Wonderland)? |
1. Alteration in perceptions of time 2. Dysmetriopsia where object seem small (micropsia), large (telopsia), too close (pelopsia), or distorted (metamorphsia). |
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What lesions lead to prosopagnosia? |
Bilateral inferior occipito-temporal junction or inferior occipito-temporal junction When unilateral, right hemisphere inferior longitudinal fasiculus and splenium of corpus callosum. |
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What lesion causes color agnosia?
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Left or bilateral medial occipital-temporal region.
Or
Primary visual cortex extending to corpus callosum! ASSOCIATED WITH ALEXIA WITHOUT AGRAPHIA!!!!!!!!!!! |
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What lesions lead to visual agnosias?
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Left occipital or bilateral peristriate lesions of angular gyrus and lingual or fusiform lobules. |
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What lesions lead to constructional apraxia?
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Right parietal and bilateral parietal
Disrupts both frontal and parietal systems |
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What lesions lead to achomoatopsia? |
Calcarine fissure lesions (more on the left than right) lead to partial achromatiopsia.
Fusiform gyrus lesions lead to total achromatiopsia AND prosopagnosia. |
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What lesion is associated with dressing apraxia? |
Right parietal-occipital region |
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What lesions are associated with simultanagnosia? |
Bilateral Parieto-occipital lesions |
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What is astereognosia? |
An inability to recognize an object by touch.
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What is somatognosia? |
Inability to have knowledge and sense of one's own body. |
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What is apraxia of speech? |
NOT DYSARTHRIA. It is articulation errors from poor motor planning of speech movements. |
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What is buccofacial apraxia? |
Inability to carry out voluntary skilled motor movements of the face, tongue, or lips. |
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What is gait apraxia? |
Loss of ability to use legs for walking in spite of the ability to demonstrate correctly walking when lying flat |
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Where are the lesions for ideational apraxia?
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Frontal lobe lesions |
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Where are the lesions for ideomotor apraxia?
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Splenium of corpus callosum
Left inferior parietal lobule
Dominant hemisphere |
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What other condition can accompany achromotopsia? |
Prosopagnosia BOTH ARE DUE TO FUSIFORM GYRUS DAMAGE |
