Neuro: Visual System Flashcards
Lesions to the retina and optic nerve produce unilateral damage UNLESS the damage is where?
The junction of the optic nerve and optic chiasm
What defects do medial chiasm lesions produce?
Bilateral defects
What defects for lateral chiasm lesions produce?
Unilateral defect unless there is damage on both sides (laterally)
What is the retinotopic map and what is its importance?
The retinotopic map shows the precise arrangement of photoreceptors and retinal receptive fields and are used to determine lesion locations based on VF
What is the “what” pathway involved with?
Form and color
What is the “where” pathway involved with?
Motion and spatial analysis
What is the function of the suspensory ligament of the lens (zonule of zinn)?
Aid in focusing on near and far objects
What is retinitis pigmentosa (very general)?
Rod cells lose their function and over time can cause complete blindness by affecting both rods and cones but the pupillary light reflex remains
What is one of the main features seen in patients that can increase their risks of AMD?
Drusen
What does damage to the retina often cause?
A scotoma
What artery aneurysm can cause damage to the lateral optic chiasm?
Internal carotid artery
Damage in what location can mimic the defects seen in a lateral optic chiasm lesion?
Damage to the lateral optic nerve
Damage to the medial optic chiasm is most often due to a pituitary gland tumor, but can also be due to an aneurysm of which artery?
Anterior communicating artery aneurysm
Which artery causes a lesion in the optic tract?
Occlusion of the anterior choroidal artery
If there is damage to the LGN, what artery is likely responsible?
An occlusion of the posterior choroidal artery
If the VF looks like this on both eyes, what artery is causing the defect, and to which region?
Posterior choroidal artery, LGN
If the VF looks like this in both eyes, which artery is causing the defect, and to which region?
Anterior choroidal artery, LGN
If pt has loss of vision in one eye, and full vision in the other, where is the defect likely located?
The optic nerve
If the pt presents with a binasal hemianopsia, where is the damage likely located?
Lateral optic chiasm
If a pt presents with a bitemporal hemianopsia, where is the issue likely occurring?
Medial optic chiasm
If a pt has loss of half of the right VF in both eyes, where is the issue likely located?
Could be the optic tract or LGN (said we should consider it to just be LGN issues for our cases)
What is the magnocellular system?
The “where” system, located mostly in the periphery and responsible for motion and gross spatial features
What is the parvocellualr system?
The “what” system located mostly central and is responsible for distinguishing form and color
What layers of the LGN do the magnocellular system project to?
1 and 2
What layers of the LGN does the parvocellular system, project to?
Layers 3-6
What is the retinotectal projection responsible for?
The pupillary light reflex
Where is the retinohypothalamic projections and what is it responsible for?
Suprachiasmatic nucleus, pupillary dilation
What are the retinocollicular projections and what are they involved with?
Projections to the sueprior colliculus, visual reflexes
Superior radiations are responsible for which region in the VF?
Inferior VF
Superior radiations run through the ___________ lobe and pass the _________ and end in the ____________________
Parietal lobe, cuneus, superior calcarine sulcus
Inferior optic radiations are responsible for which region of the VF?
Superior visual field
Inferior radiations run through the _______ lobe and end in the ____________
Temporal lobe, inferior calcarine sulcus
Myers loop is involved with which optic radiation and lobe? Damage will cause what?
Inferior radiations, temporal lobe, loss of contralateral superior VF
Baums loop is involved with which radiation and rings through which lobe? Damage will cause what?
Superior radiations, parietal lobe, contralateral inferior VF
Infarct to the middle cerebral artery can affect which regions?
LGN, optic tract, and radiations
Damage to the posterior cerebral artery often causes what VF defect?
Contralateral homonymous hemianopia with macular sparing
What causes the macula to be spared?
Dual perfusion by posterior cerebral artery and middle cerebral artery
Does ventral stream damage affect the what or the where?
The what
Does dorsal stream damage affect the what or the where?
The where
What happens in people with damage to the “what”?
They cannot recognize objects but they can appropriately coordinated their movements to pick the object up
What happens in people with damage to the “where”?
They can recognize objects but are unable to pick them up
What is homonymous hemiachromatopia and what area is affected?
Contralateral color blindness, ventromedial occipital cortex
What is homonymous hemikinetopsia and where is the damage?
Contralateral motion blindness, parietal-occipital-temporal area
What is prosopagnosia and where is the damage?
Inability to recognize faces, occipitotemporal/fusiform gyrus
When there is damage to the right parietal cortex after MCA lesion, what often happens?
Left neglect
What is neglect?
When a patient will suppress or neglect part of an image due to in the brain
When does right neglect occur?
Only in severe cases
