GA: Visual Tracts Flashcards
What is a visual field?
The area a person is able to see when both eyes are fixed in one postion
What is the retinal field?
Location on the retina that an object in the visual field is projected.
Focused + centered on fovea centralis + macula lutea
What zones make up the visual field?
Binocular zone (both eyes - central) + Monocular zone (R/L eye only)
How is the retinal field subdivided?
*image is inverted on retina
Nasal + temporal retinal hemifields –> further divided into quadrants
For example: the left half of the visual field forms an image of ___________.
The nasal (right) half of the left retina
The temporal (right) half of the right retina
How do we describe visual deficits?
Based on the visual field
What comprises the optic tract?
Nasal retina (contralateral eye)
Temporal retina (ipsilateral eye)
*they cross in optic chiasim*
What do you need for depth perception?
Information from both retinas brought together
How is the eye/optic tract organized?
In a retinotopic pattern
Where does the optic tract terminate?
Lateral geniculate nucleus
The magnocellular (M) layer =
input from rods + large receptive fields
sensitive to moving stimuli
The parvocellular layer =
cones
small receptive field
Ganglion cell axons that arise in the temporal retina:
terminate in _______ layers and are __________.
layers 2,3,5
IPSILATERAL
Axons that arise in the nasal retina terminate in ________ layers and are ___________.
1,4,6
CONTRALATERAL
The same point in visual space can be represented multiple times, why?
Cause the optic tract branches in multiple layers (6)
Where does the geniculocalcarine pathway run (optic radiations)?
LGN –> Calcarine sulcus (primary visual cortex)
Fibers from the lower quadrant of the contralateral hemifields (optic radiations) target _______.
Superior bank on cuneus
Fibers from the upper quadrant of the contralateral hemifields (optic radiations) target _______.
Inferior bank on lingual gyrus
Fibers that pass through Meyer loop come from where?
Upper quadrant of the contralateral hemifields (optic radiations)
Fibers conveying information from the macula + fovea go to?
Caudal portions of the visual cortex
Retinogeniculocalcarine pathway
Because of Meyes loop, what can temporal lobe damage produce?
Sometimes a superior visual field deficit
Objects in either half (L or R) of the visual field produce images upon the nasal hemiretina of the ips. eye + the temporal hemiretina of the cont. eye.
This is an example of?
Retinotopic Organization
Where does the visual pathway end?
Brodmann’s area 17 (primary visual cortex/striate cortex)
Areas 18,19, plus parts of the temporal + parietal lobes =
Visual Association cortex (parieto-occipito-temporal area)
name these areas:
What is the superior colliculus important for?
Directing eye movements
What is the pretectal area important for?
Pupillary light reflex
Review pupillary constriction reflex
What is hemianopia?
Blindness in 1/2 of visual field
What is quadrantanopia?
Blindness in one quadrant of the visual field
What is homonymous visual fields?
Conditions in visual field losses are similar in both eyes
What is heteronymous visual fields?
Conditions in which the two eyes have non-overlapping field losses (don’t match)
What is macular sparing?
Visual field loss that preserves vision in the center of the visual field
An anterior lesion in the optic tract is more likely to be?
Incongruous (non symmetrical in both eyes)
A lesion close to the visual cortex makes it likely to be?
Congruous (symmetrical in both eyes)
Damage anterior to the optic chiasm affects:
Ipsilateral eye
Damage @ the optic chiasm causes?
Heteronymous deficits
Damage behind the optic chiasm causes:
Homonymous deficits
What is associative visual agnosia?
Patient cannot name or describe an object in the visual field, BUT he can recognize + demonstrate its use
