Visual Systems Flashcards
How is the retina dividd into quadrants?
nasal and temporal hemiretinas, then upper and lower: 4 quadrants
What order neurons are the ganglion cells?
third order - but they synapse on the LGN of the thalamus - making it different from the somatosensory pathways
Are damages to the visual pathway usually rnamed accoridng to the affected visual field or retinalf ield?
visual
What is a hallmark of binocular visual field?
both eyes contribute to each visual field - this is why having the fields go to the contralateral cortex is important
THe nasal retina gets information from the ___ field
the temporal field!
So nerves carrying information about the ___ field from the ____ retina will cross as the optic chiasm
nerves carrying information form the temporal field at the nasal retina will cross at the chiasm
WHy is the location of the optic chiasm clinically significant?
it’s located just anterior to the pituitary gland, so pituitary tumors will compress the chiasm, creating a loss of TEMPORAL FIELDS!
What part of the retina receives information from the upper visual field?
the lower half of the retina
What is the difference between homonymous and heteronymous damage?
homonymous = defects involve one visual field
heteronymous = defects involve parts of both visual fields, so defects are non-overlapping = these occur at the chiasm!
Where do most axons from the retinal ganglion cells terminate?
the lateral geniculate nucleus
Each LGN receives information from only one _____
visual field (contralateral)
Each LGN is divided into 6 layers, each receiving information from only one____
eye
Describe the retinotopic mapping of theLGN
THe medial half of the LPN is from the lower visual field while the lateral half is form the upper visual field
The central 2/3 of the LGN are devoted to the macula, then it’s to the nasal retinal, then the otuer portion is to the temporal retina
What are the three other locations axons can project to besides the LGN? FOr what purpose?
- reticular fibers of hypothalamus = regulation of circadian rhythm
- Pretectum = reflexive control of pupils and lens
- Superior colliculus = orienting movements of head and eyes
What is another term for the optic radiation?
geniculocalcarine tract
What are the two pathways within the geniculocalcarine tract and what info do they carry?
sublenticular = fibers from the upper visual field travel through the temporal lobe as meye’rs loop
retrolenticular = fibers from lower visual field travel direclty thorugh the parietal lobe to the occipital cortex
If you damage meyer’s loop, you lose vision in the ___ visual field of the contralateral field.
upper
THe primary visual cortex surrounds the ___ fissure separating what two gyri?
the calcarine fissue between the lingual gyri (bottom) and the cuneate gyri (top)
The upper visual field projects to the ___ gyrus
the lower visual field projects to the ___ gyrus
upper visual field = lingual gyri (lower one)
lower visual field = cuneate gyri (upper one)
Where in the primary visual cortex is macular representation?
the most caudal 1/3 of the area is for the macula, while the peripheral fields get the most rostral 2/3 (temporal most rostral, nasal in the middle)
what types of information are responded to in the primary visual cortex?
color
location
shape and motion
Stroke to the visual cortex will result in contralateral field loss, with what special feature?
macular sparing
What sorts of visual information does the visual association cortex deal with?
complexity of vision like object recognition, hand-eye coorination, eye movements, etc.
What are the two association cortex projection streams?
dorsal stream and ventral stream
dorsal = to the parietal and upper temporal = the “where” (location, movement, position)
ventral = projections to inferior temporal cortex= “what” (form, color, oject recognition, memroy)
