Von Bartheld- Vision II Flashcards
What is considered the “gateway to the cortex”?
lateral geniculate nucleus
What are the four CNS targets of retinal ganglion cells?
lateral geniculate nucleus (LGN)
pretectum
hypothalamus
superior colliculus
Why would retinal ganglion cells want to target the pretectum?
for the pupillary light reflex
Why would retinal ganglion cells want to target the hypothalamus?
for circadian rhythm
Why would retinal ganglion cells want to target the superior colliculus?
visual reflexes; eye and head movements
What is the major target of ganglion cell axons in the optic tract in the diencephalon?
the dorsal lateral geniculate nucleus of the thalamus
How do neurons of the dorsal lateral geniculate nucleus of the thalamus send their axons to the cerebral cortex?
via a part of the internal capsule called the optic radiation and then terminates in the primary visual cortex (V1) or striate cortex of the calcarine fissure in the occipital lobe
What happens if you damage your retinogeniculostriate pathway (primary visual pathway)?
serious visual impairment
What does the edinger wesphal nucleus carry?
preganglionic parasympathetics
Explain how you get constriction of pupils?
light->bilateral projections from retina go to pretectum (b/w thalamus and midbrain). Pretectal neurons project to edinger westphal nucleus in the midbrain->sends its parasympathetic preganglionics to ocuolomotor nerve (CN 3) to terminate on neurons in ciliary ganglion. Neurons of ciliary ganglion innervate the constrictor muscles of the iris which decreases diameter of pupil when activated….. SO when you shine a light in someones eye it constricts!
Why do you get bilateral constriction of pupils when you shine a light in someones eyes?
because your pretectal neurons send axons to BOTH Edinger westphal nuclei!
Where is the suprachiasmatic nucleus located and what does it do?
Base of diencephalon, circcadian rhythm
Where is the superior colliculus and what does it do?
midbrain, coordinates head and eye movements
Explain sympathetic control of pupil dilation
retina tells pretectum which tells the superior cervical ganglion to send postganglionc sympathetics up the internal carotid and into the short and long ciliary nerves to innervates dilator pupillae muscle
projections to the lateral geniculate nucleus arise from ganglion cells who specialize mediating what?
richness of visual perception (high acuity, color, motion)
Projections to the hypothalamus and prectum arise from ganglion cells that are only suited for detecting (blank)
luminance flux
Following damage of the visual cortex or lesions of the pathways to the visual cortex what will remain? what has been said to be associated with this?
the subcortical pathway
Blindsight!
What is blindsight?
it is when you cannot see because your visual cortex is damaged or you have a broken visual pathway BUT when given a visual stimuli, patients can guess what it is!!!
What is the binocular visual field?
FP until before peripheral vision
Mixing of the pathways (right and left eyes) does not happen until the level of the (blank). Are the fibers mixed at the LGN?
visual cortex
NO
Explain to me what binocular disparities are
each eye sees an object at a slightly different angle and are constantly compensating to make their focus equal. The disparities are interpreted as differences in depth and are fused.
What is this:
the perception of depth produced by the reception in the brain of visual stimuli from both eyes in combination; binocular vision.
stereopsis
Explain the course of the optic radiation to the visual (striate) cortex
axons carrying info about superior portion of visual field sweep around the lateal horn of ventricle in the temporal lobe (meyers loop) before reaching the occipital lobe. Those carring inferior portion of the visual field travel in the parietal lobe
I.e inferior retinal quadrants give you superior visual field.
superior retinal quadrants give you inferior visual field
Tell me about the fovea and retinotopy
the fovea comprises one of the smallest areas of retinal surface area but makes up half the visual cortex.
V1 is the primary visual cortex. What are the secondary (extrastriate cortices) cortices?
V2, V3, V4, VP, MT
Is there only one retinotopic map?
no there are many
Crossing of nasal retinal ganglion cell axons in the chiasm do what?
Projects the right visual field to the left side of the brain and the left visual field to the right side of the brain
Several circular retinal ganglion cell receptive fields combine to form (blank) on individual neurons in cortex.
elongated fields
How do we get a singular complete image to the cortex?
rods and cons create an image and send it to the retina which will send affarent fibers to synapse in the LGN which will go to the cortex which will create a simple field that unifies all the info
Where do you find the lateral geniculate nucleus (gate keeper for vision)?
thalamus
Neurons in visual cortex respond to distinct stimulus (blank). So what does this mean?
orientation
Means you will be able to process visual information coming at you from all different angles
Neurons in your visual cortex respond greatest to what orientation?
edges and light and dark
The complexity of a response increases as you move closer to the (blank).
SO.. which cells will have the simplest response? Which will have the most complex?
visual cortex
ganglion
hypercomplex
The simple cells of the visual system (such as ganglion and geniculate) will see what kind of stuff? what about more complex cells?
circles/dots (blurry)
bars, edges (sharp)
The complex cells of the visual system are sensitive to what?
movement, binocular vision, sharp edges, orientation
There are distinct pathways of specific retinal ganglion cell types that travel through the (blank) to the visual cortex.
LGN
There are distinct pathways of specific retinal ganglion cell types that travel through the LGN to the visual cortex. What are these three ganglion/ pathways?
Parvocellular
Magnocellular
Koniocellular
What does the parvocellular nuclei provide?
spatial acuity and color
What does the magnocellular nuclei provide?
rapid motion
What does the konicellular nuclei provide?
short wave length cones (Blue light) !
Right eye and left eye go to different (blank) within the visual cortex. Also you have what 2 other kinds of columns? In level four do you still have separate columns for the eyes or are the inputs still segregated?
columns
ipsilateral and contralateral
still segrated
The contralateral and ipsilateral eye columns go to separates spots in layer 4 so you have what kind of vision of layer four?
4
mononoculear
What is signif about layer 4?
you will for the first time ever, have both the right and left fibers in the same layer
When do you get binocular vision?
when you leave 4
Large visual defects are called (blank)
anopsias
Smaller visual field deficits are called (blank)
scotomas
What do you call it if you lose your peripheral vision?
bitemporal (heteronomous) hemianopsia
What do you call it if you lose your left temporal and your right nasal field?
left homonomous hemianopsia
What do you call it if you lose your left temporal superior and your right nasal superior?
left superior quadrantanopsia
What do you call it when call it if you lose both the left temporal and the right nasal field but still have your macula?
Left homonomous hemianopsia with macular sparing
What is maculopathy?
when you have a small black dot in the center
What does it look like if you retinitis pigmentosa?
like you have a dark border around what you see
What are 2 visual field testing techniques?
confrontation field testing (finger testing in each quadrant)
computerized plotting
Where do you have blind spots in your eye?
at the optic disc!
How do you remember the vision pathway for paraysmpathetics?
PREPE (preppy) Eddy is cilly “looking i.e for the visual pathway”
prectectum-> edinger westphal nucleus->pregangionic sympathetics -> CN3 -> ciliary -> constricter muscles
