Exam2Lec6Vision:CentralProcessing Flashcards
What is most of the visual field
Binocular vision
What is the primary projections pathway?
- Retina
- Optic Nerve
- Optic Chiasm
- Optic Tract
- Lateral Geniculate Nucleus
- Optic Radiations
- Striate (Primary Visual) Cortex
Optic nerve axons from the nasal retina cross at the _ _ and joins axons from the _ _ of the other eye
Optic nerve axons from the nasal retina cross at the optic chiasm and joins axons from the temporal retina of the other eye
What makes up the optic tract?
the contralateral and ipsilateral axons together
What receives input from only one eye (left or right) (has 6 layers)
LGN
What makes up the optic radiations? Where are the optic rad. projected?
- Axons from the LGN
- striated cortex(V1)
Which optic nerve axons cross at optic chiasm? (nasal or temportal)
NASAL, temporal stays ipsilateral
What is the hypothalamus for?
- regulation of circadian rhythms (wake/sleep cycle)
light info
What is the pretectum for?
reflex control of pupil and lens
What is superior colliculus for?
- orienting the movement of head and eyes
how is the lateral geniculate nucelus organized?
left and right LGN are organized into six distinct layers
LGN-> mono or binocular?
monocular! there is no intergration for depth or mvt at the thalmas
The LGN layes recieves what?
retinal ganglion cell inputs from either the left or right eye but NOT BOTH
What is not there in the LGN
binocular processing
What is preserved in the LGN
retinal receptive fields
What are the three retinal ganglion cells that project to LGN locations
- Parvo-cellular (P) ganglion cells
- Magno-cellular (M) ganglion cells
- Koniocellular (K) ganglion cells
- What layers do P ganglion cells project?
- What are their characterics?
- What do they carry and respond to?
- project into layers 3-6
- Small cell body/dendritic morphology
- DO carry color information
- Respond to sustained (not moving) stimuli
Where do M ganglion cells project into?
What are their characteristics?
What do they not carry?
What do they respond to?
- layers 1 and 2
- Large cell body/dendritic morphology
- DO NOT carry color information
- Respond to transient (moving) visual stimuli+low light
more rods than cones
Where do K ganglion cells project into?
What is their charactertics?
What is their role?
- inbetween layers
- very small soma
- fxn is poorly understood-> some role in color perception
projections onto the retina are _ _ and _.
upside down and backwards
Parietal (Superior) Optic Radiations carry information from:
Superior retinal quadrants
Inferior visual field
Temporal (Inferior) Optic Radiations carry information from:
Inferior retinal quadrants
Superior visual field
Where is the meyer’s loop?
Temporal (inferior) optic radiations
How is the striated cortex organized?
binocular/monocular vision/macula and superior/inferior visual fields
What is the magnification factor?
A large cortical V1 region is devoted to processing information from the small retinal foveal (macula) region.
Is inferior or superior visual fields bigger in the striate cortex
superior
has more procesessing space for macula
Like the LGN, how is the striate cortex organized
organized into layers which receive input from either left or right eye
What layer does info enter the striate cortex?
4
What processing do we have after layer 4?
After layer 4 (layers 3, 2, and 1), we then begin binocular visual processing.
How are the layers in the striate cortex dived further? what are they responsible for?
- Layers are further divided into ocular dominance columns
- Responsible for processing orientation of shapes
Neurons in the striate cortex are tuned to what?
specific edge orientation
Within the ocular dominance column, neurons will respond to what? Across a row?
- Within a given column, neurons will respond preferentially to a specific shape orientation.
- Across a row, neurons will respond to varying shape orientation.
- In other words, individual ocular dominance columns are responsible for detecting a singular shape orientation. We combine information across columns to detect changes in orientation.
mapping neurons for orientation preference in V1 primary visual cortex revels _ -type organization
pinwheel
When are we consciously aware of our visual field (conscious perception)
visual cortex (striate)
what are the extrastriate visual cortical areas?
V2, V3, V4 and V5 and MT (middle temporal)
What are the two pathways off the striate cortex (v1)
- WHERE (Dorsal) Pathway
- WHAT (Ventral) Pathway
What is the path for the WHERE (dorsal) pathway and the WHAT (ventral) pathway?
- WHERE: V1 -> V2 -> MT ->Parietal Lobe
- WHAT: V1->V2->V4-> Temporal Lobe
What is the WHERE and WHAT pathway responsible for?
- WHERE: Responsible for spatial recognition (i.e. motion, objects relative to each other in space)
- WHAT: Responsible for object recognition (i.e. faces)
What is an anopsia or anopia?
defect in the visual field
What words do we use to see how much of the visual world is affected?
- Hemi – half of the visual world
- Quadrant – one quarter of the visual world
What words do we use for which part of the visual world is affected?
- Homonymous – on the same side of the visual world (congruent)
- Heteronymous – on different sides of the visual world (incongruous)
What happens when we have damage to the optic nerve ? (ex: right optic n.)
RIGHT Optic Nerve ->Complete loss of information from right eye
* Unilateral Blindness
What happens when we have damage to lateral optic chiasm (what is the offical name)
LATERAL Optic Chiasm -> Unilateral (right) loss of superior + inferior temporal vision
* Incomplete (because only one eye) (contralateral) hemianopsia
What happens when we have damage to central optic chiasm (+ offical name)
CENTRAL Optic Chiasm -> Bilateral loss of superior + inferior temporal vision
* Bitemporal hemianopsia
* Heteronymous because two different fields of the eyes were lost
What happens we have damage in the optic tract? (+offical name)
RIGHT Optic Tract ->Loss of LEFT visual field
* Homonymous (same visual field from both eyes) hemianopsia
What happens when we have damage to the temporal (inferior/meyers loop) optic radiation? (+offical name)
RIGHT Temporal (Inferior/Meyers Loop) Optic Radiation -> Loss of LEFT SUPERIOR visual field
* Homonymous superior quadrantanopsia
What happens when the RIGHT Parietal (Superior) Optic Radiation gets damage (+offical name)
RIGHT Parietal (Superior) Optic Radiation -> Loss of LEFT INFERIOR visual field
* Homonymous inferior quadrantanopsia
What happens when we have complete parito-occipital interruption of the optic radiation (+offical name)
Loss of superior + inferior LEFT visual field w/ macular sparing
* Homonymous hemianopsia
What would happen if we have incomplete damage to the visual cortex?
homonymous (both eyes) scotomas, usually encroaching at least acutely on central vision.
Infarctions can lead to what?
defects in the visual pathway depending on which structure the vessel is supplying
What are the main blood supplies we need to know and what do they supply
- Ophthalmic Artery ->Optic Nerve
- Middle Cerebral Artery ->Optic Tract
- Deep Branch of the Middle Cerebral Artery ->Optic Radiations
- Posterior Cerebral Artery -> V1 Striate Cortex
The middle cerebral artery is more likely to cause damage where? What about the posterior cerebral artery?
- middle: More likely to cause damage to peripheral visual field
- posterior: More likely to cause damage to central visual field
What is agnosias?
inability to identify something by sight
WHAT pathway
What is simultanagnosis
inability to perceive more than one object at a time
What is prosopagnosia
Inability to perceive faces (including your own)
Affects ventral pathway
What is akinetopsia?
motion blindness
What are these?
- Apperceptive agnosia –
- Associative agnosia -
- Semantic agnosia –
- Achromatopsia –
- Apperceptive agnosia – Inability to distinguish shapes
- Associative agnosia – inability to recognize what something is used for
- Semantic agnosia – inability to recognize signs and their symbolic meanings
- Achromatopsia – loss in color vision (V4 and V8)
What is alexia and what is usually paired with?
- inability to recognize words/read
- agraphia-> cannot write
What does congenital cataracts lead to?
leading to clouding of the lens
What does cataracts inhibit?
inhibits the ability of the lens to properly refract light onto the retina
With cataracts, the visual pathway is not damage, so what is the problem?
The visual pathway is not damaged. Instead, the intensity of the stimulus is affected causing decreases in contrast and brightness sensitivity
* Can also lose macula vision
- When do we have lots of plasticity in vision?
- What did they find out when looking fixing catarats in young children and teens?
- Younger, up to eight
- some of them did realy well but others not so much
- the older children did not change as much as younger children but their visual cortex was able to adapt closer to normal level
When you have a younger child that has a detect in one eye and wanting to fix it, what is VERY IMP? WHY?
You need to cover the unaffected eye because the eyes are competitive
* once one eye is damage, the other eye will take over that visual cortex
What is up with peripheral drift optical illusions?
- characterized by anomalous motion that can be observed in the peripheral vision
- d/t edge and motion sensitivity of receptor fields associated with eye mvt
