Central pathway: vision Flashcards
Unilateral optic nerve lesion
a. blindness in affected eye only
b. location: in optic tract
a. blindness in affected eye only
b. location: in optic tract
Unilateral optic nerve lesion
Lesion of optic chiasm
a. bitemporal hemianopia; interupts fibs from nasal portions of retina
b. horse with blinders—loss of peripheral vision
a. bitemporal hemianopia; interupts fibs from nasal portions of retina
b. horse with blinders—loss of peripheral vision
lesion of optic chaism
Unilateral optic tract lesion
a. get __________hemianopia (same side/half/vision impairment)
contralateral homonymous
Location of unilateral optic tract lesion is:
Location is optic tract post chaism
Fibers interrupted on a unilateral optic tract lesion
c. interrups fibs from temporal parts of retina on the ipsilateral side and the nasal protion of the opp side
Unilateral optic tract lesion of left side affects which side/visual field
get right side of both field affected
Unilateral lesion of optic radiation in anterior temopral lobe (meyers loop)
End up with contralateral upper quadrantanopia—bc fibers wind around inferior horn of lateral ventricle in temporal lobe
End up with contralateral upper quadrantanopia—bc fibers wind around inferior horn of lateral ventricle in temporal lobe
Unilateral lesion of optic radiotionin anterior temporal lobe (meyers loop)
Unilateral lesion in medial part of optic radiation in parietal lobe
contralateral lower quadrantanopia
b. affected fibers course superior and usually lesion is in parietal lobe
c. if on left side, you loose LR quadrant of both eyes
Unilateral lesion in medial part of optic radiation in parietal lobe
causes homonymous hemianopia
occipital lobe lesion
B/c optic radiations fan out widely b4 entering visual cortex, lesions of occipital lobe often will
spare foveal vision
Most common cause of occipital lobe lesion
intracerebral hemorrhage
Lesion of cortical area of occipital pole represent
macula thus we get homonymous hemianopic central scotoma
Direct pupillary light reflex
response in the stimulated eye
Consensual reflex
response in unstimulated eye
Lesion on optic tract of one side (right eye)–shine light in right eye, you will __________
–shine light in left eye, you will _________
not get direct or consensual constriction
get both direct and consensual constriction
Lesion on right Ed/Wes
- -shine light on right eye, signal goes to both Ed/Wes nuclei-
- since right Ed knocked out, no direct constriction but will get consensual constrction
Lesion of pretectal area of right side
–Get both direct and conensual:
keep in mind fibers cross at optic chiasm so you will trigger the left path and right path. Once we get to pretectal area, they project contra/ipsi to the Ed/Wess so even if the right pretectal cant stimulate the right Ed, the left pretectal will
Suprachiasmitic nucleus is good for
circadian clock and melatonin production
This keeps track of fast moving objects in periperphy and helps you reponsd quickly
Superior colliculus
This is key for spatial neglect, only attend to or pay attention to one side
pulvinar of thalamus
Pathway: light enters on retina→ will go through _______and tract (follows same pattern as vision)
→ BYPASSES the_____ and instead synapses on the______ area in the midbrain.
→ fibers go contralatreal and ipsilateral to the _______
→ from Ed/Wes nuclei sends out pregang____ fibers that exit the midbrain , hop on the_____ nerve and stay contralateral til they synpase on ______
→ from ciliary gang, post-syn PNS head to the pupillary sphincter via the _______
optic nerve (CN II) LGN Pretectal Ed/Wes nuclei PNS oculomotor ciliary gang short ciliary nerves
recieves input from parasol cells, key for quick movemnt
Superior colliculus
The superior colliculus has output to
tectospinal tract for head/trunk mvmt
What maintains division between neurons/circuits that carry motion-related signals and those that carry color/form and content
maintained from retina through LGN via striate cortex
Striate cortex is then _______ on retinotipoc representation and are mapped
superimposed
Area 17
Primary visual cortex
Area 18 and 19 are
extra striate cortex
V5 is also called
middle temporal (MT)
Striate cortex is
V1
RFs are smallest in
V1 then get larger
Further you get from V1, the precision is
poor
Damage to V4 results in
impairement for color discrimination tasks
Damage to V4/5 is associated with impairment in:
dectection of motion
Bilateral damage to human homologue V4 produces
global impairement of color perception
Bilateral damage to MT produces sudden global impairement in
ability to detect motion: freeze frame disease
freeze frame lesion
cerebral akinetopsia, bilateral lesion at MT
Lesion of extrastriate areas have segregated function thus outputs from V1 are
also segregated
In V1 we see anatomical segregation based on:
color, form and motion
inability to recognize a face is damage to
V4
V1 projects heavily into
V2
Lesion here impair allocation of attention or attentional neglect
pareital lobe lesion
lesion here impair recogntion (based on size, color, texture)
temporal lobe lesion
V1–> V2–>MT is the
dorsal pathway leading to parietal lobe
V1–>V2–> V4 is the
ventral pathway leading to temporal lobe
furtherst downstream from V4 and receptive fields are huge
Inferotemporal complex
damage to part of fusiform gyrus produces
selective impairment in recognition of faces
visuospatial neglect is due to damage to
parietal cortex
ventral stream heads to
temporal lobe
dorstal stream heads to
parietal lobe
High level brain structures that recieve input on
memory
intention
emotion
hippocampus
prefrontal cortex
limibic system
Broadman area 18-19 account for at least _____ areas with their own map of visual space
9
Ventral stream: Face area is in:
IT cortex