Module D-07 Flashcards
half of the visual field for the eye that is towards the midline is called the
Nasal hemifield
half of the visual field for the eye that is away form the midline is called the
Temporal hemifield
degree of upward visual field
50 degrees ( eyebrows obstruct view)
degree of downward visual field
80 degrees
Describe how the visual field gets projected onto the retina
- The superior half of the visual field is projected to the inferior half of the retina, and vice versa.
- Nasal visual hemifield goes onto temporal retina and Temporal visual hemifield gis projected onto nasal retina
4 locations where the projections of the retinal ganglion cells synapse
1) Lateral geniculate nucleus (thalamus)
2) Suprachiasmatic nucleus (hypothalamus)
3) Pretectal nucleus (midbrain)
4) Superior colliculus (midbrain)
Which nucleus is relay station between the retina and the primary visual cortex?
Lateral geniculate nucleus
What is the purpose of the fibers of retinal ganglion cells that terminate in the suprachiasmatic nucleus?
trigger the circadian clock
What is the purpose of the fibers of retinal ganglion cells that terminate in the Pretectal nucleus?
part of the afferent limb of the pupillary light reflex
What is the purpose of the fibers of retinal ganglion cells that terminate in the Superior colliculus?
contribute to eye movements
What causes binocular vision?
the overlap of the visual fields of both eyes
________ retina fibers dont cross over
Temporal
Describe pathway of light seen in left superior quadrant of both eyes
1) Right eye: light is in nasal superior hemifield and projects
onto temporal inferior hemiretina
temporal fibers follow optic nerve=> optic
chiasm (no crossing over) => optic tract =>
synapse in right lateral geniculate nucleus =>
=> temporal radiation fibers of LGN => synapse
in inferior portion of Primary visual cortex
2) Left eye: light in temporal superior hemifield and projects
onto nasal inferior hemiretina
nasal fibers follow optic nerve=> optic
chiasm (CROSSOVER) => optic tract
(contralateral side)=> synapse in right lateral
geniculate nucleus => temporal radiationfibers
of LGN => synapse in inferior portion of Primary
visual cortex
Fibers of the LGN that carry info of superior visual field follow __________ radiation pathway and end up in _________ part of primary visual cortex
Temporal; Inferior (to calcarine sulcus)
Fibers of the LGN that carry info of inferior visual field follow __________ radiation pathway and end up in _________ part of primary visual cortex
Parietal; superior ( to calcarine sulcus)
Describe pathway of light seen in left inferior quadrant of both eyes
1) Right eye: light is in nasal inferior hemifield and projects
onto temporal superior hemiretina
temporal fibers follow optic nerve=> optic
chiasm (no crossing over) => optic tract =>
synapse in right lateral geniculate nucleus =>
=> parietal radiation fibers of LGN => synapse
in superior portion of Primary visual cortex
2) Left eye: light in temporal inferior hemifield and projects
onto nasal superior hemiretina nasal fibers
follow optic nerve=> optic chiasm
(CROSSOVER)
=> optic tract (contralateral side)=> synapse in
right lateral geniculate nucleus => parietal
radiation fibers of LGN => synapse in superior
portion of Primary visual cortex
Brodmann’s area for primary visual cortex
Area 17 , around the occipital pole mainly on medial side of the brain
Blood supply of primary visual cortex
- major blood supply from calcarine branches originating from the posterior cerebral artery.
- small portion of the primary visual cortex located around the occipital pole, may also receive blood supply from the middle cerebral artery (especially after an occlusion of the
posterior cerebral artery).
The topographical organization of the primary visual cortex is called “_________” map
retinotopic
Where on the primary visual cortex would the macular region of vision be located?
closer to the occipital pole
Where on the primary visual cortex would the peripheral region of vision be located?
closer to parieto-occipital sulcus
What are the two types of columns in Primary visual cortex?
1) Ocular Dominance Columns
2) Orientation Columns
What are ocular dominance columns?
areas (columns) dedicated to input from one eye, for example the ipsilateral eye (I), which lie next to areas (columns) dedicated to input from the contralateral eye (C).
What are Orientation columns?
Columns dedicated to orientation preference of the light source
How are the ocular dominance and orientation columns actually placed?
Neurons within the primary visual cortex are characterized by their preference for input from either the ipsilateral or contralateral eye, as well as by their preference for a certain orientation of a bar of light.
What are parallel pathways of the retina?
parallel pathways which follow the same anatomical
structures are specialized for certain aspects of visual
information, which are depth, motion, form and color.
The pathway for depth and motion starts with
____________ in the retina.
magnocellular neurons (M ganglion cells)
Describe the pathway for Magnocellular neurons
synapse in 2 of the 6 layers of the LGN, then to the primary visual cortex and then follow the parietal (dorsal) pathway
The pathway for form and color starts with __________ in the retina
parvocellular neurons (P ganglion cells)
Describe the pathway for Parvocellular neurons
Synapse in the other 4 of the 6 layers of the LGN , then to the primary visual cortex and then follow the inferior temporal (ventral ) Pathway
If there is a lesion in the Optic nerve then the visual field defect is _________ and the lesion origin is ___________
Monocular blindness; Optic neuritis
If there is a lesion in the Optic chiasm then the visual field defect is _________ and the lesion origin is ___________
Bitemporal hemianopia; Pituitary tumor
If there is a lesion in the Optic tract then the visual field defect is _________ and the lesion origin is ___________
Homonymous hemianopia; Temporal lobe tumor
If there is a lesion in the temporal radiation( Meyer’s loop) then the visual field defect is _________ and the lesion origin is ___________
Homonymous superior quadrantic anopia; Temporal, or
occipital lobe tumor
If there is a lesion in the Parietal radiation then the visual field defect is _________ and the lesion origin is ___________
Homonymous inferior quadrantic anopia ; Parietal, or occipital lobe tumor
If there is a lesion in the visual cortex then the visual field defect is _________ and the lesion origin is ___________
Homonymous hemianopia; Posterior cerebral artery dysfunction
What type of lesions allow for macular sparing ?
vascular lesions involving the posterior cerebral artery or its branches
Why does macular sparing occur?
the blood supply of the occipital pole of the cerebral cortex, which is the area representing macular vision, may
stay intact, due to sufficient blood flow originating from the middle cerebral artery
Color agnosia aka
Achromtopsia aka cortical color blindness
What is Achromatopsia?
Inability to distinguish colors or color hues
What causes Achromtopsia?
cortical lesions in areas 18 or 37
