The optic n and retina are an outgrowth of what part of the brain
Prosencephalon
Light passes from objects in visual field, through pupil to subtend an image upon the retina, which creates
Retinal field
Focusing on an object causes it to be centered where
Fovea centralis and macula lutea
*Visual fields are divided into what zones
Binocular (overlapping zones of eyes) Monocular (seen by one eye)
The monocular zones make up
Peripheral vision
Retinal fields are
Location on the retina that an object in the visual field is projected
*What are retinal hemispheres
Nasal and temporal halves of the retinal fields
*The image formed on the retina is inverted in what directions
Lateral and vertical dimensions
*The left half of the visual field is made of
Nasal half of the left retina and temporal half of the right retina
*The right half of the visual field is made of
Nasal half of the right retina and the temporal half of the retina
*Where does CN 2 decussate
Optic chiasm
*The nasal half of the each retina goes where
Contralateral optic tract
*The temporal half of each retina goes where
Ipsilateral optic tract
*The optic tract of each side consists of
Temporal retina fibers of ipsilateral fibers Nasal retina fibers of contralateral fibers
*The optic tract curves posteriorly around the cerebral peduncle and terminates in the
Lateral geniculate nucleus
*The ventral base of the LGN is formed by
Optic tract (retinogeniculate) fibers
The dorsal and lateral borders of the LGN and optic tract are formed by
Optic radiations
*The LGN is divided into what cellular layers
Magnocellular and parvocellular
*The magnocellular layer is made of
Layers 1 and 2 (ventral)
The magnocellular layer receives input from
Rods
The magnocellular layer has a _______ receptive field and is sensitive to ___________
Large; moving stimuli There are also faster conducting neurons here
*The parvocellular layer is made of what layers
3-6
The parvocellular layers receive input from
Cones
The parvocellular layer has a _________ receptive field and is sensitive to _________________
Small; high acuity color Slower axons than magnocellular and tonically active with stationary objects
*The temporal retina remain uncrossed and terminate in layers ________ of the ipsilateral LGN
2, 3, 5
*Nasal retina cross to contralateral side and terminate in layers _________
1, 4, 6 of contralateral LGN
*The R nasal retina synapses where
Left LGN layers 1, 4, 6
*The L temporal retina synapses where
Left LGN layers 2, 3, 5
*The L nasal field synapses where
Right LGN layers 1, 4, 6
*The R temporal retina synapses where
Layers 2, 3, 5 of the right LGN
*Secondary neurons from the LGN extend a large bundle of myelinated fibers called the
Optic radiation
*where do the optic radiations synapse
Visual cortex (striate cortex) on the upper and lower banks of the calcarine sulcus
*Fibers from the lower quadrant of the contralateral hemifields target what
Superior bank of the calcarine sulcus on the cuneus
*Fibers from the upper quadrant of the contralateral hemifields target what
Inferior bank of the calcarine sulcus on the lingual gyrus
Where do fibers from the lower quadrant of the contralateral hemifield originate
Dorsomedial portion of LGN and then arch caudally to pass through the retrolenticular limb of the internal capsule
*Where do the fibers from the upper quadrant of the contralateral hemifields orginate
Ventrolateral portion of LGN and then arch rostrally, passing into the white matter of the temporal lobe to form the meyer loop
*Damage to the temporal lobe can cause what visual deficit
Superior visual field deficit d/t Meyer’s lobe passing here
Inferior visual fields project to the cortex above ________ ________ and superior fields project to the cortex below _________ ________
Calcarine sulcus
*What is group together as the visual association cortex
Areas 18, 19, and parts of the temporal and parietal lobe
The superior colliculus does what
Spatially directs head movements and visual reflexes
What inputs does the superior colliculus receive
Retinal input and cortical input
The pretectal area is important in what general task
Discerning light intensity which is involved in the pupillary light reflex
Corticotectal fibers descend to the superior colliculus and control
LMN of CN 3, 4, 6 Requires consciousness to test these
Hemianopsia is
Blindness in one half of the visual field
Quadrananopia is
Blindness in a quadrant of visual field
Homonymous visual fields are
Conditions in which visual field losses are similar in both eyes
Heteronymous visual fields are
Conditions in which the two eyes have non-overlapping field losses
Congruous deficits are
a similar loss of visual field in each eye (i.e same quadrant); suggests damage closer to occipital lobe
Incongruous deficits are
Not symetrical
Damage anterior to chiasm
Only affects ipsilateral eye
Damage at the chiasm
Causes heteronymous deficits
Damage behind chiasm causes
Homonymous defects
Associative visual agnosia is caused by
Infarction of the left occipital lobe and posterior corpus callosum
What is associative visual agnosia typically secondary to
Posterior cerebral A occlusion
What does associative visual agnosia do
Disconnects the language area from the visual association cortex
What are the symptoms of associative visual agnosia
Patient cannot name or describe an object in the visual field but can recognize and demonstrate its use
What is formed with a lesion at A
What is formed with a lesion at B
What is formed with a lesion at C
What happens with a lesion at D
What happens with a lesion at E
What happens with a lesion at F
What happens with a lesion at G
What happens with a lesion a H
What happens with a lesion at I
What happens with a lesion at J
What happens with a lesion at K
