Visual Pathway - Lecture 8 Flashcards
what is the visual pathway
amount you can see w/o head or eye movement
retina is considered
in quarters (quadrants)
what do the retinal elements in any quadrant represent
visual field that is opposite to it in the physical world
central visual pathways
optic nerve and tract
lateral geniculate nucleus
superior collicus
accessory optic tract
optic nerve and tract
axons of retinal ganglion cells collect to form a tract know as the optic nerve
optic chiasm
crossing point
point at which some fibers from each side of the visual field decussate
what does each optic tract carry
signals from one half of the visual field
left optic tract carries
visual info from the right visual field of both eyes
how do visual afferents continue
as the optic tract
lateral geniculate nucleus
largest area of the 3 areas that the optic tract projects to
where is LGN
caudal and lateral to thalamus
LGN has
6 layers
6 layers of LGN
3 for the ipsilateral eye
3 for the contralateral eye
what do neurons from LGN project
to the primary visual cortex (area 17) of the occipital lobe
superior collicus
optic tract sends a smaller projection to the superior collicus
where do fibers go from superior collicus
sent to contralateral side and other areas of the brain
where does info from the superior collicus help generate
appropriate eye movement
how are receptive field of the superior collicus
large for movements that are unidirectional horizontal movements from the central to the peripheral fields
accessory optic tract
some fibers seperate from the optic tract
project to optic nuclei, vestibular nuclei and the pons
where do fibers go from the pons –> accessory optic tract
projections ascend to the cerebellar flocculus
helps to control eye movement
cortical projections
pathways from LGN to the visual cortex
project as the optic radiations to area 17 in the occipital lobe
where to optic radiations travel
posteriorly through Wernike’s area in the temporal lobe
what can lesion to cortical projection cause
speech and visual field deficits
where is the visual cortex
deep w/in occiput
gets info from LGN
visual cortex is areas
17-19
occipital lobe boundaries
difficult to define
many variations
area 17 receives
projections from other areas
what is considered the major gateway for visual info from the cortex
area 17
how many layers does the visual cortex have
8
how is area 17 arranged
topographically
mapping the visual field of the retina
receptive fields
retinal cells and their related pathways
sensitive to specific stimuli in specific patterns
what can receptive fields be responsive to
concentric circles
left to right
right to left
center to periphery
light to dark
visual cortex is the first opportunity
for true binocular info representation
binocular cells
respond when the corresponding spatial areas of the eye receptive fields are stimulated
what does evidence indicate –> visual cortex
early visual experience can alter the development of binocularity cells
