Lecture 21 Vision II Lateral Geniculate and Visual Cortex

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Vision II November 12, 2007
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Fig 26-10
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Fig 26-9
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Fig 26-7
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Hermann Grid
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Fig 26-1
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Parallel Processing of Visual Information Magno
cellular pathway and Parvocellular Pathway
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Classification of primate retinal ganglion cells
1. Receptive fields a) circular, on-center /
off-surround b) circular, off-center /
on-surround
2. Magnocellular pathway (M) a) larger receptive
fields b) little or no sensitivity to color c)
greater sensitivity to small differences in
contrast d) greater sensitivity to movement e)
fire at higher frequencies are
faster-conducting
3. Parvocellular pathway (P) a) small
receptive-field centers b) high spatial
resolution c) sensitive to color d) convey
information about fine detail at high
contrast e) analysis of form (parvocellular-inte
rblob system)
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Figure 24-3
Human cone photopigments compared with rod
rhodopsin


rod rhodopsin
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Fig 29-1
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Receptive-field organization of color-responsive
parvocellular neurons in monkeys
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Different Types of Color Vision Dichromatic
vision Trichromatic Vision Tetrachromatic Vision
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Figure 21-10
Parallel pathways of the visual system
Extrastriate cortex (32 areas)
Lateral Geniculate body
Striate cortex
Retina
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Projections from retina to visual areas of
thalamus (LGN), midbrain (pretectum superior
colliculus), and primary visual cortex
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Projections from retina to visual areas of
thalamus (LGN), midbrain (pretectum superior
colliculus), and primary visual cortex
visual information for perception
pupillary reflexes
eye movements
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Fig 27-5
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In-Class Exercise
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Fig 27-1
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Fig 27-6
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Fig 27-7
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Maps of the visual field in the LGN
Receptive fields are highly ordered in each LGN
layer
neighboring regions of retina connect with
neighboring LGN neurons
therefore receptive fields of adjacent neurons
overlap extensively
Higher-acuity region of retina (fovea of primate,
area centralis of cat), with small receptive
field centers, projects to the greater portion of
each LGN layer
area of LGN to which a region of retina maps
reflects its density of photoreceptors
relatively few LGN cells are devoted to
peripheral retina
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David Hubel Torsten Wiesel
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David Hubel Torsten Wiesel
characterizing receptive fields of LGN neurons in
cats first type
on-center cell
http//www.physiology.wisc.edu/yin/public/
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David Hubel Torsten Wiesel
characterizing receptive fields of LGN neurons in
cats second type
off-center cell
http//www.physiology.wisc.edu/yin/public/
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Receptive fields of neurons in cat LGN
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Fig 27-9
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Kandel fig. 23-7
Layers and cells of primary visual cortex V1
Konio- cellular (inter- laminar) color
magno- cellular
local inter- neuron inhibitory (GABA)
projection neurons (to other cortical deep
brain areas) excitatory (glutamate)
local inter- neuron excitatory (glutamate)
parvo- cellular