Systems Physiology II 6010

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Systems Physiology II 6010
Lecture 9 Sensory system Vision
Bradley Greger, PhD
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Anatomy of the Eye

• Cornea
• Sclera
• Anterior Chamber
• Aqueous humor
• Iris
• Lens
• Ciliary muscle
• Posterior Chamber
• Vitreous humor
• Retina
• Fovea
• Optic disk

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The Retina

• Cones
• High luminance
• Color vision
• Rods
• Low luminance
• No action potentials

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Light Transduction

• Retinal
• 11-cis-retinal
• All-trans-retinal
• Separates from Opsins
• Decreases Na permeability
• Rhodopsin
• Rods cells
• Cone Opsin
• Cone cells
• Associated with three pigments

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Light Transduction

• Rhodopsin
• No color information
• Cone Opsin
• Blue
• Green
• Red

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The Retina

• Photoreceptors
• Rods
• Cones
• Vertical connections
• Bipolar cells
• Horizontal connections
• Horizontal cells
• Amacrine cells
• Output
• Ganglion cells
• First action potentials

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On-Center Off-Center Activation

• Photoreceptors
• Single neurotransmitter
• Continuously released in darkness
• Decreased release in light
• Bipolar cells
• Off-cells
• Excited by neurotransmitter
• Hyperpolarized by light
• On-cells depolarized
• Inhibited by neurotransmitter
• Depolarized by light

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Center Surround Antagonism

• Inhibitory interneuron horizontal cell

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Distribution of Photoreceptors

• Cone photoreceptors in human

• Relative densities of Rods Cones

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Many types of amacrine cells

• Many different types of amacrine cell
  morphologies
• Process in different layers
• Process of different complexities

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Many types of amacrine cells

• Many different types of amacrine cell
  morphologies
• Process in different layers
• Process of different complexities
• Process with different spatial extension
• Different types of image filters?

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Two major classes of ganglion cells

• Midget cells have small dendritic fields, reach a
  high density in the central retina, and make up
  the great majority of ganglion cells.
• Parasol cells have much larger dendritic fields
  and a lower spatial density.
• The midget and parasol cells project,
  respectively, to the parvocellular and
  magnocellular layers of the dorsal lateral
  geniculate nucleus

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Two major classes of ganglion cells

• Dendritic field changes with eccentricity
• Integrating information over larger region of
  space, lower acuity with eccentricity

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Retina to Lateral Geniculate Nucleus

• Optic nerves
• Prior to chiasm
• Optic tract
• After chiasm
• Optic chiasm
• Eye to hemi-field

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Lateral Geniculate Nucleus

• Ipsilateral and contralateral input in layers
• Magnocellular (big cell) Parvocellular (little
  cell) layers

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Optic Radiations

• Hemi-field information to primary visual cortex

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Primary Visual Cortex

• Image inverted
• Foveal expansion
• More cortex devoted to foveal information
• Correlates with cone density
• Mostly deep in sagital fissure

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Response Field Circuits

• Multiple LGN cells project onto one cortical cell
• Topographically arranged inputs generate
  orientation selectivity

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Cortical Columns

• Process specific types of information
• Ocular dominance
• Each eye
• Orientation selective
• Orientation processing
• Blobs
• Color processing

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Higher visual processing

• What
• Ventral pathway
• Where
• Dorsal pathway

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Higher visual processing

• It gets somewhat complicated

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Color vision

• What happens to color vision if filter out
  everything but only one wavelength of light
• You would only see that color right?

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Color vision
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Color vision
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Color vision
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Color vision
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Color
http//www.psychologie.tu-dresden.de/i1/kaw/divers
es20Material/www.illusionworks.com/html/color_aft
ereffect.html
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Motion
http//www.bu.edu/smec/lite/perception/waterfall/
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Lots more information at

• http//webvision.med.utah.edu/