Occipital Lobe

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Occipital Lobe

• Videos
• Brain modules 8,9,10, 11
• Consciousness- Blindsight

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EYE
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Receptors rods and cones
Rods
Cones

• 120 million
• periphery
• sensitivity
• night vision

• 8 million
• central
• acuity
• color vision

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Anatomical Pathway in the Retina
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Retina
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Optic Nerve Exits
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Locating Blindspot
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Stare at single star for 60-90 sec
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Color-Deficient Vision

• People who suffer red-green blindness have
  trouble perceiving the number within the design

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Occipital Lobe

• axons of retinal ganglion cells
• 106 axons of retinal ganglion cells from each eye
  converge at optic chiasm and hemidecussate

• Retinal Ganglion Cells project to
• 20 project to the Superior Colliculus
  (retinotectal/pulvinar pathway) where it is
• 80 of the axons of retinal ganglion cells
  project to the Lateral Geniculate Nucleus
  (retinocortical pathway) what it is

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The Lateral Geniculate Nucleus of Thalamus
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Central Visual Pathways the Visual Cortex

• Visual Cortex
• Cortical magnification factor -- foveally
  weighted cortical volume is related to retinal
  areas spatial resolution
• -- central 10 degrees of VF around fovea maps to
  80 of V1 (primary visual cortex)

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Receptive Field Properties of Cortical
Neurons Based on Hubel and Wiesel
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Form Perception

• LGN - Parvocellular System
• V1 (Interblobs) ---gt V2 ---gt V3
• Inferotemporal Cortex (MT)
• complex stimuli - grandmother cells
• Damage leads to visual agnosia

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Movement Perception

• Rods
• LGN - Magnocellular system
• V1 ---gt V2 ---gt V5
• V5 middle temporal lobe (MT)
• Damage - akinetopsia (unable perceive motion)

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High-level Visual Processing

• V1- elementary properties detected (edge,etc)
• V2 -input from V1
• divergence of color, form, location
• V3 - shape (form) - inferotemporal
• V4 - color - lingual fusiform gyri
• V5 - motion - midtemporal
• PPC - location - posterior parietal cortex

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Striate Cortex (V1)

• Many more dimensions in which receptive fields
  may be described or tuning
• Receptive field size
• Sensitivity to motion?
• Sensitivity to chages in wavelength?
• Orientation selectivity?
• Occular dominance?

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Striate Cortex (V1)

• Projection to V1 from magnocellular portion of V1
  
• Motion sensitivity (direction and velocity)
• Orientation sensitivity
• Disparity sensitivity
• Projection to V1 from parvocellular portion of V1
  
• Wavelength sensitivity
• Orientation sensitivity
• Disparity sensitivity

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V2 three categories

• Pale stripes
• Wavelength sensitivity
• Orientation sensitivity
• Disparity sensitivity
• Thin stripes
• Wavelength sensitivity
• Thick stripes
• Motion sensitivity
• Orientation sensitivity
• Disparity sensitivity

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V4 recordings (Color)
Stimuli light patches of different wavelengths
Neural response
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MT recordings (Form)
stimuli
Neural response
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eyetracking
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