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Occipital Lobe

Occipital Lobe. Videos: Brain modules 8,9,10, 11 Consciousness- Blindsight. EYE. Receptors: rods and cones. Rods Cones. 120 million periphery sensitivity night vision. 8 million central acuity color vision. Anatomical Pathway in the Retina.

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Occipital Lobe

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  1. Occipital Lobe • Videos: • Brain modules 8,9,10, 11 • Consciousness- Blindsight

  2. EYE

  3. Receptors: rods and cones Rods Cones • 120 million • periphery • sensitivity • night vision • 8 million • central • acuity • color vision

  4. Anatomical Pathway in the Retina

  5. Retina

  6. Optic Nerve Exits

  7. Locating Blindspot

  8. Stare at single star for 60-90 sec

  9. Color-Deficient Vision • People who suffer red-green blindness have trouble perceiving the number within the design

  10. 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” Occipital Lobe

  11. The Lateral Geniculate Nucleus of Thalamus

  12. Central Visual Pathways: the Visual Cortex • Visual Cortex • Cortical magnification factor -- foveally weighted: cortical volume is related to retinal area’s spatial resolution • -- central 10 degrees of VF around fovea maps to 80% of V1 (primary visual cortex)

  13. Simple Cells • orientation selective • Response to spots • On - Off regions • Responds to edges - - - - - - + + + • Complex Cells • movement sensitive • can’t predict response from • static on off receptive fields Receptive Field Properties of Cortical Neurons Based on Hubel and Wiesel

  14. Hypercomplex Cells • end stopping

  15. Form Perception • LGN - Parvocellular System • V1 (Interblobs) ---> V2 ---> V3 • Inferotemporal Cortex (MT) • complex stimuli - grandmother cells • Damage leads to visual agnosia

  16. Movement Perception • Rods • LGN - Magnocellular system • V1 ---> V2 ---> V5 • V5: middle temporal lobe (MT) • Damage - akinetopsia (unable perceive motion)

  17. 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 ~ High-level Visual Processing

  18. 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?

  19. 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

  20. V2 – three categories • Pale stripes • Wavelength sensitivity • Orientation sensitivity • Disparity sensitivity • Thin stripes • Wavelength sensitivity • Thick stripes • Motion sensitivity • Orientation sensitivity • Disparity sensitivity

  21. V4 – recordings (Color) Stimuli –light patches of different wavelengths Neural response

  22. MT – recordings (Form) stimuli Neural response

  23. eyetracking

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