visual pathway

visual world

• everything you can see with one open eye

• temporal (lateral) part → projects to the nasal retina

• nasal (medial) part → projects to the temporal retina

binocular vision

area seen with both eyes at the same time

• gives us depth perception: ability to distinguish between near and far objects

central vision

• middle of the world

• looking at the someone’s nose

hemifield

• Left side = left hemifield

  • Point of light in left temporal hemifield → focused onto left nasal retina

  • Point of light in your left nasal hemifield → focused on the right temporal retina

• Right side = right hemifield

  • Point of light in right temporal hemifield → focused onto right nasal retina

  • Point of light in right nasal hemifield → focused on left temporal retina

thalamus

• left world processed by right brain

• right world processed by left brain

• optic nerve coming out of the retina

• optic tract goes into the thalamus

• optic chiasm allows info to cross

LGN

• nuclei of the thalamus that receives visual info from retina

• first region: two layers

• second region: four layers

• temporal retina: goes to layer 2, 3, 5

• nasal retina: goes to layer, 1, 4, 6

• ganglion cells

  • m-type = movement

  • p-type = color

cortex

• layer 4 receives info from the thalamus

  • has 3 layers: A, B, C

    • C contains alpha and beta

      • alpha: activated by info processed by M type ganglion cells

        • movement

        • layers 1,2 of LGN

      • beta: activated by info processed by P type ganglion cells

        • color

        • layers, 3, 4, 5, 6 of LGN

right temporal hemifield focuses on right nasal retina

• decussates using the optic chiasm → goes into the optic tract

• layers 1, 4, 6 of LGN

right nasal hemifield focuses on left temporal retina

• already crossed into left optic tract → so no need for decussation

• layers 2, 3, 5 of LGN

left temporal hemifield focuses on left nasal retina

• decussates using the optic chiasm and goes into the right optic tract

• layers 1, 4, 6 of LGN

left nasal hemifield focuses on right temporal retina

• already crossed into the right optic tract, so no need for decussation

• layers 2, 3, 5 of LGN