The Visual Pathway

1
The Visual Pathway
"I have such poor vision I can date anybody."
-Garry Shandling
2
Introduction..

• The function of the visual pathway is to conduct
  signals from the retina to the occipital lobe.
• Due to the pattern of signal conduction, each
  half of the visual field of either eye is mapped
  to the contralateral cerebral hemisphere.

3
Signal Initiation

• Light, striking the phototransducer cells, leads
  to activation of retinal ganglion cells.
• Ganglion cell axons converge to form the Optic
  Nerve (CN II).

4
Where do we go from here?

• A partial decussation of the optic nerve occurs
  at the optic chiasm
• The optic tract conducts information from the
  chiasm to the lateral geniculate body.

5
The Lateral Geniculate Body

• The LGB is divided into six layers.
• 1, 4, and 6 receive crossed fibers
• 2, 3, and 5 receive uncrossed fibers

6
Where to now?

• Fibers from the Lateral Geniculate Body curve
  around the lateral ventricle in the internal
  capsule.
• These axons travel in the optic radiations and
  terminate in the cortex adjacent to the calcarine
  sulcus
• The retinotopic pattern is flipped both
  horizontally and vertically in the cortex.

7
Flipped?
8
The Big Picture
9
Damage to the Visual System
(Ventral View)