NEUR3112 Lecture Notes - Lecture 14: Optic Chiasm, Optic Tract, Optic Nerve
Document Summary
Visual system must construct a unified image from multiple facets. Retina provides a series of incomplete, ambiguous 2d snapshots that jump around. Higher visual centres must fill in the gaps, stabilise, generate a unified percept. Rats and mice have different visual systems -. Though a lot of studies are done on them. Axons from retinal ganglion cells form their first synapses in the brain stem & midbrain. Before doing this, they pass through 3 structures. Optic tract -> synapses with the midbrain structures. Left part of left visual hemifield is seen by left nasal retina (-> a) Seen in 2 different parts of 2 different eyes. Right part of left visual hemifield is seen by right temporal retina (-> b) Only axons from the nasal retina cross over (partial decussation) Hence: crossing of optic fibres at the chiasm means that the left visual hemifield is viewed" by the right hemisphere of the brain (and vice versa)
