Visual processing from the retina to the brain
RGCs send axons through the optic nerve
There can be no photoreceptors where the nerve starts
This is why we have a blind spot in our field of view
How is each retina divided
Into nasal hemiretina and temporal hemiretina
Their projections diverge at the optic chiasm
Nasal hemiretinas cross over
Result: the left visual field is represented in the right hemisphere and vice versa
Lateral Geniculate Nucleus (LGN)
RGC axons reach the LGN of the thalamus LGN has 6 layers: Layers 1-2: Magnocellullar (big cells) -Motion and dim light sensitive from rods Layers 3-6: Parvocellular (small cells) -Color and detail resolution from cones
LGN receptive fields
Center-surround like retinal ganglion cells
Bigger receptive fields than RGCs
-See a larger chunk of visual space
From the LGN to the cortex
Axons from LGN travel through the optic radiations to the Primary Visual Cortex (V1)
Maintains retinotopic organization:
1. Each V1 neuron responds to a stimulus in a small area in the field of view, and
2. Neighboring V1 neurons respond to stimuli in nearby locations in the visual field
