This is part of the summary of Course 2.4 Perception at Erasmus University Rotterdam. I put a lot of effort into making these summaries and included pictures and graphs to make things as understandable as possible. I managed to get quite a high grade on the course exam at the end (8.8). Note though...
Signals from the retina to the cortex:
The visual system:
- Retina → optic nerve → Lateral geniculate nucleus (LGN) in the thalamus → Occipital lobe (primary visual
receiving area = striate) → temporal lobe/ parietal lobe/ frontal lobe
- Superior colliculus: involved in controlling eye movements
- Signals from each half of retina cross over to opposite side of the brain
Visula Maps:
- Visual field divided up into 4 quadrands (upper, lower, nasal, temporal)
- Upper visual field projects onto lower retinal surface
- Nasal visual field projects to temporal retinal surface
- Tectopulvinar system (evolutionalry old , shared with many animals)
o No longer dominant in humans
- Geniculostriate system (begins in the same way as tectopulvinar system)
- Optic nerves cross at optic chiasm
o Outside halves of each retina stays on the same side
o Other half crosses to the other side
- Beyond optic chiasm optic nerve is called optic tract
Tectopulvinar System: optic nerve→ brain stem/midbrain →superior collicli → pulvinar → cortex
- branches to brain stem and midbrain
- in animals brain stem = tectum; more primitve visual center compared to cortex
- superior collicli = upper 2 bumps (out of 4) that recives incoming fibers
- most cells are magno type → rapid response to light changes; not sensitive to details, but location and motion
- deeper layers even tactile and auditory stimuli
- input from retina, primary visual cortex, motion processing cortex
- then to pulvinar (lateral posterior nuclei) and later cortex (V2)
Geniculostriate System: Lateral Geniculate Nucleus (LGN)
- Regulates neural information coming from the retina
- Receptive fields of LGN neurons: Center-surround configuration
- Information flow:
o 90% of optic nerves arrive at LGN
o Receives signals from thalamus, cortex, brainstem, other neurons in LGN → output to cortex
o More input from cortex than retina, not much output from LGN to cortex
o Organizes information (dependent on environmental information, receptors that generated
info, left/right eye)
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