PHY2011 Lecture 23: Week 9 L1 (T4BL3) -processing Visual Sensations in the CNS
20 Jun 2018
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Week 9 L1 -processing Visual Sensations in the CNS
Segregation of different types of visual information at the retina
oTwo pathways of retinal ganglion cells carrying information
M-pathway (10% of cells are M-cells)
P-pathway (90% of cells are P-cells)
oRF properties
M-cell
- Large cells, long dendrites
- reach many photoreceptors
- large receptor fields
P-cell
- small cells, short dendrites
- reach few photoreceptors
- small receptor fields = fine detail
oλ of light
M-cells: just respond to light
P-cells: respond to diff λ of light
- But some aren’t λ sensitive
oTell us how much light in the centre and how much in the
surrounds
- Those that are λ sensitive get information from the cones
oTelling us about colour – how much of each λ in centre vs
surrounds
oAdaptation properties
M-cells: rapidly adapting cells
- Tells us about change and motion
P-cell: slowly adapting cells
- Can tell us fine detail about signal spacing
Characteristic M-cell P-cell
Number 10% 80%
RF size Large Small
RF λ selectivity No Yes
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Document Summary
Week 9 l1 -processing visual sensations in the cns. Segregation of different types of visual information at the retina: two pathways of retinal ganglion cells carrying information. P-pathway (90% of cells are p-cells: rf properties. P-cell: of light small cells, short dendrites. But some aren"t sensitive: tell us how much light in the centre and how much in the surrounds. Those that are sensitive get information from the cones: telling us about colour how much of each in centre vs surrounds, adaptation properties. Can tell us fine detail about signal spacing. The where and where to pathway: p-cells. The what pathway: information from the retina goes directly to the thalamus, lgn- part of thalamus that receives visual input, if eye is divided into two parts at the blind spot: Outer part goes to thalamus on the same side. Inner part goes to thalamus on the opposite side. Optic chiasm: where optic nerve fibres cross over.
