4. Vision - LGN to V1 Flashcards
involves the lateral geniculate nucleus of the thalamus which projects up to the visual cortex
the geniculo-striate pathway (aka thalamocortical pathway)
found in the occipital lobe and lies along the central sulcus
visual cortex
does the lateral geniculate nucleus (LGN) project contralaterally or ipsolaterally to the visual cortex?
ipsolaterally
why is the visual cortex also called the striate cortex?
because of its striped appearance
what happens at the optic chiasm?
axons from retinal ganglion cells on the nasal hemiretina cross over to the contralateral side of the brain
axons of the retinal ganglion cells leave the eye as the:
optic nerve
axons from the temporal hemiretina project to:
the lateral geniculate nucleus (LGN) on the ipsolateral side of the brain
what percent of visual information “crosses over” to the contralateral hemisphere at the optic chiasm?
~55%
due to the “crossing over” of visual information in the optic chiasm, the left visual field is represented in the:
right lateral geniculate nucleus (LGN) and the right visual vortex (and vice versa for the right visual field)
is there more or less decussation (crossing over) in lateral eyed animals?
more (have much less binocular overlap than frontal eyed animals)
how many layers are in the lateral geniculate nucleus (LGN)?
six
layers one and two of the LGN are known as the:
magnocellular layers
layers two, three, and five of the LGN receive input from the:
ipsolateral eye
layers one, four and six of the LGN receive input from the:
contralateral eye
layers three, four, five, and six of the LGN are known as the:
parvocellular layers
what are the light bands between the layers of the LGN?
konicellular layers
adjacent points in the visual field are represented by:
adjacent neurons in the LGN
what type of receptive fields are found in the lateral geniculate nucleus (LGN)?
centre-surround receptive fields (same as RGCs)
true or false: the parvocellular and magnocellular layers of the LGN receive inputs from different types of RGCs
true
the parvocellular layers of the LGN receive inputs from:
“midget” RGCs
the magnocellular layers of the LGN receive inputs from:
“parasol” RGCs
true or false: like RGCs and the LGN, visual cortical cells also have centre-surround receptive fields
false!
what are the three major cell types of the visual cortex?
- simple cells
- complex cells
- end-stopped cells
cells which responds to “bars” of light of a particular orientation (orientation selective)
simple cells
cells which respond to “bars” of light of a particular orientation, moving in a particular direction (direction selective)
complex cells
cells which respond to moving “bars” of light of a particular orientation and a particular length (others like moving “corners”)
end-stopped cells
go review slide 299
there is just no good way to write that down
the cells of the visual cortex are known as:
“edge detectors” (in a scene, we identify where the edges are before anything else)
how did Hubel and Wiesel build a simple cell receptive field from surround-centre receptive fields of LGN neurons?
receptive fields of LGN neurons overlap with one another and the summation of them creates an oval shape with a “bar” in the centre
how did Hubel and Wiesel build a complex cell receptive field?
summation of the inputs from simple cells
how did Hubel and Wiesel build an end-stopped cell receptive field from receptive fields of complex cells?
adjacent complex cells can be excitatory or inhibitory, and the summation of these inputs will either excite or inhibit the neuron
go review slide 304
this one is good i promise
how many layers are in the visual cortex?
six (however, layer four is split into 4a, 4b, and 4c)
where do inputs enter the visual cortex?
usually layer 4
where do layers 5 and 6 of the visual cortex project to?
other parts of the brain
where in the visual cortex are simple cells found?
layers 4 and 6
where in the visual cortex are complex and end-stopped cells found?
layers 2, 3, 5, and sometimes 6
where do cells of the konicellular pathway (LGN) project to?
layers 4a, 2, and 3 of the visual cortex
where do cells of the magnocellular pathway (LGN) project to?
layers 4b and 4c of the visual cortex
where do cells of the parvocellular pathway (LGN) project to?
layers 2, 3, 4a, and 4c
true or false: center-surround cells can be found in the visual cortex
true! (in layer 4)
layers 2, 3, and 4b of the visual cortex project to:
other areas of the cortex
layers 5 and 6 of the visual cortex project to:
deep brain structures as well as other cortical areas
