seminar 5 - claudia racca Flashcards
what is vision
the transduction of visible light into neural signals, creating the perception of ‘what’ is ‘where’
the visual pathway:
the signal is sent from the retina down the optic nerves. the point where the two optic nerves meet is called the
optic chiasm
in the optic chiasm there is a…
crossing of some of the axons into the other side
what field of vision crosses over
the nasal field.
therefore everything from the right visual field goes to the left and everything from the left visual field goes to the right
therefore the right visual hemi field is view by which visual cortex
the left visual cortex (and vice versa)
the optic tract the goes through what part of the thalamus?
the lateral geniculate body
the lateral geniculate nucleus (LGN)
- there are two of them (one for each side)
- projections are kept separate in contralateral layers and ipsilateral layers
- contains three different types of cells, corresponding to three different types of layers
- maintains topographic mapping of the visual world
how many layers is the LGN divided in to
6 layers
there are projections to each layer from different parts of the retina
information from the contralateral eye foes to layers…
1, 4 and 6
information from the ipsilateral eye goes to layers..
2, 3 and 5
segregation of input by retinal ganglion cell type:
M type retinal ganglion cells project to layers…
1 and 2 (magnocellular layers)
P type retinal ganglion cells project to layers…
3-6 (parvocellular layers)
6 koniocellular layers which are…
in between the other layers
all LGN layers project to the…
visual cortex
what does the LGN do
brings retinotopic maps from both eyes into register to make it easy for the cortex to combine inputs from the two eyes
the visual cortex has five areas
V1 (primary visual cortex) to V5
different names for the primary visual cortex
V1
striate cortex
broadmann area 17
the primary visual cortex is at the back of the brain and runs along the…
calcarine fissure
retinotopy:
neighbouring cells in the retina relay information to neighbouring places in different brain structures (LGN, V1)
the retinal foveal area is ________ in central targets
magnified
how many layers of V1 are there
6
layer 4 is subdivided into a, b and c
and the c part is further divided into…
alpha and beta
why is layer 4 important
it is where the input from the LGN comes into the visual cortex
what is the stria of gennari
band of myelinated axons from LGN cells running parallel to the surface of the cortex along calcarine fissure of the occipital lobe
there are three basic types of neurons in V1
spiny pyramidal cells
spiny stellate cells
smooth or sparsely spinous interneurons
spiny pyramidal cells are…
excitatory and mainly outside layer 4C
spiny stellate cells are…
excitatory and mainly in layer 4C
smooth or sparsely spinout interneurons are…
almost all GABAergic and in all layers
the magnocellular layers in the LGN (layers 1 and 2) project to which layer in V1
4Calpha
the parvocellular layers in the LGN (3-6) project to…
4Cbeta
koniocellular layers project to…
layer 2 and 3 in V1
layer 4Calpha then projects mainly to…
layer 4B
layer 4Cbeta then projects mainly to…
layer 3
outputs of V1
layers 2-3 and 4B pyramidal cells output to other cortical areas
layer 5 pyramidal cells output to the superior colliculus and pons
layer 6 pyramidal cells out put to the lateral genicular nucleus
in layer 2 and 3 of V1 there are cytochrome oxidase (CO) blobs.
what are they
a mitochondrial enzyme used for cell metabolism
CO blobs correspond to neurons with a high concentration
CO
between blobs there are
interblob regions
blobs receive direct input from…
LGN koniocellular layers and parvocellular and magnocellular input from layer 4C of V1
