seminar 6 - claudia racca Flashcards
the striate cortex is organised in ocular dominance columns alternating between…
left and right eye
which layer in V1 is split into column
layer 4C
the cells in layer 4C are monocular meaning..
they see information from only one eye (because of the column)
cells in V1 are each wired up to a..
photoreceptor in a particular region of the retina
nearby photoreceptors are connected to nearby…
neurons
primary visual cortex maintains the topographic mapping of the visual world.
more cortical area is devoted to which part of vision
the fovea (center)
neurons in the visual cortex have more selective responses than ganglion cells and lateral geniculate neurons. for example…
- can detect bars and edges, not spots
- the specific position of stimulus in receptive field
- the specific orientation
- the specific direction
receptive fields of layer 4C neurons are similar to LGN neurons but layers outside 4C have receptive fields with…
new characteristics
what does binocularity mean
in V1 inputs from left and eyes are combined
in layer 4, inputs come predominantly from one or the other eye. this is called
monocular
outside layer 4 neurons have two receptive fields, one in ipsilateral eye and one in the
contralateral eye.
there is input from the left and right eye into layer 4C. layer 4C will project to other layers (e.g layer 3) where the cells receive _________ input
binocular
which layer in 4c is insensitive to the wavelength
4calpha
which layer in 4c has center surround colour opponency
4cbeta
outside layer 4c in v1 we find oriented receptive fields for the first time. what does this mean
cells no longer respond best to circular spots of light but to elongated bars of light moving across the receptive field. these neurons exhibit orientation selectivity (responds to specific angle of the bar)
cells with similar orientation preferences lie in the same…
column
some of the neurons that are orientation selective are also….
direction selective
receptive fields in V1 cells can be simple or complex.
simple responds to…
bars of light with a specific orientation
complex responds to….
a moving light stimulus of a particular orientation and direction of travel
simple cells
sum of inputs from LGN neurons with neighbouring/aligned receptive fields build an elongated receptive field that is most responsive to elongated bars or edges
and simple cells are most responsive to a specific orientation of the bar
complex cells
- receive input from simple cells
- orientation selective
- no ON/OFF subregions
- nearly all binocular
- perform length summation
hypercomplex cells
like complex cells with inhibitory flanks on the end of the receptive field
response increase with increasing bar length up to a limit and the response is inhibited
simple, complex and hypercomplex cells can work together to decompose the outlines of a visual image into short segments. this is the basis on simple and complex object recognition
what is a hypercolumn
a set of columns responsive to lines of all orientations from a particular region in the visual fields and viewed by both eyes
