L3 Flashcards
how does the visual world map onto the retina
it is inversely projected onto the retina
where do 90% of the fibers in the optic nerve terminate
the lateral geniculate nucleus of the thalamus
what allows for mapping of the visual field
the response of cells in the LGN (on and off centre surround)
what is on centre
when light of the correct orientation falls onto the centra it will increase the cells firing rate and when it falls on the surround it will decrease the firing rate
this is the opposite for off centre
what is retinotopic organisation
the visual world is mapped onto the retina > LGN relationships are maintained in the nervous system
what is the patteren for LGN retinotopic mapping
how will the cells be active hen something moves across the visual field
when an object moves across the visual field the cells that respond are usually in a linear pattern
where do fibers from the LGN project to
V1 / striated cortex / brodmann’s area 17 / primary visual cortex
where is V1 located
at the very back of the occipital lobe. you cant see most of it as it is on the inside of the brain
what cells are found in V1
simple and complex cells
what is a simple cell
these respond to elongated bars or edges of light
these are orientation selective and have separate on and off subregions
these cells can be binocular or monocular
what are complex cells
these are orientation selective
have spatially homogenous receptive feild therefore they have no sporate on/off sub regions
nearly all of these cells are binocular
list the order of cells information passes through in the brain
retinal ganglion cell –> LGN –> simple cell –> complex cell
what is meant by the columnar architecture of V1
the cortex has many layers. if you look at cells at right angles to the surface to see what they respond to, they all have a receptive field which overlaps and they all have the same orintation selectivity (they all involved in processing the same part of the visual field)
when you look at cells in the horizontal plane they shift systematically and as the position of the receptors fields and preferred orintation slowly change. this shows that the cells respond to slightly different things indicating that they are responsible for a different parts of the visual world
what does retinotopy mean
remapping of the retinal image onto the cortical surface
which region of the retina has a greater magnification factor (used more of V1)
the foveal region
a local group of neurons in V1 represents what
a point in the visual field
what is an example of topographic organisation
retinotopic mapping