Primary visual pathway Flashcards
Where is V1
in the occipital lobe
Where does the visual information start
Retina
Name the three cells in the retina in order
photo-receptors, bipolar cells, retinal ganglion cells
which cells does the optic nerve receive signals from
retinal ganglion cells
What are the two types of photoreceptors
Rods and cones
Which type of photoreceptor are more abundant and CANNOT discriminate colours
Rods
Which photoreceptor is sensitive to low light and sees colour
Cones
what do retinal ganglion neurons receive signals from and via what
from photoreceptors, via bipolar cells
what does the ON-OFF centre-surround receptive field in retinal ganglion neurons mean
Light in the ON regions excites the cell
Light in OFF regions inhibits the cell
what is the response rate of a cell based on
the sum of stimulation in ON region - stimulation in OFF region
What is the receptive field
the proportion of the retina/visual field in which visual stimulation will evoke a change in the firing rate of a given neuron
why is the luminance of features represented relative to their surround
to help preserve appearance of object regardless of light levels in the environment eg newspaper looks the same in dark as in bright sunlight
what are the three information processing stages in the primary visual pathway
Retina- lateral geniculate nucleus (LGN) - visual cortex
what do cones send inputs to
retinol ganglion cells and LGN
What explains negative after images
colour-opponency and firing-rate adaption (rebound effects)
What are the two main types of orientation- sensitive V1 neurons
Simple cells, complex cellls
Which type of V1 neuron have fields with inhibitory and excitatory regions (combining ON-OFF inputs)
simple cells
Which type of V1 neuron have no discrete ON and OFF regions
complex cells
what is a retino-topic map
orderly mapping of retina/visual field onto visual cortex
What is V1 divided into
small columnar modules that combine neurons sensitive to different aspects of stimuli
Where does the next stage of visual processing occur
in the visual association cortices (V2-V5)
What is blindsight
appropriate responses to visual stimuli when unconscious with lesions to primary visual cortex
What does blindness indicate
there are additional visual pathways apart from the primary visual pathways (critical for conscious vision
subjects behaviour can be guided by brain without conscious awareness
