Chapter 6 visual system Flashcards
___ is also known as the blind spot
Retina - everyone has a spot in their retina where the optic nerve connects. In this area there are no light-sensitive cells so this part of your retina can’t see. We call this the blind spot.
where does axons of the receptors leave the eye and form the optic nerve,?
Optic disk:
We are blind to any objects
whose image falls on which part of the retina?
Optic disk? why - no photoreceptors - The CNS fills it in.
What is a fovea specialized for ?
- The fovea is specialized for high acuity, color vision in bright light -
where is fovea located?
A yellowish circular area near optic disk is macula and the center is
fovea
True or false - The center of the fovea contains only rods.
False - cones
Which area is good for vision in lower light?
coutside the macula. - coz the * The rod density reaches maximum
there are ___ type of neuronal cell
5
The axons of ganglion cells leave the eye as?
Optic nerve
What is the direction of Neruonal communication and direction of light ?
neuronal - photo - bipolar - ganglion , opposide for dol
Rods only respond to up to?
moonlight level of light intensity
True or false Spatial resolution in dim light is poor.
True
Rods respond faster than cones. True or false
False
cones are more sensitive than rods true or false?
false - Cones are less sensitive. They require moonlight or greater levels of
illumination to function
mix & match cones for color vision Long-wavelength cones, , Middle-wavelength cones, . Short-wavelength cones,
red,green, blue
What causes receptor potentials in rods and cons
- Photons are absorbe
What causes receptor potentials in rods and cons
- Photons are absorbed
why is there constant appearance of objects despite varying illumination?
This is because the visual system is attuned to the detection of borders, between light and dark areas, or areas b/w diff colours.
true or false * Neurons at each level of the visual system has a RF.
True
What is the primary visual cortex,
around the calcarine sulcus also called?
striate cortex
__ contributes to guided eye movements
superior colliculus
what is LGN and where is it located WHat happpends to optic fibres/ nerves her
lateral geniculate neucleus, thalamus located. they stop
- LGN neurons do not reach adult size until ___ years.
2
Only ___ 10 % of inputs to LGN come from the
, ___ from cortex of the brain
retina, 90%
how many layers does LGN have ?
6
Retinotopic mapping at V1
What are layers 1-2 , 3-6 called?
parvocellular and magnocellular
what is functions of parvocellular?
Orientation discrimination in very young infants
* Color discrimination in 4 week olds
Magnocellular functions develop later, which are?
Direction selective responding to motion in 6 to 8 week olds
* Depth processing in 3 to 4-month-old
True or false - Orientation columns: Neurons
located above and below one
another in the same column
have different properties.
False - Orientation columns: Neurons
located above and below one
another in the same column
have similar properties.
What are color blobs?
They are dark regions in
the left image - * Color sensitive * In layer II and III in V1
where- superior longitudinal fascilusMix and match 1. * Orientation columns,
2. * Color blobs
3. * Ocular dominance columns
1. * receive input from one eye- Depth perception
2. * Sensitive to color
3.discriminatory on spatial
orientation
1-3, 2-2 3,1
Which brain structures are associated with where and what pathways?
superior longitudinal fasciculus and posterior parietal cortex. What - inferior longitudinal fasciculus , inferior temporal cortex
what pathway fucntion?
– Tracking moving objects, relative motion information
What pathways?
– Hierarchical representation as proceed more anterior: feature to object
What is the route of the where pathway?
dorsal pathway to V5/MT then to posterior parietal cortex
what is the route of what pathway?
ventral pathway , through v4 to inferior temporal cortex
- fMRI reveals double dissociation between the two pathways true or fale?
true
