Central Visual Processing I Lec12 Flashcards
The retina ganglion cells have 3 pathways:
magno, parvo, k pathway
Visual fields are ___ and ___ in the retina.
flipped and inverted
in the optic chiasm, ___ axons cross
nasal axons (temporal visual field)
nasal axons carry information from the
temporal visual field
in the optic chiasm ___ axons stay ipsilateral
temporal
LGN has 6 layers
the 2 magnolayers are ___
ventral
LGN has 6 layers
the 4 parvo layers are ___
dorsal
in the lgn, the inputs are segregated by
eye
lgn gets feedback input from
V1’s layer 6
V1 is ordered ____
retinotopically
in v1, more cortical area is given to
central vision/fovea
order of M,P,K in V1
M, P, and K pathways mix substantially here
M pathway is still partially seperated to provide a fast motion processing
All V1 neurons have retinotopy which is a ___ field position
receptive
V1 neurons are that orientation tuned
interblobs
look at angle of a light bar –> edges
V1 neurons that are center/surround
blobs
The V1 functional unit is a ____
hypercolumn
Ocular dominance hypercolumn =___ and ___ columns
right eye column + left
eye column
A complete hypercolumn =
ocular dominance hypercolumn
+ orientation hypercolumn + color blobs
One hypercolumn contains all the cortical machinery to fully analyze one point in visual space for all ___ and ___
orientations and both eyes
Input from optic radiations goes to___ in V1
layer 4
Output of V1 going to V2 leaves from ___
layers 2&3
Output from V1 to superior colliculus leaves from
layer 5
Feedback from V1 back to LGN leaves from
layer 6
___ has large (1.5mm) stripes that stain with cytochrome oxidase
V2
Dorsal pathway to ____ visual cortex
parietal
Ventral pathway to ___ visual cortex
temporal
the where pathway is the
dorsal pathway
the what pathway is the
ventral pathway
the where pathway is involved with
motion and
object localization
the what/ventral pathway si involved with
pattern and object recognition.
As you go to higher cortical areas… ___ integrate, summate, and enlarge
Receptive fields
lesions in higher cortical areas (above v1) usually manifest as specific visual deficits like
loss of color vision or form vision
lesions in V1 manifest as__ or ___
blindness or scotomas
ganglion cells in the retinal detect what (4)
spatial representation (receptive fields & retinotopy)
• retinotopy - the mapping from the retina to initial neurons
- luminence / intensity (esp. rods)
- spectral absorption (cones, color)
- spatial contrast (center/surround, ON/OFF,
edges)
spatial contrast is related to
center surround receptive fields
output from the retinal ganglion
- lgn
- superior colliculus
- hypothalamus
- pretectum
what is another name for the retinogenciulate pathway
the visual processing pathway
the superior part of the viosual field lands on the ___ part of the retina
inferior
right superior field projects on to the ___ of the retina
bottom left of the retina
first neurons that get binocular input are in the ___
striate cortex, not the lgn
the left visual field gets represented in the ___ hemisphere
right
X optic nerve —>
complete scotoma
X optic chiasm:
bitemporal hemiopia.
X optic tract on the right
lose left visual field
lesion of optic radiations
Quadrantanopia
leison of occipital cortex typically causes ___ hemianopias
macular sparing
If Meyer’s loop (temporal pathway) is lesioned, the Quadrantanopia is ____ superior
if Baum’s loop (parietal pathway) is lesioned in the optic radiations, the Quadrantanopia is ___
inferior
lgn cells are binocular or monocular?
monocular.. they have functional segregation
the __ pathway is very important for motion
M
the __ pathway is involved with visual acuity & color
P
the ___ pathway is involved with temporal resolution and luminance contrast
m
Common properties of receptive fields in the retina and LGN (3)
center surround organization
mix of cells with on/off center
retinotopically ordered
what may be color opponent (red/green or blue/yellow)
retinal ganglion or LGN
within the ocular dominance columns are the ___ columns
orientation
an on cell you get AP when light is shown in the
center
each visual ___ neuron has a receptive field which is part of a retinotopic representation
and has receptive field proepries such as ocular dominance, orientation, and perhaps
other properties
cortical
with ___ you dont see red without analyzing green as well
color opponency
type II color opponentn cell is depolarized with __ and hyperpolarized with ___.
red and green
doube opponent receptive fields encode both __ and ___ contrast
spatial and chromatic
e.g. in center red is on, green off
in surround red is off and green is on
type ___ cells have spatial opponency and a weak color bias
type 1
___ can be type 1, type 2, or double opponent
blobs
are blobs monocular or binocular?
monocular
what is “oriented in V2?”
thick disaprity and pale
bilateral X of the ___ leads to a behavioral deficit ina task that requires the discirimination of objects
temporal lobe
bilateral X of the ___ leads to a behavioral deficit ina task that requires the discrimination of locations
parietal
The Magno system is specialized for high ___ and ___
temporal resolution (speed) and higher contrast gain,
The K pathway is probably also specialized for ___ perception.
color
what has center surround reeptor fields?
LGN and the retina
Within __, the M, P and K pathways intermix substantially
V1
V1 is highly __, with more cortex devoted to central vision.
retinotopic
The anatomical structure of V1 is a 2mm thick sheet of cells, with__ layers
6
If you record from a V1 neuron, if may have ___ domiannce or be ___
ocular domiannce or be binocular
instad of center surround receptive fields, cells of v1 have ___ receptive fields
oriented
Orientation tuning refers to the preference of a cell to be stimulated by an ___ of light presented at a particular angle
edge
There are some V1 neurons that are not orientation tuned, but have center- surround receptive fields and are___
color-opponent
The ocular dominance (OD) columns alternate between
left and right eye
Neighboring columns of oriented cells in v1 usually have similar but slightly different ___ tuning
orientation
So in general V1 neurons have, simultaneously,
- a receptive field position (reitnopathy)
- an ocular domiannce
- preferred orientation
The segregation between the color blob
cells and the regular, oriented V1 cells found in the “interblobs” is the beginnings of the segregation between the “___ and ___
form” vision and color vision pathways,
collection of orientation columns that would cover all the possible orientations, from horizontal through vertical and back, for a
given point in visual space.
The orientation column map and the ocular dominance column bands are interwoven in V1 and run
at right angles to eachother
There are two major visual processing streams after V2: the___ and ___ pathway
dorsal pathway and the ventral pathway.
V1: blobs -> ____ stripes in V2
thin
V1 interblobs -> ___ (inter) stripes in v2
pale
layer 4B in V1 -> ___ stripes in V2
thick
what is retinotopically organized?
v2 and v1
The V2 pale stripes contain oriented cells, often end-stopped and probably involved in the detection of
curvature.
The V2 thick stripes contain oriented, disparity cells and are probably involved in
stereo depth vision.
