Central Visual Processing I Flashcards
How many layers are in the LGN? How are these layers divided?
6 layers
2 are magno (ventrally) and 4 are parvo (dorsally) with konio layers interspersed between
From ventral to dorsal: Contra-Ips-Ips-Contra-Ips-Contra
How many layers are there in VI?
6
What layer of V1 does the LGN enter into?
Layer 4
The part of the visual field that a given neuron responds to within the visual cortex is defined as:
Receptive field
The mapping of a visual input from the retina to V1 is defined as:
Retinotopy
The amount of cortex that is designated to a given part of the visual field depends directly on what?
The density of photoreceptors in the retina
The majority of the visual cortex is devoted to what part of the retina?
The fovea which has the greatest density of photoreceptors (especially cones)
What are the different names for the visual cortex?
Striate or Brodmann area 17 or V1
From the optic tract, axons project into a number of targets. What are some of these targets?
Superior colliculi (important in orienting motion of the head with eye movements) Pretectum (important for pupillary and lens reflexes) Hypothalamus (regulation of Circadian rhythms) Thalmogeniculate nucles (LGN) image processing
What is the primary visual processing pathway?
Corticogeniculocortical pathway (LGN)
What is the first area that joins the information from both the right and left eye to get binocular vision?
V1
There are three different types of cone classes. What are they?
R (long), G (medium), and B (short)
Where do the M, P, and K pathways originate? Where do they terminate?
Originate in the retina and terminate in the visual cortex
What type of visual information does the M (magna) pathway predominately perceive?
High temporal resolution (speed) and motion
What type of visual information does the P (parvo) pathway predominately perceive?
High visual acuity and color
What type of visual information does the K (konia) pathway predominately perceive?
Color
The LGN received feedback from which layer of V1?
Layer 6
True or False: The LGN has center-surround receptor fields
True- just like the retinal ganglia
Which layers of V1 go onto the extrastriate (V2)?
Layer 2 and layer 3
What is ocular dominance?
The predominant eye that is used to see something a certain receptive field
What is orientation tuning? How does this relate to action potentials?
Neuron is stimulated by the edge of light when the light is presented at an optimum angle, which produces more action potentials
Some V1 neurons aren’t orientation tuned but rather have receptive fields that allow them to be color selective. What are the two different color signals?
- Red- Green
2. Blue-Yellow
True or False: V1 neurons have center-surround receptive fields?
False: with the exception of the neurons responding only to color
Every V1 neuron has three different components that make it unique: what are these components?
A specific receptive field position (retinopy), an ocular dominance, and a orientation position
What do CO blobs that are interspersed between the orthogonal columns of ocular dominance and orientation position represent? What types of vision do these CO blobs perceive?
Long term metabolic activty
CO blobs perceive monocular, color vision
A collection of functional cortical columns that covers the entire range of possible values of a given stimulus parameter is the definition for what term?
Hypercolumn
All of the orientation positions for a given point in visual space is the definition for what term?
Orientation hypercolumn
A complete orientation cycle- or one orientation hypercolumn, takes up how much distance within V1?
1mm
A complete set of cortical columns handling both the right and left eye for a given point in visual space is the definition for what term?
Ocular dominance hypercolumn
A complete ocular dominance hypercolumn requires how much distance within the VI?
1mm
If you were to cut out a 1mm x 1mm chunk of VI, what would this give you?
All of the possible orientations that can be seen through both eyes for a given point in the visual field
What are the two major processing pathways from V2?
- Dorsal pathway
2. Ventral pathway
What is the dorsal pathway responsible for? What does it connect?
Motion and location (the where)
Connects V2 to the parietal visual cortex
What is the ventral pathway responsible for? What does it connect?
Pattern recognition (the what) Connects V2 to the temporal visual cortex
How are CO different in V2 than in VI?
In V2 CO are stripes, in VI CO are blobs
The thin stripes due to the CO blobs in VI, contain cells for what kind of vision in V2?
color
The pale stripes due to interblobs in VI, contain cells for what kind of vision in V2?
Detection of curvature
The thick stripes of V2 contain cells for what kind of vision?
Depth perception
What is more retinotopically oriented: VI or V2?
VI
As you move up the higher extrastriate layers, what happens to the retinotopy and the receptive field?
Retinotopy decreases while the receptive field increases
What are the four layers of ordering in V1?
Retinotopy, ocular dominance, orientation, and CO blobs
A bilateral lesion of the temporal lobe will result in what with regard to higher vision?
Inability to discriminate between objects
A bilateral lesion of the parietal lobe will result in what with regard to higher vision?
Inability to discriminate locations
