Perception in cortex Flashcards
How many cells in retina?
126 mil
How many cells in Cortex?
250 mil
How many layers in V1?
6
How many layers in Cortex?
6
How many cells in V1?
150 mil
Tell me about stellate cells
Intracortical
Connect LGN and pyramidal
Tell me about pyramidal cells
Very long
Apex Out
Connect extrastriate to LGN
Tell me about layer 1 of V1
1,2,3 go to extra striate
4,5,6 go back to LGN
Strongly influences deeper pyramidal cells
Role in visual attention and neglect
Thick and thin stripes
What is the V1 layer 1 made up of?
Synapses of Extra striate and pyramidal and
LGN and pulvinar
What’s up with V1 layers 1 and 2?
Where projections start (Full neurons here, only synpases in V1)
Also role in binocularity and figure-ground
Magno to V5
Parvo to V4
Purpose of Layer 4 and what’s it broken into?
Input layer - info to extrastriate or retinal tectal
Broken up into
4a
4b: Goes to V5/MT and superior colliculus
4c(a)
4c(b)
V1 layers 5 and 6 do what again?
Loop back to retinotectal/retino geniculate (LGN+Pulvinar)
Layer 6 is the neural loop and takes info from LGN back.
Deeper layers will send info from cortex to LGN
Obvi helps with saccades
What the eff are Meynert cells?
Cells of V1 layers 5 and 6 that go from V5/MT to superior colliculus
Where’s the Line of Gennari
Demarcation in V4 where input from the LGN to the cortex goes 4a: From Parvo 4b: From V5/MT 4c(a): From Magno 4c(b): From Parvo
Which layers of V1 go to extrastriate? Where do they go?
1,2,3
V2, V3, V4, V5
Which layers of V1 go back to LGN?
4: input
5 & 6 go back to LGN
How much of the cortex is central vision?
2/3
What’s cortical magnification
Cortex cares more about foveal vision. Magnified in importance while periphery fades
How is the visual cortex arranged?
Layers 1-6
Then columnar packs of gum alternating between eyes
Where are the cortical blobs?
Going down columns of V1. See color so only seen by Parvo stream.
What dye is used to visualize cortical blobs and how does it work?
Cytochrome oxidase stain
Dies areas that use lots of ATP
What types of fields to cortical blobs have?
Same as photoreceptor fields upstream. Red/green fields
What are the 3 cortical cells Hubel and Wiesel found and which one doesn’t exist
Simple
Complex
Hypercomplex doesn’t exist
What do simple cells do
Fire APs when visual stimulus in certain orientation
Where do signals to simple cells come from?
Summate signals from LGN to a simple cell
What types are there?
On and off as well as simple edge detectors
What do complex cells do?
Only fire APs when orientation and movement of stimulus is correct
If goes opposite direction, will flatline
Whatre endstops?
Limits to how long a stimulus can be before signals start to weaken. Found in simple and complex cells
Previously mistaken for hypercomplex cells
How much space does binocularity take up in the visual cortex?
2/3
Where does binocularity first occur?
Visual cortex
What’re the types of stereo cortical cells?
Course stereo and fine stereo cells
What’re the course cells?
Car driving cells
Also lets you do magic eye
2 types of course cells
Far course: beyond line of site. Inhibited if within line of fixation
Near course cells: Excitation and inhibition reverse far
What’s responsible for the magic eye effect?
Course cells
What percentage of stereo cells does course cells make up?
30%
What do fine stereo cells do?
Needle threading stereopsis
What’s the difference between fine tuned excitatory and fine tuned inhibitory stereopsis cells?
Excitatory: Excited with specific disparities up to 1 degree
Inhibitory: inhibited with stereo disparity
What percentage of stereo cells is tuned excitatory?
50%
What percentage of stereo cells is tuned inhibitory
20%
What happens with short term abuse of visual system?
Complex cells tire out and get motion receptors to habituate. Get water fall illusion (V5/MT)
What happens with long term abuse of the visual system?
Amblyopia! Can be meridional
If certain oriented edge detectors aren’t stimulated, will also switch directions
