Aliya's Vision Deck

Question 1

Average Field of Human View

Answer 1

Question 2

Fovea, Parafovea, periphery

Answer 2

Question 3

results of dark adaptation

Answer 3

Question 4

Rods v Cones

Answer 4

1. rods pool outputs to common ganglion cell more than cones do
2. rods take longer to adapt and longer to die than cones do
3. rods are more through the periphery and somewhat through the parafovea where cones are primarily in the fovea
4. rods are sensitive but cones have acuity

Question 5

LGN

Answer 5

Question 6

Organization of V1

Answer 6

1. Topographic map: adjacent things are adjacent
2. Cortical magnification factor: foveal reps are ‘expanded’ relative to peripheral reps
3. Cortex is organized into ‘columns’ that rep values of a feature (location, orientation, which eye it came from)
4. Types of columns: location (Columns of neurons that all have their receptive field on roughly same location on retina), orientation (Columns of cells that all prefer same orientation), and ocular dominance

Question 7

Simple Cells

Answer 7

1. Orientation: respond to edges/bars of specific orientation
   
   • Different receptive field structure than center/surround structure of cells in LGN
     
     • Edge v stripe detectors
2. Spatial freq
3. Phase SENSITIVE
4. respond to flickering lights

Question 8

complex cells

Answer 8

1. Orientation specific
2. care about SF
3. Most active when stimuli is moving
4. Some cells respond to any motion but others to specific motion direction

Question 9

End-stop Cells

Answer 9

1. Like complex cells but only to lines of certain length
   
   • Orientation specific
   • care about SF
   • Motion specific
   • Length specific
   • phase insensitive!

Question 10

HyperColumns

Answer 10

Hypercolumns: complete set of orientation and ocular-dominance columns for a given retinal location

• the whole thing is coding one part of the world that we see
• orientation changes gradually as it goes
• ocular dominance: L&R alternate

Question 11

after the V1

Answer 11

1. ventral v dorsal pathway
   
   • Ventral (what)
     • Shape and form
   • Dorsal (where/how)
     • Location
     • How to interact with something and thus where it is
       
       • How path is used to plan action
2. Extrastriate Cortex (beyond V1)
   
   • V2: illusory contours
   • V3: possibly combining info to construct 3D percpets
   • V4: color
   • MT (medial temporal): motion
   • IT (Infero Temporal): shapes, form, faces
     
     • FFA

Question 12

Basic Color Concepts

Answer 12

1. Color is not stable- it depends on both the properties of the object and of the light projected/reflected on it
2. Dimensions of light: wavelengths, how pure it is in terms of wavelength are important
   
   • Usually described by hue, saturation and brightness (psych dimensions of color)
   • Mapping exists between these dimensions and physical properties of light
3. Hue: wavelength
4. Brightness: intensity of light
5. Saturation: how pure is distribution of light (one wavelength or lots of wavelengths?)
   
   • Lots= broadband
   • Saturated= primarily one wavelength

Question 13

Fruit theory of original color vision:

Answer 13

1. If you’re a person thousands of years ago and are really hungry and must tell where to walk for food, the berries’ color makes them pop out
2. So it’s important and provides info to help with survival
   
   • 1) Also allows you to ID objs
     
     • -in wrong colors, fruits take longer to name
   • 2) Fruits:
     
     • -are they ripe/not ripe?

Question 14

Color mixing experiments:

Answer 14

1. mixing oils or water colors
   
   • you get a diff color when they mix
2. Mixing lights
   
   • It matters whether you’re combining colors or pigments
     
     • Combining lights: additive
     • Combining colors: subtractive

Question 15

Color Contrast

Answer 15

1. Happens when eyes are open so at all times
2. Simultaneous and successive
   
   • Simultaneous: we perceive them as different based on their backgrounds
     
     • Known as such because they’re seen at the same time
3. Successive: aftereffects/ after image
   
   • Your cones are tired and fall below baseline which is why we can see the other color

Question 16

Problem of Univarience

Answer 16

1. “Hypothetical prob that explains why we have 3 cones”
2. We have blue and orange light
3. For these receptors they don’t tell your brain a color they tell it a number-> the number is how many times the neuron fires
4. Problem: blue and orange are same number of button presses
   
   • To exacerbate problem: depending on quality of light (e.g. brightness) it’ll change the number of fires that occur
     
     • Additional Problems: color ambiguity and ambiguity within color itself
5. We were talking about the M cone where the blue and orange fire the same amount
   
   • But for blue we have a high S, med M, low L
   • But for orange we have a high L, med M, low S
   • So it takes three signals for brain to know which color it actually is

Question 17

Trichromacy

Answer 17

1. Trichromacy gets us around the problem of univariance
2. Questions
   
   • 1:1 mapping from wavelength to cone responses?
     
     • Yes it’s 1:1 because pattern of cone type is fixed
   • is mapping from cone response to wavelength 1:1?
     
     • Most of the time it’s 1:1 except metameres
     • Metameres: general term in color which is different color stimuli (diff types of light) that give same experience of color
       
       • Because brain can’t see outside world, it just reads electric signals from eyes
   • do patterns always respond to a single wavelength?
     
     • No there are patterns that only come for combination of lights
   • Non spectral hues

• Every wavelength is matched with a color but not every color you see is matched with a wavelength
• Magenta is a variant of purple; this is S & L cone (blue and red) combined
• So every color you see is 3 numbers for your brain