Lecture Flashcards
1
Q
Insulin Resistant Diabetes
A
- with age, body stop producing insulin so there are circulation problems in the eyes
- capillaries beging to leak and bleed so it causes floaters in the vitreous humor
AGE RELATED
2
Q
Neo-vasularization
A
- new blood vessels being to grow bc the eye uses alot of blood but these are abnormal and leak too so it accelerates the problem
- can scar retina and lead to blindness
- LIFESTYLE PROBLEM
3
Q
Treatment for neo-vascularization (2)
A
1) retinal photocoagulation: use laser to kill off abnormal cells - SHORT TERM
2) ran-retinal phtocogaulation: use laser to burn off the retina so it uses less blood
4
Q
Macular Denegeration
A
- cell sin fovea die and destroys cones - less detailed vision
- OCCURS WITH DIET AND AGE
5
Q
Drusen
A
- white yellow bumps in between retina and pigment epitliu are afected - cones in fovea die off first
6
Q
What test is used for macular degeneration?
A
- Amsler Grid Test: black dot in middle with lines - if you have macular degeneration then the lines look wiggly because cones are dying
7
Q
2 types of macular degeneration:
A
1) Dry: progress slow and person may not notice - get eyes checked
2) Wet: loose your vision and neo-vasularization speed up loss of sight (leaks and cause floaters)
- will lead to blindness
8
Q
What is the treatment for wet macular dengeration?
A
- Destroy the choloroid because it is responsible for nourishing blood
9
Q
Describe hereditary retinal disorder
A
- affects the rods
- begins in teen - start noticing problems with night vision
- don’t see color in the far peripheral (no color in rods)
10
Q
What is glucoma?
A
- When the acqueous humor lique gets trapped
- in between cornea and lens there is liqued but it gets blocked on the way out
11
Q
2 types of glucoma:
Who is at risk for close gulacoma?
A
1) open angle: slow, on the way out it gets blocked and presure builds up and pushes against the vitreous humor and retinal ganglion cells
- can cause BLINDNESS
- can help control you BP
- most common type
2) close angle: the iris flops over and blocks the fluid so it developes really fast; can feel it = PUPILLARY BLOCK
- need to put a hole in iris so the fluid can esacpe = IRIDECTOMY
- asians and people with axial ayopia (short eyeballs) at risk
12
Q
Afterimage
A
- image you see floating in front of eyes from an after-effect
13
Q
After-effect
A
seeing one things influences what you see later
14
Q
Using B&W; how does an after-effect occur?
A
- when your eye sees white it receives alot of AP so the white neurons get tired out and then you see black
- the dark neurons are not as tired so they can active AP where there is white space
15
Q
What are 2 ways collector cells work?
A
1) conveergence: adding up actvity of many cells (more sensitive in dim light)
2) Spatial lateral summation
16
Q
What is lateral inhibition?
A
- when cells are side by side they send inhibitory NT to eahother so that you can see edges
17
Q
Describe the visual system of the Limulu scrab
A
- have lens retina pairs (similar to neurons) called ommaditium that are connecte to eachother with a laterla plexus
18
Q
What are 3 illustions that demonstrate lateral inhibition
A
1) Mach bands - exaaggeration of edge in our perceptio
2) Herman Grid - the center of the interesection has inhibitory NT from all sides = small gray circle
3) Simultaneous contrast: the small sqaure in the white surronding looks darker because of laterla inhibition
19
Q
Receptive field
A
- part of retinal image that cell response to
20
Q
On/off response
A
On response: when there is light the cell produces more AP than baseline
- nothing happens in darkness
Off response: when the light is on it produces less AP than baseline
- nothing happens in the dark
21
Q
2 types of retinal ganglion cells:
A
1) Parvo cell: small axon; color senstivity; high acuity; sustained response to stimuli (continuous responding)
2) Magno cell: faster bc axon is wide; motion; fewere m cells but many in periphery (fast response to a baseball coming towards the side of your head)
22
Q
Retinotopic map
A
- sptial realtion in retina are presevered in brain (things closer toether in image = close together in brain )
23
Q
Feedforward
A
- bottom up pocessing
- going from the eye to the brain and bi-directional
24
Q
2 ways that coding can work:
A
1) specficity coding: firing of 1 neuron in response to specific stimuli (key to sensory coding)
2) distributed coding: cell respond to different degres to same stimli (can look at pattern of responding)
25
Tilt after effect
- when you stare at lines to the right for a long time these receptors get tired out so when you look at line that are vertal the right orientation is too tired to balance out the left orientation so the left is responding more strongly and makes the lines tilt to the left
26
Optic chiasm
- firs stop from the visual field that connects both visual fields
27
Suprachaismitc nucleaas
- first visual strcuture of the visual pathway hat controls circaidum rhythm to send signals to pineal gland and produce melatonin
28
Melanopsin
- special retinal gaanglion cell in the suprachaiastmic nucleas that tells us if we are sleeping or not (photopigment)
29
Center surrond antagonism
- if + in center and light hits center = more activity; light in exterior when exterior is - slows down actiity; light everyone = cancels out activity
30
What structure comes after optic chiams? Descirbe it and the system it belongs to
- superior colliculus: specailized for eye movements
| - is part of the tecto-pulvinar system: has 10% of fibers and contains all m-cells
31
Extracular muscles:
- outside the eye and move eyes left and right
32
Fixation cells (superior colliculus)
- have Ap at stimulus when eye is fized at point
33
Build up cell (speruior colliculs)
- just before en eye movment = AP
34
burst cell (superior colliluc)
- when you are making eye movments = AP
35
Corrs-odel sensory
- integrates haring and visiion
36
Visual orientating reflex
- mediated by superior collculus; cross model because it itegrates hearing and vision to respon at once = communication between the 2
37
Geniculostatie system (2 components)
1) lateral geniculate nucleas
| 2) stratie cortex
38
LGN
- 90% of fibers that don't go to tectno pulvinar system (superior colliculs) go here
- 1 on each side of braint hat controls what information gets in
- LGN reduces activity when you are tired
- senstive to state of arousal bc recieves information from reticular formation and reticular activing system
39
Layers of the LGN
- 6 layers
- 1 and 2 = m cells (input of motion)
- 3,4,5,6 = p cells (form and color)
- 1,4,6 = contalateral eye information (opposite eye)
2,3,5 = ispilateral eye information
40
Straite cortex
- AKA primary visual cortex, V1, Area 17
- main part of visual analysis (conscious perception)
- take information apart and does a feature analysis
41
Feature analysis
- looks at entie image and looks at aspects e.g. feature orientation and particular types of movemenet
42
Cortical magnification
- fovea cones ahve their direct line to ganglgion cells so the brain has a disporoption amount of area dedication to the foevea even thought fovea = 1/100% the brain area = 8% so you can see finer details
43
Scetoma (dmanage to V1)
- small spot of dmaage = gap in visiual field
44
Hemianopia (damange to V1)
- half of visual field is damange
45
Quadromanopia (dmaange to V1)
- quater of visual field is lost
46
What happens when the entir visiual field is dmanage?
- leads to cortical blindness
- they have blindsight that suggest that they can still see something (perhaps because 10% is going to the tecto-pulvinar system)
47
Hubel and Wiesal
- did alot of work on feature analysis in the straite and found that single cells repond to different things
48
Simple cells
-respond to line orientation
49
Complex cells
- respond to combintation or line and movement
50
Hypercomplex cell/end stop cell
- look for length or angel
51
Hypercollum
- organization of slab of cell that respond to one location in visiual field (have specifici location and specific oriention loated inside the location (10 degree)
- ocular dominance inside the colum
52
What 3 sources of information are in the hypercolumn?
1) location
2) orientation
3) ocular dominance
53
Zeki Addition to the Hypercolumn
- tht blobs show up as you stain them = blobs are color sentiive cells
- area inbetwene is not color senstivie
54
Sptial frequency
- high contrast and low contrast lines
- related to the # of countours per unit in area (cycle/2 degree)
- low SF = bars farther apart
- high SF = bars closer together
- the more pieces you divide into lines = the higher the resolution
55
How to meausre contrast
= difference in birthness/sum of brightness
| - the recirporcal = senstivity
56
Grating (2 types)
- simplied stimulus
1) square wave: sudden changes in birthness
2) sine wave: gradual changes in brightness
57
Cycles
- dark and light bar together to measure the SF
58
Degres o visual aangel
- how many degres out of 360 does the stimuli cover (how many lines wtin this area is measured in degree)
- thumb wqill cover 2
- use cycles/2 degree to get degress ot visual agnel
59
Fourier
- any complicated prolem can be considered a sum of bunch of simple problems
- Fourier analysis = breaking down infmaorion into diff. level sof SF and SIN waves
- idea that visual cortex is also taking apaer a) line orienations b) SF c) contrast (cell looking at these)
60
How do you measure sensitivity to SF?
- using a contrast senstivity function (CSF)
- start with particular SF tat is really soft than you slowely increase it and measure when the person sees it for their contrast threshold = smallest difference you can see
- the senstivity is the recipricol
61
Metamers
- images that are different but they look the same
62
Species difernces in SF
- in cats you can measure SF by having them put their paw where the stripes are (reinforced with food)
- the can't see high SF so the confuse 2 images but they can see really good low SF
63
Age differences in SF
- metamers in babies are intense
- measured with preferential looking study that they will naturally look at most complex thing
- slowley reduce stripes until it is similar to gray and the baby looks at 2 thing equally
- babies need high contrast which is why they look at the side of your face (hair and forehaead)
- babies fovea are big and bulky so they don't have many = low SF
- younger person = high SF and loose high SF as you age
64
Lighting condition differneces in SF
- can see high SF in bright day light
- in mesopic conditions = middle SF (fake lighting)
- in night vision; seotpic condition (low SF)
65
Mesopic conditions
- fake lighting
66
Seotopic conditions
- dark lighting
67
What are hybrid images?
- When ther are 2 different SF in one image e.g. high SF = smiling; low SF = frowning
- we use low SF to see what people are feeling
68
What is a channel? How many do we ahve?
- group of neurons that respond best to sepcfic SF; we have 4-5
69
2 evidecen tat we have separate SF :
1) uthoffs syndome: with multiple sceloris = myelin deteriores in optic and if they are emotional one channels can stop working (knock out)
2) selective adapation: with normal people; measure sentivity overall (CSF) over range of SF and have them adapt to a SF then when you measure again there will be a big chunk missing from the CSF curve because you tired out a SF
70
What are the 2 pathways after the straite cortex?
1) temporal pathway/ventral pathway/WHAT
| 2) parietal pathway/dorsal pathway/WHERE and HOW
71
Ventral pathway and 2 related structures
| - What happens when these 2 structure are dmange?
- temporal lobe
- p-cells (fine detail and color)
a) v4: color perception (damange to here casues cebral achromatopsia: can't see color)
b) inferotemporal cortex (IT): abiity to see and recgnozie shapes (dmanage here causes agnosia: objects; and prosopognisa: faces)
72
Doral pathway and 2 related structures
| - What happens when these 2 strutures are dmanaged?
- pareital loe
- m-cells (motion)
a) medial temporal cortex (MT) (dmanage here causes Atkintopsia: series of still pictures in life)
b) parietal cortex: can experience hemisptal neglect with damange here
73
Hemi-sptail neglect
- fail to notice half of their visual field
- usually from STROKE
- will only draw half of their field and even only half of a stick person's limb
- can't see the fire on the other side of the house but will choose the non-burning side
- can't see the light going on but will point to it when asked to guess
74
What is color most related to?
- wavelength
75
Selective reflectance
- color light is reflected back into your eye
e. g. if you see red it is reflecting red back into your eye
e. g. if you see baclk then all light is absorbed by object and reflects an equal amount of WL back
e. g. white gives you alot of WL back to eye
76
What are the 3 components of color?
1) hue (chroma): most related to WL
2) brightness: related to amplitude
3) saturation: related to purity of color - when mix it beomes desaturated
77
Monochromiatc
- purest color that is not desaturated
- only has 1 WL = pure color is mor rare bc most light we see is mixture of wavelengths
e. g. gray is mixture of black and white
e. g. pink is white and red
78
What did Newton discover?
- newton put sunlight through a pyramid and got a rainbow
- this means that sunlight (white) is a combination of all colors and you can decompose a color anymore- once divided they can' be divded again
79
Young and Helmholtz Trichromatic color theory
- we see 3 different colors because we have 3 different cones
80
Color and according wave lengths
- red = long WL
- green = medium WL
- blue = short WL
81
Describe the color matching experiement
- use to test for color deficicney
| - use mixture of S M L WL to match the pure monochromatic light
82
How do you get white in color matching experiment?
- Red, green and blue at the same intensity = white
83
How do you get yellow?
- mix red and green to get yellow because yellow is inbetween them on the spectrum
84
How does pointalism work?
- E.g. when you hav red and green they fall on the same point in the retina so the eye does the mixing of colors that would otherwise be impossible with paint
85
Subtractive color mixing
- when colors are mixed together they absorb combintation of colors so it reduces the amount of light that is reflected back into your eye
- this is opposite of light that actually increase the number of WL that gets into your eye
86
What is special about the opsin in the 3 color cones?
- the retinal and opsin have different amino acid sequencees in the opsin (this is what casues thephotopigment to absorb some lights better than the others)
87
Name the 3 types of opsin and their corresponding color
1) chorolade/green catching (medium WL)
2) erythrolade/red cating (long WL)
3) cyanolade/blue catching (short WL)
88
We don't have equal number of colors cones. Why? Descirbe what happens?
- We have more red and green than blue because of chromatic abberation: different types of light bend differently when they go through lens
- When red goes though it lands on the focal point of retina
- when green bends it lands close to the retina
- when blue bends is bends through too much infront of the focal point
89
What color is missing in the fovea? What does this mnea?
- Blue is missing = our color perception is contingent on where the colors are in our visual field
90
What is color deficency
- not color blind, just have difficulty with color discrimination
91
Dichromats (color deficicency)
- only make 2 types of cones
- MOST COMMON color deficieny
- sex linked (to X trait)
- most common in white and Africans and least in First Nations
92
3 differnt types of dicrhomats depednding on which color one you can't make: Descirbe what they see
1) Protanope: no red = see blue, yellow and gray neutral point
2) Deuteranopes: no green = see blue and yellow and gray neutral point is different (similar to protanopes)
3) Tritanope: no blue - RAREST = see reds and blue/green with gray point in between
- can distingush between red and green but rouble with blue and yelow
93
How do you determine if someone is color deficient? (2)
1) color matching experiment
| 2) Ishihara color plates
94
Monochromats (2 types)
- see black and white
1) rod monochromatic: don't have cones at all - light is too bright and lack acuity
2) cone monochromatic: can only make 1 color photoreceptor so they don't have another color to compare it too = color bline
95
Anamalous trichromates
- they have 3 cones but don't mix the same as everyone else
| - amino acide sequence for 2 cones are too similar so they have trouble with color matching experiment
96
Tetrachromatics
- humans are now starting to see other colors because they have 4 cones
97
When you have glaucoma and other visual problems what color cone do you loose first?
BLUE
98
Herrings Opponent process theory
- people who can't tell difference between red and gree OR blue and yello but not other combinations because we have color opponnent cells
99
Color opponent cells:
- a results of how cones are wired up
| e. g. if you have a R+/G- cell then the red sends excitatory AP and green sends inhibitory AP
100
What are the 2 colors systems in opponent theory?
- Red and green collate to one cell
| - blue and yellow have an intermediate cell (red and green come together to mix yellow)
101
Does the afterimage become explained by single or double opponent cells?
Single opponent cells
102
Double opponent cells
- are in the blobs of the hyperbolums that specifically look for color contrast = why colors seem so vibrant
103
Color Constancy
ability to see ting sthat are the same color but the quality of light changes
104
Depth perception
- Ability to see how far away things are
- important for motor coordination
- distal stimulation (3d) and proximal (2d) on the retina
105
What is the 1 cue we have in the retina? And what 2 tings does it tell us about?
- is a proximal cue (2d) - visual angle: tells us about 2 things:
1) real size of objects
2) about the depth
106
What are 2 cueds of depth from physiology?
1) ciliary muscles: Squash lens when things are close and stretch it when things are far - use muscle to figure out distance away
2) convergence of eyes: go cross eye when things are closer to us
- LIMITED use of range
107
Extraocular muscles
- use to turn your eye inward to see things closer to you
108
What is a monocular cue?
- only requires 1 eye
109
Relative size familiar size
- you have knowledge about the object e.g. you know that a human cannot be the size of a footbll
110
Occulation
- overlap
| - object closer to you covers the other
111
Height in the field of view
- close you are to the horizon in the sky = farther away
112
Shading
- further away seems darker
113
Linear perspective
- AKA perspective convergence
| - things further away reced in depth
114
Atmospheric perspective
- farther things seem blurrier than things closer
115
Texture gradiant
- Gibson found dept cue that is consistent
| - repeition gets closer together as you move further into depth
