Vision Flashcards
(102 cards)
1
Q
Discuss sensation vs perception
A
Sensation: Involves cells of the NS that are sensitive to their environment
Perception: the conscious experience and interpretation of information
2
Q
Hue?
A
- Wavelength of light
- What we perceive as colour
- Determined by length
3
Q
Brightness?
A
- Intensity of light
- Determined by amplitude
4
Q
Saturation?
A
-Relative purity of light
5
Q
Electromagnetic spectrum of visible light?
A
400-700 nm, from blue (higher energy, shorter wavelength to red, lower energy and larger wavelength)
6
Q
How is information from SR in the eye transmitted to the brain?
A
Through sensory transduction
7
Q
How do we see?
A
By focusing an image on our retina, helped by the extraocular muscles attached to eyes
8
Q
What regulates the amount of light entering our eyes?
A
Iris
9
Q
What focuses the entrance of light into the eye?
A
The Cornea
10
Q
What are the 3 celllular layers of the retina?
A
- Photoreceptors (cones/rods)
- Bipolar
- Ganglion
11
Q
What is the fovea? Where is it located? what does it allow for?
A
- Region of the retina which allows for the most acuity of vision as it exposes cones only (other layers pushed away)
- Allows for better acuity and colour processing
12
Q
(T/F) there are more cones than rods in the retina
A
F, there are more rods
13
Q
What is the optic disk?
A
Place in the retina where there are no PR, therefore the blind spot
14
Q
Discuss 4 key characteristics of cones
A
- Most prevalent in the central retina (fovea)
- Sensitive to mod/high light
- Provide info about hue
- Provide acuity
15
Q
Discuss 4 key characteristics of rods
A
- Most prevalent in the peripheral retina, NOT found on the fovea
- Sensitive to low levels of light
- Provide monochromatic information only
- Provides poor acuity
16
Q
What are the two other cells in the retina layers?
A
- Horizontal cells
- Amacrine cells
17
Q
Discuss horizontal cells
A
Connect adjacent PR and the neuroprocesses of bipolar cells
18
Q
Discuss amacrine cells
A
Connected to ganglion cells and the neuro processes of bipolar cells, transmitting information from BP –> GC cells
19
Q
Name the two theories of perception of colour in the retina
A
1) Trichromatic coding
2) Opponent-Process coding
20
Q
Discuss trichromatic coding in the retina
A
In TC, the eye will detect different colours b/c it contains three different types of receptors.
21
Q
What are the three types of receptors in TC?
A
1) Short wave CR=blue
2) Medium wave CR=green 3) large wave CR= Red
- All of these are opsin receptors
22
Q
If there is a defect in the CR, according to TC, what are the three types of genetic defects of colour? (PDMT)
A
- Protanopia
- Deutranopia
- Tritanopia
- Monochromatic vision
23
Q
What is protanopia?
A
Difficulty seeing red, red cones filled with green opsin
24
Q
What is deuteranopia?
A
Difficulty seeing green, green cones filled with red opsin
25
What is tritanopia?
Difficulty seeing blue, blue cones are lacking completely
26
T/F in tritanopia, people have difficulty seeing blue b/c their blue cones are full of yellow opsin
F, their blue cones are lacking completely
27
What is monochomatic vision?
All three cones (blue, red and green) are defective
28
What happens when their is a summation of activity when blue, red and green PR are activated?
Summation produces the perception of white colour
29
In opponent-processing coding, which neurons are most considered?
Receptive fields of colour-sensitive ganglion cells
30
Discuss the OPC
Neurons will respond to opposing pairs of primary colours, where the retina contains two kinds of colour sensitive ganglion cells (Red-green and yellow-blue), this may explain why we never see "reddish-green)
-When the receptor is illuminated with a complementary colour (i.e. green), it will decrease the cells firing of its complementary colour (i.e. red), whereas blue and yellow are untouched, which is why we could see blueish green and yellow-ish green (only red is shut off)
31
In OCP, discuss what happens when red light stimulates a red cone
- Red cones transmit an EPSP to the R/G ganglion cells
| - R/G ganglion cells are red when ON, and green when OFF
32
R/G ganglion cells are ___ when ON, and ___ when OFF
Red
| Green
33
In OCP, discus what happens when green light hits a green cone
- Green cone transmits an IPSP to the R/G ganglion cells
| - R/G ganglion is red when ON and green when OFF
34
In OCP, what happens when yellow light hits the retina?
- Stimulates the red and green cones equally
- Red cone sends EPSP to R/G ganglion and Y/B ganglion
- Green sends EPSP to Y/B ganglions and IPSP to R/B ganglion
- The G/R ganglion is cancelled out, and the Y/B ganglion is excited, thus turns yellow
35
The Y/B ganglion is ___ when ON and ____ when OFF
Yellow
| Blue
36
In OCP, what happens when blue light stimulates a blue cone?
- Blue light sends an IPSP to the Y/B ganglion, is inhibited and becomes blue
- Y/B ganglion is ON when yellow, and OFF when blue
37
What happens when the yellow cone is stimulated in OCP?
There are no yellow cones, only red, blue and green. Yellow light is from the red/green cones signalling two different types of ganglions
38
What is the first step in visual perception?
- Converting the external stimulus to internal stimulus
| - Where photopigments are responsible for the transduction of this light energy and change in membrane potential
39
What is the receptive field? Where is it located?
- The visual stimulus must be located in the receptive field to produce a response in the neuron
- Location depends on the location of photoreceptors
40
In the receptive field, what are the two main areas of photoreceptors?
- Fovea (has less PR, lots of cones and smaller receptive field) --> Central vision
- Periphery has more PR, but less acuity --> Peripheral vision
41
What type of ganglion cell are located in the receptive fields to produce central/peripheral vision?
-ON/OFF ganglion cells
42
In C/P vision, when will an ON GC fire the most strongly?
When light hits the centre of it's field
43
In C/P vision, when will an OFF GC fire the most strongly?
When light hits it's surround area
44
In an OFF cell, what happends when light hits both it's on/off areas?
It will cancel eachother out, and produce a baseline pulse
45
What happens when the surround area of an OFF cell is covered in 1/3 darkness, but the centre is still receiving light?
Will decr. the firing rate at the surround area is receiving less light, will not amplify as the centre is still illuminated (dampning the signal)
46
What will happen when the surround area of an OFF cell is covered in 2/3 darkness, INCLUDING the centre?
Cell output will greatly increase, as the centre is no longer opposing the firing,
47
What happens when the entire OFF cell is covered in darkness?
Cell output will return to a similar baseline, as there is still some firing as the centre is muted but there is less light to "activate" the surround
48
Discuss the influence of contrast on GC cells
If a grey square is surrounded by white, it will look darker but if it is surrounded with black it will look lighter On the black background, cells would fire more, on the white background, cells would fire less
49
The center receptive fields will emphasize __
Black/white edging
50
(T/F) In Fovea acuity, there is a 1:1:1 ratio of PR:BPC:GC
T, this allows for increased acuity (everything picked up is transmitted)
51
(T/F) In the periphery acuity, there is also a 1:1:1 ratio of PR:BPC:GC
F, there is a 6:4:1 ratio, as there is less acuity in the periphery
52
(T/F) there are more PR in the fovea, as the ratio is higher
F, there are LESS PR in the fovea, and the ratio is lower (less is more)
53
What is the first synaptic relay from the optic nerve?
To the dorsal lateral geniculate nucleus (LGN), passing through the optic chiasm ("splitting" of the input)
54
Discuss the visual field
The visual field of the L eye overlaps with that of the right eye, this allows us to see the "big picture".
- Then, the information from the L and R are transmitted thru the optic nerve
- The optic nerve is wired to "split" to the opposite sides of the brain thru the optic chiasm
- Then, the information from the L eye reaches the R LGN, the R eye reaches the L LGN, and is then interpreted in the primary visual cortex on either side
55
What is the general path of the visual pathway?
1) Lateral General Nucleus
2) Striate Cortex
3) Extrastriate Cortex
56
Discuss what happens once the AP reaches the LGN
Sends output to VI (primary visual cortex) and V2 ( Visual association cortex)
57
What are the three layers of the LGN? How many individual layers are their in total? (PMK)
- Parvocellular (4 outer)
- Magnocellular (2 inner)
- Koniocellular
- 6 in total
58
In the LGN, the first two layers are closest to the _____
Inside of the brain, these are the magnocellular layers (labelled layers 1.2)
59
What is the striate cortex?
- The first cortical region involved in combining visual information from several sources
- Receives information from LGN, and transmits info to the ES cortex
60
How many layers in the SC?
6
61
What do layers II, III and IVB project to in the SC?
To other cortical areas
62
What do layer V cells project to in the SC?
The superior colliculus and pons
63
What do layer VI cells project in the SC?
Back to the LGN
64
What are the two layers in the SC involved in colour perception?
The paravocellular layer and koniocellular system
65
In the SC, what does the paravocellular layer receive in terms of colour perception?
-Receives information only from red/green cones
66
In the SC, what does the koniocellular system receive in terms of colour reception?
Will receive information from blue cones onlt
67
What does the striate cortex do besides colour perception?
Helps with orientation and perception, where most neurons in the SC are sensitive to orientation
68
How are neurons in the SC sensitive to orientation/perception?
Will only respond when lines are in a particular position, such as at a 90 degree angle
69
What are the three types of orientation-sensitive neurons in the SC?
1) Simple
2) Complex
3) Hypercomplex
70
Discuss the simple orientation-sensitive neurons in the SC
These cells have well defined inhibitory and excitatory regions, which when the line fits into either, it is turned on/off
71
Discuss the complex orientation-sensitive neurons in the SC
Complex cells will be excited by all types of stimulus, inhib/excit regions are more arbitrary and there are so seperate on/off regions
72
Discuss the hypercomplex orientation-sensitive neurons
inhibitory flanks on the ends of the receptive field, so that response increases with increasing bar length up to some limit, but then as the bar is made longer the response is inhibited.
73
What is direction sensitivity?
Cells in the SC will respond to orientated lines/bars/edges moving in a preferred direction, but not in an opposing direction
74
What is the extrastriate cortex responsible for?
- Combining the information from the straite cortex to allow an indiviudual to perceive objects and entire visual scenes
- Received info from lower regions and passes info to higher regions
75
What are the two pathways of the ES?
1) Dorsal stream
| 2) Ventral stream
76
What does the Dorsal stream process?
Where the object is located, including the speed and direction of movement (the WHERE)
77
What does the ventral stream process?
What an object is and it's colours (the WHAT)
78
Which cells in the ES are involved n colour perception?
- Parvocellular system
| - Koniocellular system
79
Discuss the parvocellular system and colour perception in the ES
-Shows high spatial resolution and low temporal resolutio
80
Discuss the koniocellular system and colour perception in the ES
Does not provide information about fine details
81
Discuss the magnocellular system and colour perception in the ES
Are colour blind
82
(T/F) the dorsal stream receives mostly magnocellular input (light/dark contrast and movement)
True
83
(TF) the ventral strea receives equal input from magnocellular, parvocellular and konicellular systems
T
84
Parvocellular are ____ and ____ cones, Magnocellular are _____ and Koniocellular are ____ cones
- Red, green
- Colour blind
- Blue
85
Which stream of the EC is more associated with perception of form? Where does the perception of form begin?
- Relayed to the subregions of the visual association cortex that constitute the ventral stream
- It begin with the neurons that are in the SC senstitive to orientation and spatial frequencey
86
What is visual agnosia?
-When there is damage to the EC, unable to identify common items by sight, although visual acuity remains
87
What is a common symptom of visual agnosia?
prosopagnosia
| -causes when the fusiform face area (FFA) which is devoted to facial recognition is altered
88
The fusiform face area of the brain is most asociaated with the recognition of _____
Faces
89
The extrastriate body area of the brain is most associated with the recognition of ____ and _____
Headless bodies and body parts
90
What are the two types of vision which make up perception?
- Monocular vision
| - Binocular vision
91
Discuss monocular vision
-Allows for perspectives, relies on relative retinal size and there is a loss of detail through the effects of atmospheric haze and appearance of movement
92
What explains why we can see things further away, but with less details (i.e. rail road tracks rolling over a hill)
Monocular vision
93
Discuss binocular vision
Vivid perception of depth thru the process of stereopsis
94
What types of neurons are found in the SC? What do they mostly respond to?
- Binocular vision neurons
| - Retinal disparity
95
Where are disparity sensitive neurons found? What are they associated with
- Found in the dorsal stream (the where)
| - Binocular vision
96
What are the two areas of the brain in the EC are that associated with the perception of movement?
- Area v5 (MV)
| - Area MST
97
Discuss Area v5 in the EC
-Contains neurons that respond to movement, where information is received from the SC and the superior colliculs
98
Discuss the Area MST in the EC
Receive information about movement from V5, and helps analyze optic flow
99
What will happen if there is bilateral damage to the V5?
Inability to perceive movement, known as akinetopsia
100
(T/F) The MT/MST are located in the ventral stream
F, located in the dorsal stream
101
What is found in the ventral stream?
LOC (lateral occipital complex) and FFA (Fusiform face area)
102
Wha is LOC and FFA associated with? Where are they found?
- Object and facial recognition
| - In the ventral stream (the WHAT)
