Vision Flashcards
1
Q
what is feature detection
A
sensory neurons detect colour/edges/lines
2
Q
what is the role of the iris
A
regulate amount of light reaching retina
3
Q
what is the role of pupil size
A
regulate sensitivity and acuity
4
Q
what happens when pupils constrict
A
reduced light - increased sensitivity = sharp and great depth
5
Q
what happens when pupils dilate
A
more light enter eye - sacrifice depth and acuity
6
Q
what happens when more light enters the eye
A
image is more blurry and less acuity
7
Q
what is the role of the cornea
A
help focus incoming light
8
Q
what % is the cornea of the eye focusing power
A
75%
9
Q
what is the lens help in place by
A
ligaments called zonules
10
Q
what is the role of the lens
A
bends light to change focal distance
11
Q
what is the process called to bend light to change focal distance
A
accomodation
12
Q
what is the effect of a flatter lens
A
thinner = increased focal distance for distance objects
13
Q
what is the effect of a rounder/thicker lens
A
bends light to reduce focus distance - short distance for sharper objects
14
Q
what is retinography
A
imaging process of a retina
used by opticians
15
Q
define transduction
A
light into neural code
16
Q
what is the centre of the retina
A
macula
17
Q
state characteristics of the macula
A
contains fovea
high concentration of photoreceptor cells
18
Q
what effect occurs on the macula as age increases
A
macula degenerates - loss of central vision
19
Q
what is the role of the fovea
A
site of sharpest vision
20
Q
why does the fovea have sharp vision
A
contains lots of photoreceptor cells
21
Q
what is the role of photoreceptor cells
A
convert light to neural signals
process of transduction
22
Q
what is another name of the blind spot
A
optic disk
23
Q
what is surface interpolation
A
perceived surface and fill in gaps of blind spot
24
Q
what is sclera and its function
A
white of eye
protective tissue layer
25
what percentage of nerve fibres make up the fovea
50%
26
which region of the eye is densely packed with cones
fovea
27
what is the function of the blood vessels at the side of the fovea
reduce distortion of light
28
why is light distorted when it enters the human eye
human retina is inside out hence why black spots occur
29
is light distored in octupus
no because their retina is the right way round
30
what is choroid and its function
tissue between retina and sclera
| provides oxygen and glucose to retina cells
31
what is the reflective tissue in nocturnal animals
tapetum lucidum
32
why does red eye occur from camera flash
flash reflected from blood in choroid
33
how is a blind spot filled
info from receptor is used to fill gap from blind spot
34
state 3 layers which compose the retina
photoreceptors
bipolar cells
retinal ganglion cells
35
state the two types of photoreceptors
rods and cones
36
why do stars seem to disappear at night
few roads in the fovea
37
state the follow characteristics of rods
1. lighting
2. type of vision
3. level of convergence, sensitivity and acuity
```
rods = scotopic
operate in dim lighting
peripheral vision
high levels of convergence
poor acuity
high sensitivity
```
38
what is the term used to describe people with 3 cones
trichomats
39
state the following characteristics of cones
```
cones= phototopic
operate best in good lighting
central vision
poor sensitivity
low convergence
high acuity
```
40
state the 3 types of cones
red
blue
green
41
define phototopic and which type of photoreceptor it links to
phototopic = vision in daylight or bright light
| CONES
42
Define scotopic and which type of photo receptor it links to
scotopic = vision in dim light
| RODS
43
what effect does more photoreceptors have on colour
more photoreceptors means better colour resulting power
44
which type of lighting is rhodosin active in
bright lihght
45
what effect does active rhodosin have
1. cyclic GMP broken down
2. sodium channel close
3. cell becomes hyper polarised
4. glutatmate release decreases
46
what effect occurs when rhodosin is not active in the dark
1. sodium channels open
2. cell becomes depolarised
3. number of rods increase
4. glutamate release increases
47
define deuteranamoly
partial loss of green colour vision
| becomes harder to distinguish between red and green
48
what percentage of men and women experience colour blindness
.5% women
| 8% men
49
define colour blindness
altered sensitivity in cones or absence of cones
50
what is the function of bipolar cells
process input from photoreceptor cells
51
what do interneurons aid bipolar cells to do
allows low level signal processing of input from the photoreceptors
52
describe the process of input and output of info in vision
input to photoreceptors
bipolar cells
retinal ganglion cells
output
53
what is the function of ganglion retinal cells
facilitate detection of edges of images
54
what cells are retinal ganglion cells linked up to
bipolar cells
55
what is the basis for edge detection in retinal ganglion cells
maximise contrast to detect edges
56
what colour does a single photoreceptor detect
greyscale
57
what can 2-3 photoreceptors do
detect the difference between wavelength and intensity
58
where was lateral inhibition first observed
horse shoe crab
59
what is the ommatidia
large visual receptors
60
define lateral inhibition
lateral inhibition is the capacity of an excited neuron to reduce the activity of its neighbors
61
what effect does lateral inhibition cause in mach bands
causes contrast enhancement
62
what is the link between light and firing intensity
amount of firing is proportional to light intensity
63
what effect do sideways projections have as a result of lateral inhibition
inhibit activity of neighbour
64
what is the hermann grid
white spots of light appear when not looking at target zone
65
what causes the effects of the hermann grid
lateral inhibition
66
why do the white squares appear in the hermann grid illusion
white squares appear at intersection when foveated
| surrounded by more active receptor fields
67
what is the process that occurs when eyes foveate
1. light intensity projected to photoreceptors
| 2. retinal ganglion cells pass info on to form output
68
what do horizontal cells do?
inhibit other cells when activated
69
where are on centre cells responsive to light
centre of receptive field
70
in on centre cells what would happen to firing in periphery field
firing in periphery field would be off
| no light in periphery field
71
where are off centre cells response to light
periphery receptive field
72
what is the function of off centre cells
respond with inhibition
73
how do off centre cells maximise contrast
maximise firing between centre and periphery field
| centre surround difference
74
what occurs to neighbours which experience high levels of inhibition
lower levels of firing due to inhibition from neighbours
75
define receptive field
area of visual field where the visual stimulus can influence firing of neuron
76
what kind of influences can the receptive field have on firing of the neuron
increase or decrease firing rate
77
what did hubel and wiesel measure
3 layers of the retina geniculate striate pathway
78
what are the 2 categories of neurons in the receptive field
simple cells and complex cells
79
state characteristics of complex cells in the receptive field
1. role in depth perception
2. rectangualr receptive field
3. binocular
80
what do complex and simple cells respond best to
responsive best to straight line stimuli
81
what type of receptors do simple cells have
antagonistic on and off receptors
82
what type of organisation is the primary visual cortex composed of
corticol organisation made up of functional vertical columns
83
what is needed for scene analysis
higher receptive field properties
84
what is the perceptual binding problem
different stimuli are processed in different corticol areas
85
what does V2 process
shape characteristic
86
what is the function of V3
motion and depth perception
87
what is the function of V4
colour and form perception
88
what is the function of v5
motion perception
89
where does info in the dorsal stream travel to
parietal lobe
90
what type of info travels in the dorsal stream
process spatial locations
91
what type of info and where does the info travel in the ventral system
object identity and scene analysis info travel to temporal lobe
92
define visual agnosia
able to see object but can't define or recognise it
93
what is prosopagnosia
can't recognise faces
94
which brain region is damaged in prosopagnosia
fusiform face area
95
what is visual neglect
people unaware of existence of part of their visual field
96
define blindsight
person is conciously blind but retain visual ability or awareness
97
what is meant by columnar organisation in vision
neural signals flow from simple to complex receptive fields
| specific hierachy
98
what is the horizontal electrode track
orientation of neurons at tip - shift systematically
99
what vision function is the horizontal electrode track linked with
spatial location of receptive field
100
which type of track are V1 neurons linked with
vertical electrode track
101
where is the vertical electrode track grouped in
functional vertical columns
102
define vergence
movement of image further away or closer to eyes
103
what are projections to brain stem nuclei responsible for
responsible for visual reflexes eg. accomodation, vergence and pupil control
104
where does the left visual field project to
right visual cortex
105
where does the retino tectal pathway project to and what does it control
project to superior colliculus to orientate head and eyes
106
what is another name for the superior colliculus
optic tectum
107
what are the neurons in the superior colliculus sensitive to
luminate change
108
what is the role of the retino-geniculate pathway
provide input to identify objects and scene analysis
109
what are parvocellular cells and what are their function
small cell bodies
| responsive to colour and stationary objects
110
what are magnocellular cells and what is their role
large cell bodies
| responsive to luminate change - on off movement
111
which photoreceptor provide input for M and P cells
```
cones = input for P cells
rods = input for M cells
```
112
what is the role of the lateral geniculate nucleus
thalamic relay for M and P channels
113
what is retinotopic mapping proportional with
activity in the retina
114
what is the activity in the retina disporportional to
disproportional to activity in visual cortex
115
what does the right visual field project to
left primary cortex
116
what does contralateral projections mean
projections from left visual field would go to right cortex
117
what type of projections does the temporal hemiretina have
one way = ipsilateral
118
what type of projections does the nasal hemiretina have
contralateral
119
where does info that is projected contralaterally seperate
optic chiasm to superior colliculus and visual cortex
120
state the key findings of hubel and wiesel
1. receptive field is smaller in fovea than periphery
2. receptive field has both excitory and inhibitory area
3. receptive field is circular and monocular
