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Pyschology > The Visual System > Flashcards

The Visual System Flashcards

1
Q

how does light affect our perception

A

wavelength and intensity of a light affects COLOUR and BRIGHTNESS

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2
Q

iris

A

donut shaped bands of contraticle tissue that affect the amount of light entering the retina

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3
Q

pupil

A

hole in lens where light enters which adjusts in size to changes in light (sensitivity and acuity)

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4
Q

lens

A

focuses light on retina; adjusted by cillary muscles

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5
Q

sensitivity

A

ability to detect presence of an object in dim light

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6
Q

actuity

A

abilitiy to see details of an object

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7
Q

accomodation

A

adjusting configuration of lenses to bring images into focus on the retina

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8
Q

label an eye diagram

A

x

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9
Q

what have verebrates evolved to have

A

bilateral vision
stereoscopic vision (3D perspection)
bincoular disparity
colour vision

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10
Q

convergence

A

eyes coordinate so poitns in visual world correspond to the retina

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11
Q

binocular disparity

A

difference in position of the same image on 2 retinas

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12
Q

label the cells in the retina

A

x

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13
Q

amacrine and horizontal cells

A

specialized for lateral communication

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14
Q

fovea

A

indentation of ceter of retina for ‘high acuity’ vision

this thin layer dilutes incoming light

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15
Q

blind spot

A

where optic nerve connects= hence no visual processining occurs here

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16
Q

how does the visual system cope with the blindspot

A

visual information by periperhal receports fill in the ‘gaps’ (completion)

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17
Q

types of photoreceports

A

rods and cons

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18
Q

cones

A 
phototrophicv vision
colour perecpetion
high lighting
high actuity
1 cone to 1 bipolar cell
3 types (RGB)
in centre of the retina
few cones converege to each ganglion cell
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19
Q

rods

A 
scotopic vision
sensitive vision (shape/detail, etc)
dim lighting
low acuity
several rods converge to 1 ganglion cell (multiple rods: 1 bipolar cell)
1 type
peripheray of retina
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20
Q

visual perception

A

summation of recent visual information

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21
Q

temporal integration

A

how visual system fills in time-lags during processes

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22
Q

involuntary fixational eye movement

A

eyes are contionusly moving to allow us to see even duraction fixation

this results in tremors, drifts and saccades

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23
Q

visual transduction

A

conversion of one form of energy to another: in terms of visual transduction this referes to the conversion of light to neural signals

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24
Q

how does visual transduction occur

A

rhodopsin absorbs light in visual receptors; this is a G-Protein that responds to LIGHT instead of neurotransmitters which activates chemical events

it acts by INHIBITION

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25
Q

in dark light, rhodopsin… (3 steps)

A
  1. rhodopsin is inactive
  2. sodium channels open
  3. sodium ions flow into rods= slight depolarization of them
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26
Q

in bright light, rhodopsin… (3 steps)

A

1, light reaches rhodopsin

  1. sodium channels close
  2. sodium ions can’t enter= hyperpolarizes rods
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27
Q

after passing through the retina, what happens to visual information

A

it is transported vis the retina-geliculate striate pathways to the primary visual cortex

signals from LEFT visual field are transported to RIGHT primary visual cortex

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28
Q

retina reliculate striate pathways mechansims

A

carry signals from retina to primary visual cortex via the lateral geniculai nuclei in the thalamus using left and right pathways

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29
Q

RGS pathways

A

6 layers; each layer of each nucleus has different input from all the convulaed visual fields on an eye

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30
Q

retinotopic organization

A

RGS is retinotopic as each level is organized as a map in the retina

disproportionate amount of each system is dedicaed to analyzing the fovea

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31
Q

what is an edge

A

perception of a contrast between 1 adjacent areas of a visual field; yields information information about an object

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32
Q

how do we see an edge

A
  1. contrast

2. brightness

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33
Q

mach bands

A

nonexistence stripes of brightness/darkness adjacent to an edge

they enhance the CONTRAST of an edge and allow the nervous system to improve its perception of edges

34
Q

lateral inhibition

A

when a receptor fires= it inhibits its neighbours from using lateral networks

greatest when receptor is MOST illuminated

35
Q

what are the recpetive fields of visual neuron

A

visual fields where a visual stimulus infleunces the firing of a neuron

36
Q

who were Hubel and Wiesel

A

they mapped out the recpetive fields of the visual system to understanding increasing neural respones at different receptor levels

37
Q

Hubel and Wiesel studies (4 steps)

A

did studies on cats/monkeys visual systems:

  1. placed microelextrodes near single neurons
  2. blocked eyemovement by paralyzing eye muscles
  3. receptive fields were identified
  4. the neuron responses were measures by providing stimules where activity was measured
38
Q

commonalities of retinal ganglion cells, lateral geniculate nuclei and lower neurons (4)

A
  1. receptive fields in fovea smaller than in periphera of retina
  2. all neurons have circular receptive fields
  3. all neurons are monocular (specific to one eye)
  4. many neurons have exictatory/inhibitiory areas separated by the ciruclar boundaries
39
Q

on center cells

A

respond to light shone on central region of the receptive field
inhibit when light in peripehary

40
Q

off center cells

A

respond to inhibition when light in center

exicte when light in peripeheray

41
Q

how does light influence neurons

A

turn neuron firing on or off (inhibition or exitaction)

42
Q

Hubel + Wisel on functions of neurons

A

functions of neurons in retina geniculate striate pathways are to respond to the degree of brightness contrast in 2 areas of the receptive fields

43
Q

2 classes of V1 receptive fields

A
  1. simple cortical cells

2. complex cortical cells

44
Q

simpel cortical cells

A
  • unresponsive to difference light
  • receptive fields in ‘on/off’ areas with straight lines
  • all are monocular
45
Q

complex cortical cells

A
  • more numerous
  • rectangular receptive field + straight line stimuli
  • unresponses to difffuse light
  • larger receptive field
  • dont divide into off/off regions
  • cells response/difre contniously to light
  • can be bincoluar
46
Q

Hubel-Wiesel: organization of the V1 (4)

A
  1. organized in functional vertical angles/columns
  2. location of various functional columns influenced by location on retina in dominant eye
  3. columns prefer straight line angels
  4. preferences of neurons become more complex down the visual pathway
47
Q

Two theories of seeing oclour

A
  1. component theory

2. opponent processing theory

48
Q

component theory

A

‘trichromatic’ idea that 3 colour cones each pair with different spectral sensitivies

49
Q

opponent processing theory

A

2 classes of cells encode for colour or orientation;

  1. 3 cells encode for TWO colour perceptions when cones are hyperpolarized (red) or depolarized (green)
  2. second class of cells encode for blue and yellow
50
Q

component theory thinker

A

Young

51
Q

opponent processing theory thinker

A

Herring

52
Q

3 visual cortex classes

A

primary
secondary
visual association

53
Q

primary visual cortex (what and where)

A

recieves input from visual relay nuclei in thalamus

found in posterio region of occipital lobe

54
Q

secondary visual cortex (what and where)

A

recieve input from V1

in prestriate/inferotemporal cortex

55
Q

visual association (what and where)

A

recieve input from V2 and other sensory systems in posterior pareital cortex

56
Q

scotoma

A

an area of blindness resulting from damage to V1: however patients often not aware due to ‘completion’ mechanisms filling in blindsight

57
Q

damage to dorsal stream

A

neurons respond to SPATIAL stimuli (direction and location; WHERE)

58
Q

damage to ventral stream

A

neurons respond to CHARACCTERSITCS of objects; colour, shape

the ‘WHAT’

59
Q

bilateral lesions in ventral stream might cuase…

A

can INTERACT with world but not identify (control of behaviour but not conscious pereception)

60
Q

patients with lesions in dorsal stream might…

A

can IDENTIFY but not interact with world (no control of bheaivour but conscious perception yes)

61
Q

prosopagnosia

A

visual agnosis of faces

62
Q

agnosia

A

failure of recognition

63
Q

akinetopsia

A

inability to see movement progressions due to damage in middle temporal area (V5/Mt5)

affects pereption ofmotion

64
Q

cornea

A

focuses light

65
Q

why is the fovea thinner

A

to allow for light to pass through more precisily

66
Q

organization of the visual system

A
  1. retina
  2. LGN= lateral geniculate nucleus
  3. primary visual cortex in thamalas
  4. secondary areas (v2, v3, etc)
67
Q

what does the occipital lobe process

A

low level proccessing of colour, orientation and shape

68
Q

what does the temporal lobe process

A

high level processing of objects and faces

69
Q

how are sensory systems organized

A
  1. HIERARHICAL
  2. FUNCTIONAL
  3. PARALLEL PROCESSING
70
Q

functional segregation of visual system

A

from photorecepotr to thalamus (lgn) to v1 to v2 to asociation cortex

71
Q

current model of organization

A

not hierarhical but still functionalyl segreated/parallel

72
Q

what are saccades

A

ever 3-4 second rapid eye movement= hence there are distinct moments when our eyes get no informatino that our brain ‘fills in the gaps’

73
Q

what is drift

A

fixational eyemovement when eye slowly hovers/moves around an object

74
Q

what is fixtaion

A

period of time when you reyes is alighed and kept on target to proces information

75
Q

what is the visual field

A

total area at which an object can be seen by your eye

76
Q

what is the visual receptive field

A

portion of a visual system that a neuron responds to; increaes along visual hierarchy

77
Q

what is convergence

A

compression of visual information into an optic nerve by photoreceports (multiple inputs into one output)

78
Q

what do illusions demonstrate

A

our eyes are never still!

79
Q

saccades

A

rapid eye movement as brain is always updating itself and filling in gaps

80
Q

waterfall effect

A

motion ‘after effect’ where comparator neuron percieves motion in opposite direction as it is inhibited and continues moving dowardds

81
Q

what is light

A

waves of electroagnecy energy split into WAVELENGTH (perception of colour) and INTENSITY (perception of brightness)

82
Q

5 layers of neurons in retina

A 
recetpors
horizontal cells
bipolar cells
amacgrine cells
retinal ganglion cells

Pyschology (13 decks)

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