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Neuroscience > Vision > Flashcards

Vision Flashcards

1
Q

photons

A

particles of energy

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2
Q

waves

A

electromagnetic energy

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3
Q

wavelength

A

colour

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4
Q

intensity

A

brightness

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5
Q

what controls the lense?

A

ciliary muscles

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6
Q

what controls the amount of light hitting the retina?

A

irises

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7
Q

where does the light enter through the eye?

A

pupil

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8
Q

adjustment of pupil disparity

A

difference between sensitivity and acuity

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9
Q

more light =

A

small pupil (reducing light - contraction) = depth of focus (higher acuity as light is focused on retina)

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10
Q

less light =

A

dilated pupil (allowing more light - relaxation) = less focus (light dispersed on retina - lower acuity)

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11
Q

adjustment of the lense

A

accommodation

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12
Q

binocular disparity

A

difference in the position of the same object on the two retinas
constructs 3D images from 2D
greater disparity for closer objects
eyes placed side by side on head

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13
Q

5 layers of the retina

A 
retinal gangloin cells
amacrine cells (H - horizontal)
bipolar cells 
horizontal cells (H)
receptors (rods and cones)
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14
Q

what problems does light exiting through the gangloin cells create?

A

blindspot - cant be any receptors where the light exits (retinal gangloin axons exit through the back of the eye)
- completion

distortion - light goes through lots of cells and distorts images
- fovea (high acuity vision)

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15
Q

duplexity theory

A

cones and rods mediate different kinds of vision

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16
Q

photopic vision

A

cones - used in good lighting and provides high acuity COLOUR vision

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17
Q

scotopic vision

A

rods - used in poor lighting when not enough to excite cones

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18
Q

what affects how bright a stimulus looks?

A

wavelength

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19
Q

Purkinjee effect

A

change in brightness of colours as the amount of light hitting the object is between the two spectral sensitivity curves

GREEN & BLUE brighter under DIM illumination

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20
Q

how and why does the eye move?

A

vision is a summation of what we have recently seen
Tremor
Drifts
Saccades (4 per second) - small jerks (visual neurons respond to change)

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21
Q

transuction

A

conversion of one energy source to another

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22
Q

rhodopsin

A

g protein that responds to light - gets bleached

when in light, sodium channels (as they are partially open in the dark) close and hyperpolarise the rods
- this starts a cascade of intracellular events stopping the release of glutamate

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23
Q

retina-geniculate-striate pathways

A

conducts signals from each retina to the primary visual cortex, via the lateral geniculate gyrus

left side of visual field
ipsilaterally (same side) from the temporal hemiretina
or
contralateraly from the inside of the nasal hemiretina which goes across the optic chiasm
then
the pathways go to the lateral geniculate nuclei

24
Q

retinotopic

A

each level of the retina-geniculate-striate pathway is organised like a map of the retina
2 stimuli presented to adjacent areas of the retina excite adjacent neurons at all levels

25
Q

Parvocellular layers

A 
(P) 
top 4 layers of the primary visual cortex
small cell bodies
responsive to colour
fine pattern
stationary or slow moving objects
26
Q

Magnocellular layers

A

(M)
bottom 2 layers of PVC
large cells
sensitive to movement

27
Q

match bonds

A

colour seems less intense next to a darker shade - contrast at edges enhanced

28
Q

contrast enhancement

A

highlights edges

29
Q

lateral inhibition

A

receptor on the lighter side of the edges fire more, dull side less
- research on the horse shoe crab

30
Q

Hubel and Wiesel (2004) - method

A

neural understanding of vision

microelectrode placed near a single neuron
eye movement blocked
receptive field of a neuron is identified
record response of neuron

studies retinal gangloin cells, lateral geniculate neurons, striate neurons from PVC

31
Q

Hubel and Wiesel (2004) - findings

A

4 commonalities
- fovea has smaller receptive field
- all neurons had circular receptive fields
- all neurons were monocular (receptive fields in one eye but not the other)
- some neurons at all levels had receptive fields that had an excitatory and inhibitory area (separated by a circle)
on centre cells and off centre cells

32
Q

simple cells

A

receptive fields that can be divided into off/on regions

unresponsive to diffuse light

all monocular

cortical areas = straight lines
can be circles or rectangles

33
Q

complex cortical cells

A

rectangle receptive fields
respond to straight lines

different in 3 ways:

  • larger receptive field
  • no on/off divide
  • more binocular complex cells
34
Q

organisation of PVC

A

functional vertical columns

location of columns is influenced by the location on the retina of its visual field

neurons with simple preferences synapse onto those with more complex preferences

35
Q

contextual influences

A

depends on the large scene how visual neurons in the cortex respond

36
Q

hues

A

colours

37
Q

black

A

no light

38
Q

grey

A

intense mixture of wavelengths at low intensities

39
Q

white

A

intense mixture at high levels

40
Q

trichromats

A

primates that see in colour (3 cones)

41
Q

dichromats

A

primates that see in 2 (lack red pigment)

42
Q

component processing (trichromatic theory)

A

Young
3 different kinds of colour receptors -
each with a different spectral sensitivity
3 different cones

43
Q

opponent process theory

A

Hering
2 different classes of cells for encoding colour and brightness
1) red - hyperpolarisation, green - hypopolarisation
2) blue and yellow

  • based on the fact that complementary colours cant exist and the after image of one colour is the other
44
Q

visual system

A

combination of the 2
3 different types of cones (blue, green and red)

each has its own absorption spectrum

there are cells that respond to one colour and not the other

45
Q

colour constancy

A

colours stay the same throughout different intensities

Edwin Land - Mondrian - colour is determined by an objects reflectance
as long as red, green and blue light hit it it will look the same

46
Q

dual opponent colour cells

A

‘on’ to one wavelength and ‘off’ to another

concentrated in peglike columns (called blobs)

47
Q

3 types of visual cortex

A

Primary –> Secondary –> Visual association cortex (top)

as you move up the hierarchy the stimuli the cells respond to are more complex and they have larger receptive fields

48
Q

scotoma

A

damage to areas of the PVC produce areas of blindness in the contralateral visual field

49
Q

perimetry test

A

test for scotoma

50
Q

hemianscopic

A

scotoma covering half the eye

51
Q

blindsight

A

displayed by people with scotomas who respond to stimuli in their area of blindness

52
Q

flow of the visual cortex

A

SIMPLE —> COMPLEX

53
Q

dorsal stream

A

where/control of behaviour - neurons respond to spatial stimuli (movement)/affects direct behavioural interaction with objects

what/conscious perception theory - characteristics of objects/mediate the conscious perception of objects

54
Q

prosopagnosia

A

inability to recognise faces

fusiform face area (FFA)

55
Q

akinetopsia

A

inability to see movement

damage to the middle temporal area (MT)

Neuroscience (15 decks)

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