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Brain and Cognition > Vision > Flashcards

Vision Flashcards

1
Q

what do we see

A

The reflection of electromagnetic waves emitted by the sun; color is the absorption of all wavelenghts exept those

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2
Q

optic nerves from the left and right eye partially cross at the …

A

optic chiasm

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3
Q

rods

A

perception at very low levels of light

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4
Q

cones

A

perception at a lot of light: colors and details

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5
Q

difference rods and cones regarding photons

A

rods can be triggered by a single photon, cones need to absorb more photons

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6
Q

fovea

A

Place on the retina where the image you focus on is projected to.

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7
Q

hoe gaat het signaal vanaf retina naar optic nerve

A

photoreceptors -> 5 other cell layers: bipolar cells - ganglion cells -> via optic nerve that goes through the retina, creating a blind spot

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8
Q

waar zijn de rods en waar zijn de cones veel

A

cones veel bij fovea, rods veel buiten de focea

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9
Q

acuity

A

hoe scherp het is: hoogste bij de fovea, wordt minder hoe verder je er vanaf gaat

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10
Q

je hebt alleen een duidelijk en kleurrijk beeld bij de fovea, de rest is wazig

A

maar dit zie je zelf niet zo!

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11
Q

saccades

A

we constantly redirect our gaze (3/4x per seconde) -> niet random maar to salient events

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12
Q

subcortical visual processing

A

Retina -> optic nerves -> optic chiasm -> optic tracts -> lateral geniculate nucleus (LGN) in thalamus -> optic radiations -> primary visual cortex

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13
Q

LGN 2 components and what do they receive

A
  • parvocellular system: from retinal parvocellular ganglion cells
  • magnocellular system: from retinal magnocellular ganglion cells
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14
Q

parvocellular

A

Small conduction velocity
-
Some are color sensitive
-
80% of retinal ganglion cells

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15
Q

magnocellular

A

large receptive fields
(input from many
-
Fast conduction velocity
-
Info about motion and
depth to visual system
-
No color information
-
10% of retinal ganglion
cells

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16
Q

opbouw van LGN

A

6 - L - P
5 - R - P
5 - L - P
3 - R - P
2 - R - M
1 - L - M

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17
Q

optic radiation

A

axons from the LGN project to the primary visual cortex

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18
Q

retinotopic organization at thalamus and V1

A

Objects that are close to each
other in the visual field (and
hence the retina), are also
represented close to each
other in the primary sensory
cortex.

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19
Q

cortical magnification

A

the size of unit area in the retina =/= visual cortex representation -> fovea neemt veel meer ruimte in beslag.

20
Q

cortical modularity

A

cortical columns in primary sensory areas. (bv: ocular dominance colomns: reageren liever op een oog dan op de andere)

21
Q

receptive field

A

region in the retina that evokes a response in the neuron being measured.

22
Q

a neuron in V1 receives input from multiple LGN cells

A

oke

23
Q

LGN cell gets active when a light shines on it, but immediately inactive when a light shines beside it.

A

oke

24
Q

The further you go in the
visual stream, the more
complex the receptive fields!

A

(simple cells vs complex cells (grandmother cells))

25
Q

dorsal stream

A

where -> motion and spatial, to parietal

26
Q

ventral stream

A

what -> form and color, to temporal

27
Q

ezelsbruggetje voor streams

A

venTral - whaT - Temporal lobe

28
Q

visual processing properties

A

lightness/brightness
color
form
depth
motion

29
Q

Simultaneous lightness/brightness contrast
phenomenon

A

patches have the same luminance but you experience them as different colours.

  • door lateral inhibition: patch with darker background will be perceived as lighter, due to contrast. patch with lighter background will be less active due to lateral inhibition. (light = inhibition of surrounding cells!)
    Maar… dit is niet helemaal zo, want het ligt ook vooral aan onze kennis van de wereld.
    Dus; door de inverse problem: many different sources can produce the image on our retina.
30
Q

3 qualities of color

A
  • hue = color
  • brightness = fel
  • saturation = colourness (grey of meer kleur)
31
Q

verschillende cones

A

3! (short, medium and long wavelengths.)

32
Q

color contrast

A

patches with identical physical properties can be seen as very different colours.

33
Q

color constancy

A

patches with different physical properties can be seen as the same colour

34
Q

which area processes colour

A

V4

35
Q

damage to V4 leads to

A

cerebral achromaoopsia (alles in zwart wit)

36
Q

form

A

perception of line lengths, orientation and intersections

37
Q

Does activity in V1 correspond to the actual
stimulus or the perceived stimulus?

A

No, the activation evoked by the stimulus
corresponded to the subjective experience
of the size, not to the actual size.

38
Q

monocular components

A
  • size and depth relative
  • occlusion
  • motion parallax (ver gaat met je mee, dichtbij gaat er tegenin)
39
Q

binocular component

A

retinal disparity because our eyes are further apart -> creates a different picture

40
Q

binocular rivalry

A

each eye gets a completely different image. but it is not a combination between the two, but a continuous change between the two states!

41
Q

motion

A

processed in area V5 wss

42
Q

aperture problem

A

Many combinations of speed
and direction can give rise to the sequence of
images falling on the retina -> hoe???

43
Q

apparant motion

A

Two static stimuli that are
presented in close succession create a sense of
motion. Known in Gestalt psychology as the phi
phenomenon.

44
Q

motion aftereffect

A

After staring at motion to a
single direction, you can observe motion in the
opposite direction when looking away from the
motion (neural adaptation?)

45
Q

You don’t need visual input to get visual cortex
activity!
Visual imagery of an object suffices to recreate the
activity pattern in the visual cortex that would be
active when seeing the object.

A

bv bij denken aan stoel.

46
Q

retinal ganglion cells

A

in LGN!!! -> parvocellular and magnocellular

47
Q

volgorde outside eye

A

sclera -> choroid -> retina

Brain and Cognition (9 decks)

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