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Perception > Week 4- Light, Eye and Brain, and Spatial Vision > Flashcards

Week 4- Light, Eye and Brain, and Spatial Vision Flashcards

1
Q

What is light called?

A

electromagnetic radiation

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2
Q

What is electromagnetic radiation?

A

A wave of light where there are periodic changes in the electric and magnetic field

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3
Q

How do rays travel

A

In straight lines at a constant very high speed

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4
Q

In regards to light, what is a particle?

A

Discrete packets or quanta.

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5
Q

What are light particles known as?

A

Photons

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6
Q

What is the wavelength of light measured in?

A

Nanometres.

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7
Q

What is the light spectrum to and from

A

400-700 nm

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8
Q

What is wavelength

A

How many metres long is this wave

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9
Q

What is light intensity?

A

The intensity of the electromagnetive wave.

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10
Q

What is the system that takes visibility into account when regarding the intensity of the wave?

A

measured in candelas or metres squared

Quantity is known as luminance.

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11
Q

What is luminance?

A

The intensity of the light that we can see as relevant to human vision

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12
Q

What is the range of luminances that your vision can see

A

10000000 luminances

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13
Q

What is incident light?

A

The light you see that is reflected from objects.

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14
Q

Why does something look black?

A

BEcause it doesnt reflect much light.

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15
Q

What is contrast

A

How bright something is against its background

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16
Q

When lmax=lmin, what is the contrast?

A

0

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17
Q

What is the cornea?

A

The transparent window into the eyeball. Very see through, thin and curved. Does a lot of the focusing that your eye does.

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18
Q

What is the pupil

A

The dark circular opening at the centre of the iris in the eye where light enters the eye
It is a hole and a gap where the iris stops.

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19
Q

What is the lens

A

Enables changing focus using ciliary muscles.
Physical transparent object that changes its shape. When it gets the right shape it focuses the light rays at a single point on your retina and results in sharp vision.

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20
Q

What is the retina

A

A light-sensitive membrane in the back of the eye that contains rods and cones, which receive an image from the lens and send it to the brain through the Optic Nerve

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21
Q

What is optic nerve

A

Where all the axons exit. Take signals up to the higher sense

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22
Q

What is focusing

A

The recombining rays from various directions to form a single point on the imagine surface

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23
Q

What parts of the eye concentrate of focusing

A

The cornea and the lens

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24
Q

How does the cornea help with focusing

A

It is curved so light refracts a constant amount. The cornea has greater refractive power

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25
Q

How does the lens help with focusing

A

Lens refracts light by variable amount. Lens can be stretched to allow focusing of far objects.

26
Q

What is accomodation with lenses

A

The lens can be stretched to allow focusing of far objects

27
Q

What is emmetropia

A

Normal refractive condition. appropriate focus

28
Q

What is Myopia

A

Near or short sightedness. Focal length is too short. Light is focused in front of the retina. Need concave corrective lenses.

29
Q

What is hyperopia/Hypermetropia

A

Focal length is too long, light focused behind retina. Need convex corrective lenses.

30
Q

What is Presobyopia

A

Old age- inability to change accommodation

31
Q

What is Astigmatism

A

Different focal lengths for different oritentations.

32
Q

What is transduction in vision

A

Rods/cones pass electrical impulses to ganglion cells via bipolar/amacrine/horizontal cells

33
Q

What are photoreceptors

A

Rods/cones
Rods are for high sensitivity (night vision)
Cones for lower sensitivity (daytime)

34
Q

What do Ganglion cells possess to do with transduction

A

Long axons that exit the eyeball via the optic nerve

35
Q

What is the blind spot

A

Where the optic nerve leaves the eye and there are no photoreceptors

36
Q

What is the fovea/macula

A

Has many receptors, no blood vessels. Specialised for high detailed vision- photo receptors densely packed.

37
Q

What is the optic disc

A

Ganglion cells axons leaving the eye through the optic nerve. No receptors here

38
Q

Where do ganglion cells get their inputs from?

A

A large amount of rods and cones. (photoreceptors)

39
Q

What could the firing of the ganglion cell be affected by?

A

Light falling over a range of locations on the retina.

40
Q

What is the receptive field?

A

The light that falls over a range that affects the firing

41
Q

Where are your receptive fields small

A

Where vision is very sharp like in the fovea

42
Q

What is accuity

A

High resolution

43
Q

What are receptive fields like in the periphery?

A

Larger and less dense. Blurrier.

44
Q

Where do retinal ganglion cell axons terminate?

A

In the lateral geniculate nucleus

Structure in thalamus

45
Q

Where do the axons cross over on the way to the thalamus?

A

Optic chiasm

46
Q

Where do signals from the left visual field go and vice versa

A

Left visual field go to right lgn (lateral geniculate nucleus)

47
Q

What is partial decussation

A

When they cross over to opposite sides

48
Q

Where does the LGN project to?

A

Primary visual cortex in the occipital lobe via optic radiations

49
Q

What area projects to other important extra-striate brain areas?

A

V1

50
Q

What is retinotopic?

A

Cells next to each other have retinal receptive fields next to each other on the retina.
Each extrastriate Cortical Visual areas is retinotopic except MST

51
Q

What happens to the processing when we move further away from V1?

A

The areas become more selective. Many connections are lateral or backward

52
Q

What does the retina ganglion cell receive input from?

A

Many photoreceptors

53
Q

What are the two types of are in the ganglion cell?

A

On centre and off centre

54
Q

What is the on centre

A

One concentric area of a ganglion cell.

55
Q

With the on centre, what happens when light on inner portion?

A

increase in ganglion cell actvity

56
Q

For on centre, what happens when light on outer portion?

A

decreases ganglion cell activity.

57
Q

For off centre, what happens with light on inner portion?

A

Causes decrease

58
Q

For off centre, what happens with light on outer portion?

A

Causes increase

59
Q

What does 0 represent on ganglion cell firing

A

Baseline or spontaneous

60
Q

What is centre-surround antagonism/ lateral antagonism/ lateral inhibition

A

When there are two zones in a receptive field which operate in two separate ways where one is exictatory and one is inhibitory

61
Q

To make ganglion cells fire as much as they possibly can, the best stimulus would be to …

A

A concentrated area of light just on the excitatory centre and no light in the inhibitory surround

62
Q

What would happen if there was no stimulus on the cell what so ever

A

Would fire at a spontaneous rate

Perception (5 decks)

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