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

Question 1

What is light called?

Answer 1

electromagnetic radiation

Question 2

What is electromagnetic radiation?

Answer 2

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

Question 3

How do rays travel

Answer 3

In straight lines at a constant very high speed

Question 4

In regards to light, what is a particle?

Answer 4

Discrete packets or quanta.

Question 5

What are light particles known as?

Answer 5

Photons

Question 6

What is the wavelength of light measured in?

Answer 6

Nanometres.

Question 7

What is the light spectrum to and from

Answer 7

400-700 nm

Question 8

What is wavelength

Answer 8

How many metres long is this wave

Question 9

What is light intensity?

Answer 9

The intensity of the electromagnetive wave.

Question 10

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

Answer 10

measured in candelas or metres squared

Quantity is known as luminance.

Question 11

What is luminance?

Answer 11

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

Question 12

What is the range of luminances that your vision can see

Answer 12

10000000 luminances

Question 13

What is incident light?

Answer 13

The light you see that is reflected from objects.

Question 14

Why does something look black?

Answer 14

BEcause it doesnt reflect much light.

Question 15

What is contrast

Answer 15

How bright something is against its background

Question 16

When lmax=lmin, what is the contrast?

Answer 16

0

Question 17

What is the cornea?

Answer 17

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

Question 18

What is the pupil

Answer 18

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.

Question 19

What is the lens

Answer 19

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.

Question 20

What is the retina

Answer 20

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

Question 21

What is optic nerve

Answer 21

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

Question 22

What is focusing

Answer 22

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

Question 23

What parts of the eye concentrate of focusing

Answer 23

The cornea and the lens

Question 24

How does the cornea help with focusing

Answer 24

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

Question 25

How does the lens help with focusing

Answer 25

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

Question 26

What is accomodation with lenses

Answer 26

The lens can be stretched to allow focusing of far objects

Question 27

What is emmetropia

Answer 27

Normal refractive condition. appropriate focus

Question 28

What is Myopia

Answer 28

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

Question 29

What is hyperopia/Hypermetropia

Answer 29

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

Question 30

What is Presobyopia

Answer 30

Old age- inability to change accommodation

Question 31

What is Astigmatism

Answer 31

Different focal lengths for different oritentations.

Question 32

What is transduction in vision

Answer 32

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

Question 33

What are photoreceptors

Answer 33

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

Question 34

What do Ganglion cells possess to do with transduction

Answer 34

Long axons that exit the eyeball via the optic nerve

Question 35

What is the blind spot

Answer 35

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

Question 36

What is the fovea/macula

Answer 36

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

Question 37

What is the optic disc

Answer 37

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

Question 38

Where do ganglion cells get their inputs from?

Answer 38

A large amount of rods and cones. (photoreceptors)

Question 39

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

Answer 39

Light falling over a range of locations on the retina.

Question 40

What is the receptive field?

Answer 40

The light that falls over a range that affects the firing

Question 41

Where are your receptive fields small

Answer 41

Where vision is very sharp like in the fovea

Question 42

What is accuity

Answer 42

High resolution

Question 43

What are receptive fields like in the periphery?

Answer 43

Larger and less dense. Blurrier.

Question 44

Where do retinal ganglion cell axons terminate?

Answer 44

In the lateral geniculate nucleus | Structure in thalamus

Question 45

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

Answer 45

Optic chiasm

Question 46

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

Answer 46

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

Question 47

What is partial decussation

Answer 47

When they cross over to opposite sides

Question 48

Where does the LGN project to?

Answer 48

Primary visual cortex in the occipital lobe via optic radiations

Question 49

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

Answer 49

V1

Question 50

What is retinotopic?

Answer 50

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

Question 51

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

Answer 51

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

Question 52

What does the retina ganglion cell receive input from?

Answer 52

Many photoreceptors

Question 53

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

Answer 53

On centre and off centre

Question 54

What is the on centre

Answer 54

One concentric area of a ganglion cell.

Question 55

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

Answer 55

increase in ganglion cell actvity

Question 56

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

Answer 56

decreases ganglion cell activity.

Question 57

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

Answer 57

Causes decrease

Question 58

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

Answer 58

Causes increase

Question 59

What does 0 represent on ganglion cell firing

Answer 59

Baseline or spontaneous

Question 60

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

Answer 60

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

Question 61

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

Answer 61

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

Question 62

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

Answer 62

Would fire at a spontaneous rate