Vision

Question 1

What are the 2 principles of vision?

Answer 1

1. Perception is dynamic - we perceive change
2. we perceive constancies in a changing environment

Question 2

What is the electromagnetic radiation continuum?

Answer 2

• is generated when an atom emits a “particle” called a photon
• the energy of photons determines their wavelength
• different wavelengths give rise to the perception of different colours

Question 3

True or false: the human eye is only capable of detecting light within a narrow range of wavelengths

Answer 3

True

Question 4

What is the effect of a short wavelength?

Answer 4

Ultraviolet light
(Gamma rays, X rays)

Question 5

What is the effect of a long wavelength?

Answer 5

Infrared light
(radar, radio)

Question 6

Where is the Retina positioned in the eye?

Answer 6

Above the line of sight and Fovea at the back of the eye

Question 7

What is Saccades?

Answer 7

Our eyes are constantly moving
- if an image stays stable it disappears on the retina (the photoreceptors stop firing) and the brain fills in the missing spaces

Question 8

Describe the stationary blind spot

Answer 8

We have a stationary blind spot where the optic nerve enters the eye and we are unaware of it

Question 9

What controls the shape of the lens to accommodate near or far targets?

Answer 9

the ciliary muscles

Question 10

To focus on a far target what happens to the lens?

Answer 10

Lens flattens

Question 11

To focus on a near target what happens to the lens?

Answer 11

Lens rounds

Question 12

What are the properties of cones?

Answer 12

• fast dark adaptation
• low dark sensitivity
• “yellow” sensitive
• high acuity

(fovea and periphery)(6 million)

Question 13

What are the properties of Rods?

Answer 13

• slow dark adaptation
• high dark sensitivity
• “green” sensitive
• low acuity

(Mainly peripheral vision) (120 million)

Question 14

What is the Duplex retina theory?

Answer 14

Schultze proposed that the rods and cones form two separate visual fields; Photopic and Scotopic

Question 15

What is the Photopic visual field in the Duplex Retina theory?

Answer 15

Bright light vision via cones

• “day blind” without cones

Question 16

What is the Scotopic visual field in the Duplex Retina theory?

Answer 16

Dim light vision via rods

• “night blind” without rods

Question 17

What cells do Receptor cells synapse with?

Answer 17

Bipolar cells

Question 18

What cells do bipolar cells synapse with?

Answer 18

ganglion cells

Question 19

What do Horizontal cells do?

Answer 19

connect different receptor or bipolar cells

Question 20

What do Amacrine cells do?

Answer 20

connect different bipolar or different ganglion cells

Question 21

What do connecting cells (horizontal and amacrine) allow for?

Answer 21

events at one location to influence events at another

Question 22

On average how many receptors connect to 1 ganglion cell?

Answer 22

126

Question 23

What is the function of ganglion cells?

Answer 23

like a lens on part of the visual field - captures image over an area of the retina - receptive field
- enhance the image in its local area

Question 24

What is the function of receptors?

Answer 24

points of light

Question 25

What is the process of lateral inhibition?

Answer 25

- attached receptor cell when stimulated caused rapid rate firing (large response) from ganglion cells - in stimulating an adjoining receptor which did not itself excite the monitored ganglion cell, output of the ganglion cell was reduced - RICH GETS RICHER SCHEME

Question 26

What are the two types of connections that ganglion cells have within their receptive field?

Answer 26

excitatory and inhibitory

Question 27

What is an excitatory connection that ganglion cells have within their receptive field?

Answer 27

Some ganglion cells can be excited by light inside the receptive field

Question 28

What is an inhibitory connection that ganglion cells have within their receptive field?

Answer 28

Inhibited by light outside the receptive field

Question 29

What occurs in centre-surround receptive fields?

Answer 29

illumination of center is inhibitory while illumination of the surround is excitatory

Question 30

In centre-surround receptive fields, what occurs in relation to retinal ganglion cells?

Answer 30

The retinal ganglions cells can act as edge detectors, integrate patterns of lightness over an area and Indicate whether that pattern of lightness within an area is different to that in an adjacent area (an edge)

Question 31

What cells do exhibit centre-surround antagonism?

Answer 31

X cells or Y cells

Question 32

What cells do not exhibit centre-surround antagonism?

Answer 32

W cells

Question 33

What two visual channels are the X and Y cells associated with?

Answer 33

Pravocellular and magnocellular systems

Question 34

What are the characteristics of the Parvocellular system? (size, response, RF size, RF type, RF distribution, movement, speed of nerve, transmission, function)

Answer 34

Size: small Response: sustained RF size: small RF Types: X RF distribution: foveal Movement: poor Speed of nerve: slow Transmission: detail Function: space and colour

Question 35

What are the characteristics of the Magnocellular system? (size, response, RF size, RF type, RF distribution, movement, speed of nerve, transmission, function)

Answer 35

Size: large Response: transient RF size: large RF Types: Y RF distribution: peripherial Movement: good Speed of nerve: fast Transmission: motion Function: depth and time

Question 36

What is the function of the Tectopulvinar system?

Answer 36

- localisation of objects in space - guidance of eye movements - gross pattern perception Some optic tract fibres project to the superior colliculi and then on to the pulvinar and lateral posterior nuclei.

Question 37

What does a Lateral Geniculate Nucleus do?

Answer 37

receive input from the visual cortex (back projections) allowing feedback based on previously processed information

Question 38

What are the structures located in the thalamic region called?

Answer 38

The Tectum

Question 39

Cells in the superior colliculi have receptive fields on the retina and receive their input from...

Answer 39

magno (or magno-like) retinal ganglion cells

Question 40

Without a Lateral Geniculate Nucleus, what occurs?

Answer 40

patterns are unable to be recognised

Question 41

Without the superior colliculi, what occurs?

Answer 41

able to recognise patterns but unable to accurately approach them

Question 42

What are the two seperarte pathways in the Tectopulvinar System and what do they do?

Answer 42

Focal system for recognition Ambient system for localisation

Question 43

What is Blindsight? (Weiskrantz, 1977, 1992)

Answer 43

some people with damage to the focal system can still react to visual stimuli (e.g. point to them) although they claim that they cannot see them

Question 44

How does the Lateral Geniculate Nucleus project?

Answer 44

project to the primary visual cortex in the occipital lobe at the rear of the brain

Question 45

Describe where the lobes and pathways of the visual cortex are positioned in the brain?

Answer 45

The parietal lobe is at the top rear The where pathway is below the parietal lobe extending from the primary visual cortex The occipital lobe is below the where pathway at the rear The Primary Visual Cortex is at the bottom rear of the brain The what pathway extend from the PVC towards the temporal lobe The temporal lobe is at the bottom of the brain towards at the front of the bottom section of the brain (before the dip)

Question 46

What do the simple cortical cells respond to?

Answer 46

bars of a particular orientation

Question 47

What do the complex cortical cells often respond to?

Answer 47

a correctly oriented bar moving across the entire receptive field. Some cells are even direction sensitive

Question 48

What do Hypercomplex cortical cells fire to?

Answer 48

only to moving lines of a particular length or moving corners or angles.

Question 49

What do cortical cells act as?

Answer 49

feature detectors

Question 50

What is the dorsal pathway?

Answer 50

Where - travels up to the parietal lobe and is concerned with motion perception and spatial awareness

Question 51

What is the ventral system?

Answer 51

What - travels to the temporal lobe and is concerned with object recognition

Question 52

Describe how adaptation occurs in the visual system.

Answer 52

the system slowly stops responding to constant stimuli stopping a stimulus can result in an aftereffect (e.g. colour or motion aftereffect) adapting to constant stimulation helps the system stabalise