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Tri 1 2007PSY Week 6 Onwards > Week 7 > Flashcards

Week 7 Flashcards

1
Q

What is sensation

A

involves cells of the nervous system that are specialised to detect stimuli from the environment.

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2
Q

What is perception

A

is the conscious experience and interpretation of information from the senses

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3
Q

What is visible light

A

Visible light is a narrow band of the spectrum of electromagnetic radiation that receptor cells in our eyes detect

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4
Q

What are the 3 dimensions determining the perceived colour of the light

A
  1. Hue = Dominant wavelength
  2. Saturation = Purity
  3. Brightness = Intensity
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5
Q

What is Hue

A

Colour = dominant wavelength at a given moment

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6
Q

What is saturation

A

Is the relative purity of the light being perceived

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7
Q

What is brightness

A

Brightness is the intensity of the electromagnetic energy

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8
Q

What are sensory receptors

A

specialized neurons that detect a particular category of physical events (e.g., light)

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9
Q

What is sensory transduction

A

the process by which sensory stimuli are transformed into changes in the cell’s membrane potential

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10
Q

What are receptor potentials

A

electrical changes produced by a receptor cell in response to a physical stimulus

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11
Q

What is the retina

A

Located at the back of the eye.

An image must be focused on the retina for us to see because receptor cells for vision are located there.

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12
Q

What are photoreceptors

A

Rods and Cones

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13
Q

What is the optic nerve

A

When an image is focused on the retina, this causes changes in the electrical activity of millions of photoreceptors.

This results in messages being sent through the optic nerve to the rest of the brain for further processing.

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14
Q

How are the eyes held in place

A

The six extraocular muscles which are attached to the sclera (tough, white outer coat of the eye).

The sclera is opaque and does not let light in

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15
Q

What is the cornea

A

The cornea is the transparent outer layer at the front of the eye that lets light in to reach the retina

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16
Q

How is the amount of light that enters the eye regulated

A

The amount of light that enters the eye is regulated by the size of the pupil, which is an opening in the iris, the pigmented ring of muscles behind the cornea.

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17
Q

What is the lens

A

The lens is right behind the iris and consists of a series of transparent, onion-like layers.

The shape of the lens can be altered by contraction of the muscles called the ciliary muscles.

Changes in lens shape permit accommodation

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18
Q

Explain accommodation

A

Accommodation refers to the ability of the eye to focus images of near or distant objects on the retina.

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19
Q

What are the 3 main cellular layers of the retina

A

Photoreceptive layer
Bipolar cell layer
Ganglion cell layer

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20
Q

What is in the photoreceptive layer

A

92 million rods and 4.6 million cones

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21
Q

What is inside the fovea

A

It is the central region of the retina and contains only cones

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22
Q

Explain cones

A

Most prevalent in the central retina, found in the fovea.

Sensitive to moderate to high levels of light

Provide information about Hue

Provide excellent acuity

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23
Q

Explain rods

A

Most prevalent in the peripheral retina, not found in the fovea.

Sensitive to low levels of light

Provide only monochromatic information

Provide poor acuity

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24
Q

Why does the blind spot occur

A

because of the optic disc

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25
Q

Explain the optic disk

A

The optic disk is where the axons conveying visual information gather together and leave the eye through the optic nerve = no photoreceptors there to detect light.

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26
Q

Explain bipolar cells

A

Photoreceptors form synapses with bipolar cells.

Bipolar cells form synapses with ganglion cells whose axons travel through the optic nerves (second cranial nerves)

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27
Q

Explain transduction

A

Transduction is the process by which energy from the environment is converted to a change in membrane potential in a neuron

First step in the chain of events that eventually leads to visual perception

28
Q

Explain Photopigments

A

Photopigments are a special chemical responsible for the transduction of visual information embedded in photoreceptors

Photopigment molecules contain a protein (opsin) and a lipid (retinal)

They are embedded into thin plates of membrane that make up the outer segment of photoreceptors (rods and cones)

When a photopigment is exposed to light, it breaks into two parts (protein and lipid).

Splitting triggers a chain of intracellular events to occur that hyperpolarize the photoreceptor membrane

29
Q

What is the receptive field

A

The receptive field of a neuron individual system is the part of the visual field that an individual cell sees. That is the place in which a visual stimulus must be located to produce a response in the cell

30
Q

How many ganglion cells and photoreceptors are in the fovea

A

Approximately equal numbers

31
Q

Because a single cell processes information from many receptors in the periphery, vision is less precise

A

= lower visual acuity

32
Q

because peripheral vision is blurry, we usually want like to project onto the fovea for detailed processing of relevant information

A

= higher visual acuity

33
Q

What are the 3 types of eye movements and explain them

A
  1. Vergence movements (focal point moving towards and away causing outward and inward eye movmements)
  2. Saccadic movements (rapid eye movements, scanning)
  3. Pursuit movements (slower eye movements, more smooth, following something)
34
Q

Explain the optic nerve

A
  • The optic nerves are one type of cranial nerve. The optic nerves carry information from the eyes to the brain.
    • At the back of each eye, the axons of ganglion cells bundle together to form the optic nerve
    • The optic nerve conveys information from the retina to a section of the thalamus called the dorsal lateral geniculate nucleus (LGN)
35
Q

What is the optic chiasm

A

Optic nerves join together at base of brain to form the X-shaped optic chiasm

(where stuff crosses to other side of the brain)

36
Q

What are the 4 steps in the visual pathway

A
  1. Vision begins in the photoreceptors of retina
    1. Next, information from the photoreceptors is sent to rest of brain via optic nerves to lateral geniculate nucleus (LGN)
    2. Neurons in the LGN send axons to the primary visual cortex (sometimes called V1/striate cortex).
    3. From V1, information sent to the visual primary visual cortex (sometimes called V2/extrastriata cortex), and additional cortical areas called V3, V4, and V5
37
Q

What is the LGN

A

Lateral geniculate nucleus.

Located in the thalamus and has 6 layers of neurons inside it.

38
Q

Explain the 6 layers of neurons in the LGN

A

Three layers receive input from ganglion cells of the contralateral eye

Three layers, receive input from ipsilateral eye

Magnocellular layers: two inner layers
Parvocellular layers: four outer layers
Koniocellular sublayers: beneath other two types

39
Q

What is dyslexia related to

A

Magnocellular mediated visual processing

40
Q

Explain the Striate (Primary) Visual Cortex

A

After processing in the LGN, nerve fibres travel to the primary visual cortex, which we also sometimes call the striate cortex, or V1.

The striate cortex is the first cortical region involved in combining information from several sources. It also does some additional processing of the information transmitted from the retinas, before transmitting the information of the visual association cortex (extrastriata cortex).

41
Q

Explain blindsight

A

When the striate cortex is damaged, individuals might experience blindsight. Those with blindsight have a conscious experience of being blind, but subconsciously show some signs of visual processing.

42
Q

Explain the Extrastriate Cortex (visual association cortex)

A

It combines pieces of visual information from the striate cortex to perceive objects and entire visual scenes.

The extrastriate cortex consists of several regions (labelled V2-V5), each which have individual maps of the visual field.

43
Q

Explain the hierarchy of the regions within the extrastriate cortex

A

V1 receives information from “lower” regions

Passes information to “higher” regions (e.g., V2 to V3)

44
Q

What are the 2 main pathways in the hierarchy

A

Dorsal stream (where) Processes where object is located; speed and direction of movement

Ventral stream (what) Processes what an object is and it’s colours.

45
Q

What are the two theories of how colour vision can be explained

A

Trichromatic theory

Opponent Colour system theory

46
Q

Explain trichromatic theory

A

It argues that the eye detects different colours because it contains 3 cones, each sensitive to a single hue.

Photoreceptors have photopigments that have different absorption characteristics.

Absorption is determined by the protein (opsin) in the photopigment

47
Q

What is Protanopia

A

Confuse red and green and see the world in shades of blue and yellow

Normal visual acuity

Red cones are filled with green cone protein (opsin)

48
Q

What is Deuteranopia

A

Confuse red and green

Normal visual acuity

Green cones are filled with red cone protein.

49
Q

What is tritanopia

A

Sees the world in greens and reds

Retina lacks blue cones

Normal visual acuity

50
Q

What is monochromatic vision

A

Does not perceive different hues

Retina lacks all 3 cones

51
Q

Explain Opponent Colour System theory

A

ganglion cells use an opponent colour system with neurons responding to pairs of primary colours.

52
Q

Explain the receptive field of ganglion cells.

A

When a portion of the receptive field is illuminated with the colour shown, the cell’s rate of firing increases. When a portion is illuminated with the complementary colour, the cell’s rate of firing decreases.

- The response characteristics of retinal ganglion cells to light of different wavelengths are determined by the particular circuits that connect the three types of cones with the two types of ganglion cells.
53
Q

What happens after retinal processing

A

Colour information is then sent to the visual cortex via the LGN.

The parvocellular division of the LGN receives information from red and green cones.

The koniocellular division receives information from blue cones.

The magnocellular division is not involved in colour processing.

Next, colour information from the parvocellular and koniocellular systems is conveyed along the ventral stream to the inferior temporal lobe, which is responsible for processing what an object is (including its colour). The ventral stream also receives magnocellular input.

In contrast, the dorsal stream receives mostly magnocellular input (and is not as directly involved in colour processing).

54
Q

What is cerebral achronomatopsia

A

Experiencing colour blindness following brain damage to specific regions of the extrastriate cortex.

World is black and white.

55
Q

What is visual agnosia

A

Unable to identify common items by sight although visual acuity remains.

Thought to be caused by damage to parts of the ventral stream of the extrastriate cortex

56
Q

What does the Lateral Occipital Cortex (LOC) do?

A

It is a region of the extrastriate and it appears to respond to a wide variety of objects and shapes.

57
Q

Explain Prosopagnosia

A

Inability to recognise faces.

Acquired Prosopagnosia is from brain damage

Congenital Prosopagnosia is with birth

Research suggests that the anterior fusiform gyrus is smaller in the people with congenital prosopagnosia.

58
Q

What is monocular depth perception

A

We can perceive depth using one eye

59
Q

What is binocular depth perception

A

We get our most vivid depth perception from binocular information.

60
Q

What are disparity sensitive neurons

A

Disparity sensitive neurons are found throughout the striate and extrastriate cortex.

- Those found in the dorsal stream are involved in spatial perception and respond to large, extended visual surfaces
- Those found in the ventral stream are involved in object perception and respond to the contours of 3D objects
61
Q

Explain the parietal lobe and spatial lcoation

A

The parietal lobe is partly involved in the perception of spatial location and somatosensory perception.

Damage to the parietal lobes disrupts performance on a variety of tasks that require perceiving and remembering the locations of objects and controlling movements of the eyes and the limbs

62
Q

Explain the perception of orientation and the Striate Cortex

A

Most neurons in the striate cortex (primary visual cortex) are sensitive to orientation. That means that the neurons in the primary visual cortex will respond best when a line is in a particular position (e.g., vertical, horizontal).

63
Q

What is the neuron firing rate when a stimulus is vertical and then horizontal

A

The neuron is sensitive to lines oriented vertically. When a horizontal line is shown, the cell does not fire, however, as the line is rotated closer to vertical, it begins to fire more.

64
Q

Explain perception of movement and the extrastriate cortex

A

Area V5/MT of the extrastriate contains neurons that respond to movement

Receives input directly from the striate cortex and other areas of the extrastriate,

Also receives input from superior colliculus (involved in reflexes and eye movements)

65
Q

Explain Area MST

A

Adjacent from V5
Responds to complex patterns of movement
Dorsolateral MST helps analyse optic flow

66
Q

What does bilateral damage to V5 result in

A

Akinetopsia (motion blindness)

Tri 1 2007PSY Week 6 Onwards (4 decks)

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