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Biopsychology > Section 4 > Flashcards

Section 4 Flashcards

Visual System

1
Q

Human vision is limited as we can only see between

A

380 - 760 nm

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2
Q

Do we need light to see?

A

Yes. Not even nocturnal animals can see in the dark we all need some light to see

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3
Q

Visual field (definition)

A

the amount of space that is divided by the nose

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4
Q

Visual sensitivity

A

the neurons ability to detect

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5
Q

Visual acuity

A

refers to detail/resolution

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6
Q

Visual transduction

A

conversion of light energy to neural signals done by the receptors

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7
Q

What is the advantage of having one eye on each side of the head?

A

Larger visual field

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8
Q

What is the advantage of having both eyes in the front?

A

More visual acuity

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9
Q

Binocular disparity (definition)

A

the difference between two retinal images helps create 3D or depth perception - needed by animals who work with tools

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10
Q

Retina (definition)

A

has the receptors that regulate the transduction of light

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11
Q

The two unique spots of the retina are

A

fovea - 90% of receptors here
blind spot - no receptors

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12
Q

The layers of the retina (5)

A

photoreceptors (cones and rods) - transduction & synapse with bipolar cells
horizontal cells
bipolar cells - synapse with retinal ganglion cells
amacrine cells
retinal ganglion cells

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13
Q

Why is the blind spot of the retina “blind”

A

no photoreceptors are found in this part of the retina

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14
Q

Two types of photoreceptors and their properties

A

Cones:
- photopic vision
- predominant in bright lighting
- high acuity
- located in the center of retina

Rods:
- scotopic vision
- predominant in dim lighting
- high sensitivity
- located in the periphery/outer part of the retina

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15
Q

Convergence ratio of cone-fed circuits

A

low convergence 1 cone: 1 bipolar: 1 retinol ganglion
high acuity and low sensitivity

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16
Q

Convergence ratio of rod-fed circuits

A

high convergence 1 rod: 10 bipolar: 100 retinol ganglion
high sensitivity and low resolution

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17
Q

How can we have clear and detail vision if incoming light is distorted and there is a blind spot?

A

the fovea, perceptual completion, and eye movements

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18
Q

Fovea

A

allows high acuity vision due to the high density of receptors

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19
Q

Perceptual completion

A

the brain does “tricks” and fills in information in the blind spot based on context and past experience

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20
Q

Saccades

A

rapid eye movements; the perceived image is a sum of inputs received during the last few fixations (like quick camera snapshots)

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21
Q

Scotoma

A

an area of blindness caused by damage in the visual cortical area; damage in cortical areas affects signal processing due to retinotopic organization

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22
Q

Blindsight

A

the ability to see despite cortical-induced scotoma; happens due to alternative visual pathways (superior colliculus)

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23
Q

What happens if images are stabilized on the retina (the eye is not moving)?

A

The neurons stop firing and the image begins to fade (no input = image fades); the neurons respond to change

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24
Q

Differences between retinal images and photographs

A

photographs are exact copies while our visual system makes good “guesses”; what we see is our brain drawing on experiences and context

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25
Q

The lens of the eye projects on to the retina a _____, ______, and _____ image

A

focused, inverted, reversed

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26
Q

Photoreceptors transduce light into ____

A

neural firing patterns

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27
Q

How does the brain make sense of these sequences of impulses originating from different parts of the retina?

A

firing patterns are transmitted to the bipolar and horizontal cells, then transmitted to the endocrine and ganglion cells before bundling in optic nerve which is the sent to the brain (gets more ordered at each level of processing so you perceive the image focused and at the right orientation)

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28
Q

Retina-geniculate-striate pathway

A

major visual information processing pathway

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29
Q

Visual signal from each visual field goes to the ______ hemisphere

A

contralateral (e.g. objects in the left visual field => brain structures in the right hemisphere)

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30
Q

If there is a lesion in the right optic nerve, how is vision affected?

A

the right eye cannot see, the left eye is not impacted

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31
Q

If there is a lesion in the optic chiasm, how is vision affected?

A

damage with contralateral pathways (the LVF of left eye cannot see and the RVF of the right eye cannot see)

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32
Q

If there is a lesion in the right V1, how is vision affected?

A

the LVF of both eyes cannot see (left nasal and right temporal)

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33
Q

Visual Thalamus (LGN)

A

main subcortical nuclei that carries visual signals to the cortex
6 layers of cells
recieves 90% of retinal input

34
Q

Input from each eye is ______ in the LGN

A

separate; monocular

35
Q

Primary Visual Cortex

A

(also called V1 or striate)
6 layers of cells; LGN projects to layer 4
first stage of visual processing in cerebral cortex

36
Q

Visual organization

A

Retinotopic organization
disproportionate cortical representation of the fovea

37
Q

Higher concentration of receptors in a retinal area is associated with

A

larger cortical representation and higher acuity

38
Q

What is the visual receptive field?

A

the area of the retina that when stimulate with light, changes the cell’s activity
has two areas, a center and a surround, producing opposite repsonses (light in center might be excitatory with the surround inhibitory or the opposite)

39
Q

Two forms of visual receptive fields

A

circular (RGN, LGN)
rectangular (V1)

40
Q

What are the properties of the on-center cell?

A

the on-center excites the neural firing while the off-surround inhibits firing

41
Q

If light is shone in both the on-area and off-area at the same time the response is ____

A

weakend

42
Q

What is the correlation between receptive field size and discrimination?

A

smaller receptive field = finer discrimination

43
Q

How does the receptive field of neurons in the fovea compare to those in the periphery?

A

the RF of neurons in the fovea are smaller than in the periphery, allowing finer discrimination

44
Q

Retinal Ganglion cells most respond to

A

small spots of light

45
Q

Neurons in the V1 most respond to

A

bars of light

46
Q

None of the receptors respond to

A

background or diffuse light; neurons respond to change/contrast

47
Q

Two major classes of V1 neurons and properties

A

Simple cells:
- respond to lines/bars of specific orientation
- RF has a clear on/off area
Complex cells:
- larger RFs than those of simple cells
- binocular
- 3D vision begins here

48
Q

Receptive fields of neurons in the foveal area of LGN or V1 are ____ than those in the periphery area

A

smaller

49
Q

Contrast enhancement

A

mechanism in the visual system that enhances perception of brightness contrast between two areas

50
Q

Perception is a _____ property

A

cortical

51
Q

How does lateral inhibition work?

A

when a receptor fires, it also inhibits neighboring receptors

52
Q

The Hermann Grid Illusion demonstrates

A

there is some lateral inhibition at the retinal level

53
Q

If light alters the firing of a small group of receptors, what is the effect on the on-center bipolar cell that is directly connected to those receptors? What is the effect on the nearby cells? What causes this effect?

A

Excitatory; Inhibitory; Lateral Inhibition

54
Q

Component theory

A

perception of color can be explained by different receptors (cones) in the retina

54
Q

Opponent process theory

A

occurs at all levels of the visual system beyond receptors; opposing colors and complementary afterimage

55
Q

Retinex theory

A

refers to the observation of color constancy and color contrast - the perception of object color is determined by its reflectance in a context

56
Q

What behavioral phenomenon might have contributed to your percieved color?

A

color constancy and contrast

57
Q

Which of the following most likely gives rise to the behavioral phenomenon of color constancy?

A

neural processing at the cortical level

58
Q

Regions beyond the striate cortex are called

A

extrastriate areas

59
Q

Cells in the extrastriate areas have ____ visual receptive fields

A

larger

60
Q

Dorsal stream

A

where and action pathway; directing behavioral interactions with objects

61
Q

Ventral stream

A

responsible for concious recognition (perception) of objects

62
Q

Control of behavior vs. conscious perception

A

dorsal - directing behavioral interactions with objects
ventral - responsible for conscious recognition of objects

63
Q

Visual Agnosia

A

inability to recognize visual image

64
Q

Prospagnosia

A

inability to recognize faces

65
Q

What about the existence of different visual agnosias tell us about visual processing in the brain

A

there might be separate object recognition processes in the visual system

66
Q

Simple and complex cells are alike in that

A

they are unresponsive to diffuse light

67
Q

V1 neurons are most responsive to

A

sine-wave gratings of light in particular orientation

68
Q

A patient with a lesion to the ventral stream is able to interact with an object, and yet has no conscious perception of the object. This is explained BEST by which visual pathway theory?

A

The “control of behavior” vs. “conscious perception” pathway

69
Q

What is a valid interpretation of the “Halle Berry neuron”?

A

The properties of this type of neurons may reflect broader face processing patterns found within the recorded region which may relate to emotional salience, semantic processes, or facial recognition

70
Q

If you forced someone to guess what an object found within his scotoma is, he may be able to guess correctly due to:

A

alternative visual pathways

71
Q

Why can the eye, in particularly the retinal layers, be described as “inside-out”?

A

Light must pass through multiple cell layers before reaching the cells capable of responding to light.

72
Q

From the eye, visual information first travels mostly to which of the following in the mammalian brain:

A

the lateral geniculate nucleus

73
Q

Even though we blink and move our eyes, we do not see objects around us as disappearing or blurry momentarily. This is because of:

A

temporal summation across recent inputs

74
Q

Compared to the scotopic system, the photopic system

A

has less convergence.

75
Q

What does the “component theory” propose?

A

color perception emerges from the relative activity in three types of photoreceptors

76
Q

Even though we blink and move our eyes, we do not see objects around us as disappearing or blurry momentarily. This is because of:

A

temporal summation across recent inputs

77
Q

The visual areas are organized like _________, which refers to the fact that _________

A

a map of the retina; adjacent neurons have adjacent receptive fields

78
Q

Information from the left visual field of the right eye will travel to

A

the right LGN

79
Q

What best explains the disproportionate representation of the fovea in the primary visual cortex?

A

the high density of visual receptors in the fovea

80
Q

The fovea
Question options:

consists exclusively of rods.

creates the blind spot.

is the area of the retina that has the greatest sensitivity.

none of the above

A

none of the above

81
Q
A

Biopsychology (10 decks)

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