~Chapter 3 - Lectures Flashcards

1
Q

Horseshoe Crabs eye are positioned ___ on their head

A

Laterally

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2
Q

What is a Compound eye?

A

An eye where each facet of the compound eye, which is called an Ommatidium, functions as a separate, or independent photoreception unit

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3
Q

Who used Horseshoe Crabs to research eyes?

A

Hartline

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4
Q

Omaatidium are connected by ___

A

Axons referred to as the Lateral Plexus

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5
Q

What happens during Lateral Inhibition?

A

Stimuli lateral to the recorded neuron appear to inhibit the neuron’s response

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6
Q

What Illusions are often used in examples of Lateral Inhibtion?

A

Chevreul (staircase) Illusion and Mach Bands

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7
Q

In the Mach Bands illusion, both the light and dark bands are ___

A

Illusory, when measuring the shadows with a light measure, you will see that both the light and dark bands are illusory, your visual system is telling you something is there when it is not

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8
Q

What is Center-Surround Antagonism?

A

Center-surround antagonism refers to antagonistic interactions between center and surround regions of the receptive fields of photoreceptor cells in the retina

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9
Q

What can Lateral Inhibition not explain?

A

Lateral inhibition at the level of the photoreceptors cannot explain the perceptions of the Chevreul illusion and Hermann Grid

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10
Q

There is a cycle between ___ that are created and the ___ that they predict

A

Physiological models // perceptions

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11
Q

Lateral Inhibition predicts the ___ than what is perceived in ___

A

opposite effect // White’s illusion

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12
Q

What happens when you change the connectivity of neural circuits?

A

You change their properties and function

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13
Q

What is the visual system definition of a Receptive Field?

A

An area on the retina that when stimulated with some pattern of light can affect the firing of a neuron.
But also because of the optics of the eye, it can be thought of as an area out in your visual field in your space, that when stimulated, can affect the firing of a neuron.

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14
Q

What is the function of Receptive Fields?

A

Receptive fields analyze the images of objects in the world

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15
Q

What are Center-Surround Receptive Fields that have Center-Surround Antagonism?

A

Donut-shaped area that prefers one type of stimulus and the central area prefers another type of stimulus.

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16
Q

___ regions are excited by luminance increment

A

“On”

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17
Q

___ regions are excited by decrement

A

“Off”

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18
Q

What cells have Center-Surround Receptive Fields?

A

Retinal Ganglion cells, Bipolar cells, and photoreceptors

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19
Q

What happens when you shine a light on an “Off” region in a Center-Surround Receptive Fields?

A

The cell is going to be inhibited, and it’s going to not fire any spikes.

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20
Q

What happens when you shine a light on an “On” region in a Center-Surround Receptive Field?

A

There is a strong response in firing

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21
Q

You are shining a light onto an “On” region in a Center-Surround Receptive Field, you then turn the light off, what happens?

A

The cell stops responding/firing

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22
Q

You are shining a light into an “Off” region in a Center-Surround Receptive Field, you then turn the light off, what happens?

A

You’re going from brighter to darker and this counts as luminance decrement, that causes a burst in excitation of the cell

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23
Q

In Center-Surround Antagonism, the light and dark regions ___ each other

A

Oppose

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24
Q

You shine a light over both regions in a Center-Surround Receptive Field, what happens?

A

You get spontaneous activity where the cell is not excited or inhibited, it’s spontaneously firing.

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25
Q

Luminance Increment produces ___ in “On” regions and ___ in “Off” regions

A

Excitation // Inhibition

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26
Q

Luminance Decrement produces ___ in “On” regions and ___ in “Off” regions

A

Inhibition // Excitation

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27
Q

How does hyperpolarization in one cell create excitation in another?

A

Release from inhibition

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28
Q

If the neurotransmitter is being treated as inhibitory it will create a ___ which will create an ___ bipolar cell

A

Sign Inverting Synapse // on-center

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29
Q

Photoreceptors always release ___

A

Glutamate

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30
Q

Bipolar cells treat Glutamate as inhibitory to make an ___ response

A

on-center

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31
Q

Bipolar cells treat Glutamate as excitatory to make an ___ response

A

off-center

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32
Q

When you shine a light on a photoreceptor, ___ bipolar cells will become excited

A

on-center

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33
Q

If a neurotransmitter is being treated as excitatory it will create a ___ which will create an ___ bipolar cell

A

Sign Conserving Synapse // off-center

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34
Q

Photoreceptors release ___ glutamate when they are depolarized

A

More

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35
Q

Photoreceptors release ___ glutamate when they are hyperpolarized

A

Less

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36
Q

Photoreceptors are most simple at the ___

A

Synapse

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37
Q

On-Center Bipolar cells treat glutamate as ___

A

inhibitory

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38
Q

Off-Center Bipolar cells treat glutamate as ___

A

excitatory

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39
Q

How does Lateral Inhibition create Center-Surround Receptive Fields in the Retina?

A

By using Horizontal cells

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40
Q

Where does Lateral Inhibition occur?

A

On the Photoreceptors

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41
Q

What is the order of cells in the Visual Pathway?

A

Photoreceptors → Bipolar cells → Ganglion cells in the eye

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42
Q

The connections between Photoreceptors, Bipolar cells, and Ganglion cells are creating the ___

A

Center-Surround Receptive Field

43
Q

Who wanted to deconstruct how visual information was being worked on, step by step to gain insights about how visual information is processed (worked on) by the brain?

A

Hubel and Wiesel

44
Q

What is the Lateral Geniculate Nucleus (LGN)?

A

A multilayered structure that receives input from both eyes to build a representation of the contralateral visual hemifield.

45
Q

Where does the Lateral Geniculate Nucleus (LGN) receive input from?

A

Ganglion cells

46
Q

The LGN has neurons that have ___, just like the Retinal Ganglion cells

A

Centre-Surround Receptive Fields

47
Q

What is the function of the LGN?

A

The LGN controls information flow to the cortex, organizes visual information, and acts as a throttle/regulator to allow bottom-up information into the visual processing.

48
Q

l

A

.

49
Q

How does the LGN control info flow to the Cortex from the Cortex

A

Through Top-Down information

50
Q

What is controlling how much info can flow from the LGN to the Cortex?

A

Top-Down information from the Cortex

51
Q

Where do we see a transformation in the structure of receptive fields?

A

The Primary Visual Cortex

52
Q

What is the LGN and Top-Down info analogous to?

A

A bouncer at a club regulating who’s allowed to come in, being given orders by the club owner.

53
Q

Who discovered that there are several types of neurons in the primary visual cortex that have shape preference??

A

Hubel and Wiesel

54
Q

What do Simple Cells respond to?

A

Simple cells-respond to “bars” of light of a particular orientation (orientation selective)

55
Q

Do simple cells have “On” and “Off” regions?

A

Yes, but they’re elongated out into ovals

56
Q

What do neurons in the Primary Visual Cortex NOT contain?

A

Center-Surround Fields

57
Q

If you shine a light onto the “On” region of a Simple Cell, what will happen?

A

You’re going to get a strong visual response

58
Q

In a Simple Cell, if you shine a bar of light in a tilted orientation such that now, some of it is in the “On” region, but the ends are poking into the “Off” subregions, what will happen?

A

The On region is being antagonized/cancelled out by the “Off” subregions, so the firing rate is a little lower.

59
Q

In a Simple Cell, if you have the slit of light oriented horizontally, such that the same amount of light is on the On and Off subregions, what will happen?

A

They cancel out and you get spontaneous firing

60
Q

What is an Orientation Tuning Curve?

A

The orientation preference of a neuron

61
Q

How can you find out the Orientation Tuning Curve?

A

By counting the spikes per second when presenting stimuli at different orientations (x-axis orientation in degrees, y-axis spikes/second)

62
Q

Do Simple Cells respond to moving or stationary stimuli?

A

Both

63
Q

Are Simple Cells “On” and “Off” regions separate?

A

Yes, their “On” and “Off” regions are seperate

64
Q

In Simple Cells, when the stimuli are moving, they sometimes are direction selective, as long as they are ___

A

Orientated the correct way

65
Q

What do Complex Cells respond to?

A

Respond to “bars” of light of a particular orientation

66
Q

Are Complex Cells direction-selective?

A

Sometimes

67
Q

Can Complex Cells respond to moving or stationary stimuli

A

both

68
Q

Do Complex Cells have “On” and “Off” regions?

A

No, they do NOT have “On” and “Off” regions

69
Q

What does it mean if a Cell is Direction-Selective?

A

Meaning that not only does the stimulus have to be of the correct orientation, but the bar when it moves, it has to be going in a particular direction.

70
Q

How do you find the Direction Tuning Curve?

A

By counting the amount of spikes that are occurring when you’re presenting a stimulus. (x-axis spikes/second, y-axis direction)

71
Q

What do End-Stopped Cells respond to?

A

Respond to moving “bars” of light of a particular orientation and a particular length, or moving “corners”.

72
Q

What was the original name for End-Stopped Cells?

A

Hyper-complex cells

73
Q

What is Extra-Classical Modulation?

A

If you have a bar that is too long, you get a lack of response, but it’s not actually inhibition, because when you shine a light on the sides, the cells really don’t care about it, so they’re not inhibited by it.

74
Q

What was Hubel & Weisels underlying hypothesis?

A

Through each stage of processing, each cell will become more selective for these complicated features, and eventually what you might get is something as complicated as a human face or car, and this is how visual perception is built.

75
Q

What is a Selective Adaptation?

A

When a neuron sees a stimulus that it likes, it’s going to fire a lot, and when a neuron fires a lot, it gets tired, and it cannot fire as robustly when it’s tired as opposed to when it’s rested.

76
Q

Neurons with Feature Detector properties respond to ___

A

A specific type of stimulus

77
Q

What kinds of stimuli are used in Selective Adaptation studies?

A

Gratings which measure human participants contrast detection thresholds.

78
Q

What would be the contrast detection threshold in a study using grating?

A

When the difference between the light bits and the dark bits becomes so small that the field is very difficult to distinguish from just a homogenous grey field

79
Q

When happens when you adapt to vertical gratings?

A

You become less sensitive to vertical gratings and so it requires a large increase in the contrast, so it changes the contrast threshold by a large amount.

80
Q

What kind of study is explained by “use it or lose it”?

A

Developmental Studies

81
Q

In the primary visual cortex, neurons that are stimulated during development ___, and neurons that are not simulated ___

A

survive // are pruned away.

82
Q

What happened in the study where developing cats were shown only vertical grating?

A

When later tested behaviourally, they are only able to see vertical grating, and horizontal gratings appear to be virtually invisible.

83
Q

What appeared in the brain recordings of developing cats who were shown only vertical grating?

A

Their primary visual cortex is filled with neurons that respond to vertical gratings, but very few or none that respond to horizontal gratings.

84
Q

Orientation tuning is ___ during development

A

Plastic

85
Q

Who did experiments in the Inferotemporal Cortex (IT)?

A

Charles Gross

86
Q

Is the primary visual cortex or the Inferotemporal Cortex (IT) more advanced?

A

Inferotemporal Cortex (IT)

87
Q

What does the Inferotemporal cortex (IT) do?

A

The Inferotemporal cortex (IT) is important for processing objects, these cells become extremely picky and selective for very complex stimuli. Complex form Processing

88
Q

What kinds of responses are seen in the Inferotemporal Cortex (IT)?

A

“Elaborate” Cells in IT respond to complex visual stimuli

89
Q

In Charles Gross’ study on Monkey neurons in the IT, what had the highest response in firing rate?

A

Monkeys’ faces viewed from head-on.

90
Q

In Charles Gross’ study on Monkey neurons in the IT, what happened when features of the monkey’s face were removed?

A

The responses get weaker.

91
Q

In Charles Gross’ study on Monkey neurons in the IT, what happened when the monkey began to turn away?

A

The responses get weaker.

92
Q

What is Specificity Coding (Grandmother cell hypothesis)?

A

Like a pyramid structure, as you’re going up higher on the pyramid, the cells become more complex, you eventually get to the one cell that combines all these features together to make, for example, the cell that only responds to your grandmother and no other face

93
Q

What are Sensory Codes?

A

How neurons encode the visual world such that it can then produce this conscious experience

94
Q

Which Sensory Code theory is least likely?

A

Specificity Coding (Grandmother cell hypothesis)

95
Q

What is one problem with the Specificity Coding hypothesis?

A

Ambiguity.

96
Q

What is Distributed/Population Coding?

A

Where you’re measuring the pattern of activity across neurons, involves listening to multiple cells.

97
Q

What problem does Distributed/Population Coding help eliminate?

A

Eliminates the ambiguity that is created by only listening to one neuron

98
Q

Why doesn’t Specificity Coding work?

A

Specificity Coding suggests you have one specialized cell for recognizing every individual face and object, but we don’t have that many brain cells in our visual cortex to code for that

99
Q

How do we code so much about objects with so few neurons?

A

Distributed or Sparse Coding

100
Q

What is the difference between Distributed/Population Coding and Sparse Coding?

A

In Distributed/Population Coding, the population, all the neurons are more or less participating, and there are different patterns of population activity for different stimuli.

In Sparse coding it codes for slightly fewer, but you still have this unique pattern for each stimulus, it’s just that there are more members of the population that are silent.

101
Q

What is the difference between Distributed/Population Coding and Sparse Coding?

A

In Distributed cCoding, all the cells are activated in a different pattern. In sparse coding, some of the cells are more choosy and are sitting out until they see their favourite stimulus.

102
Q

Which Cortexes in the brain are more often associated with memory rather than visual processing, but the neurons have visual responses?

A

Parahippocampal and Entorhinal cortex

103
Q

Does LGN contain Centre-Surround RF’s?

A

Yes