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Biopsych Midterm 3 > Ch.6 Pt.2 > Flashcards

Ch.6 Pt.2 Flashcards

(61 cards)

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1
Q

Perception of an edge

A

Perception of a contrast between 2 areas of the visual cortex
- Contrast enhancement happens at all edges in the visual field

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2
Q

What are Mach Bands?

A

Nonexistent stripes the visual system creates for contrast enhancement

  • Making edges easier to see
  • resulting in lateral inhibition
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3
Q

What is Ommatidia?

A

Photoreceptors that have individual axons that are connected in a network

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4
Q

What are the two properties of Ommatidia?

A
  1. firing intensity is directly proportional to the intensity of the light stimulus
  2. Firing of one ommatidia inhibits the firing of the adjacent ommatidia - lateral inhibition
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5
Q

How can contrast inhibition be understood?

A

Using lateral inhibition

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6
Q

Neural Mechanism for Contrast Enhancement Eg:

A
  • A,B,C,D all receive light of the same intensity
  • E,F,G,H all receive light of the same intensity
  • D fires more rapidly than A,B,C
  • E fires less rapidly than F,G,H
  • Ommatidia D receives the same amount of light as A B C, but less lateral inhibition from E. THEREFORE the response of this receptor is faster
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7
Q

Hubel and Wisel studied what 3 levels of the visual system?

A
  1. Reinal Ganglion Cells
  2. Lateral Geniculate Nucleus of Thalamus
  3. Neurons of lower layer IV (4) Cortex
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8
Q

What are the 4 Common Traits of cells between these 3 levels of the visual system?

A
  1. Fovea is always characterized by cells with smallest visual fields
  2. Receptive fields always circular
  3. Each neuron had a receptive field in one eye(monocular)
  4. Many neurons have a part of their visual field that is excitatory and others that is inhibitory
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9
Q

Hubel and Wiesel Receptors Fields

A

Many cells have recenter surround organization: excitatory and inhibitory regions separated by a circular boundary

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10
Q

Some cells are ___ and some cells are ____

A

On-center and Off-center

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11
Q

On Firing

A

Bursts of firing when light is turned on inside the receptive field

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12
Q

Off Firing

A

Bursts of firing when light is turned off inside the receptive field. Neuron is inhibited when light is on

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13
Q

On Center Off surround cell

A
  • Light on at centre of receptor field- firing
  • light on at periphery of receptor field - inhibited
  • Light off at periphery of receptor filed - fire
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14
Q

Off centre On surround cell

A
  • Light off at centre of receptive field - fires
  • Light on at centre of receptive fuel - inhibited
  • Light on at periphery of receptive field - fires
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15
Q

What do lower IV layer cells respond best to?

A

Contrast

- These cells are continuously active, when contrast is enhanced you either get and increase or decrease in firing rate

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16
Q

What happens to the firing rate if the visual field is diffusely illuminated (the spread of light)?

A

You get no change in the firing rate

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17
Q

How is information encoded?

A

In the frequency of Action potentials

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18
Q

What is rare to find in lower layer IV of the striate cortex?

A

Neurons with circular receptive fields (as in retinal ganglion cells and LGN)

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19
Q

Most neurons in V1 are either:

A
  • Simple - receptive fields are rectangular with “on” and “off” regions
    OR
  • Complex - also rectangu;ar, with large receptive fields, and respond best to a particular stimulus anywhere in their receptive fields
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20
Q

Receptive Fields of Simple Cortical Cells:

A
  • Have on and off regions of they receptive fields and are monocular (get info from one eye)
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21
Q

Simple cortical cells differ in 2 ways from lower layer IV neurons:

A
  1. The boarders of the on and off portions of their receptive fields are straight and not circular
  2. They respond maximally to bars of light at the correct orientation space
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22
Q

Receptive Fields of Complex Cortical Cells

A
  • Complex cells are more common than simple
  • Larger receptive fields than simple
  • on and off portions of the receptor field are NOT static (meaning: these cells repond to a bar of light in the correct orientation regardless of its position in space with the receptive field
  • Receptive fields can be binocular
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23
Q

3 Similarities between Simple and Complex Cortical cells

A
  1. They both have rectangular receptive fields
  2. Respond maximally to bars of light in correct orientation
  3. Unresponsive to spreading of light
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24
Q

What does “The receptive field may be Binocular” mean?

A

Receptor may respond to visual stimulation from either eye.

- May respond maximally when both eyes stimulated vs only one

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25
What is ocular dominance?
If response to stimulation in the visual field is stronger in one eye than another
26
What is Retinal Disparity?
The slight difference in the two retinal images due to the angle from which each eye views an object
27
Columnar Organization of Primary Visual Cortex
Cells with simpler receptive fields send information on to cells with more complex receptive fields
28
What is true about functional vertical columns?
All cells in a column have the same receptive field and ocular dominance
29
Ocular dominance columns:
As you move horizontally, the dominancee of the columns changes
30
It is commonly held that mechanisms of visual processing can be identified using..
Simplified artificial visual stimuli
31
Contextual influences in visual processing commonly holds that receptive fields of visual neurons are what?
A Static property of these cells
32
What appears to be a fundamental property of visual cortex function?
Plasticity ( Quality of being easily shaped or moulded) | -THEREFORE a neurons receptive field is plastic and is continuously fine tuned based on visual signals about context
33
What does colour vision depend on?
Wavelengths of light that reflect onto the eye
34
Objects absorb different wavelengths of light and reflect the rest, what does the reflected light of various wavelengths influence?
Our perception of colour
35
What are the observation and hypothesis of the Component Colour Theory (trichromatic)?
- Observation: A color on the visual spectrum can be made by mixing light of 3 different wavelengths in different proportions - Hypothesis: there must be 3 types of photoreceptors for colour vision 1. Short cones 2. Medium cones 3. long cones
36
Opponent Process Hypothesis:
- Two different classes of cells encoding colour - Third class of cell encoding brightness - Each encodes two complementary colour perceptions (red:green/ yellow:blue) - This theory accounts for colour after images and colours that cannot appear together (reddish green or bluish yellow) TEXT BOOK DEFINITION: The theory that a visual receptor or a neuron signals one colour when it responds in one way (e.g by increasing its firing rate) and signals the complementary colour when it responds in the opposite way )e.g. by decreasing the firing rate)
37
Component vs Opponent Theories:
Both theories are correct - Coding of colour by cones (retina) seems to operate on a purely component basis - Opponent processing of colour is seen at all subsequent levels (LGN, cortex
38
Color constancy:
- Color percerception is not altered by varying wavelengths
39
Retinex Theory:
Color is determined by a proportion of light off different wavelengths that a surface reflects
40
Releative wavelengths are constant so what does that mean for perception?
It is constant too
41
Dual- opponent color cells:
They are sensitive to colour contrast. Similar to on and off cells but instead respond to specific wavelengths (colour) or light
42
Where are Dual-opponent colour ells found?
- Incortical "blobs"
43
What is the order of the Flow of Visual Information:
1. Retina 2. Lateral Geniculate (Thalamus) 3. Primary Visual Cortex (Striate Cortex) 4. Seconday Visual Cortex 5. Visual Association Cortex
44
Primary Visual Cortex:
- Receives the most visual information from the thalamus | - Located at the posterior portion of the occipital cortex
45
Secondary Visual Cortex
- Receives most of the input from primary visual cortex | - Localized to the prestriate cortex to the inferotemporal cortex
46
Visual Association Cortex:
Cortex that receives input from secondary visual cortex as well as information from other sensory modalities - Localized to the posterior parietal cortex
47
Damage to the Primary Visual Cortex results in
1. Scotomas 2. Completion 3. Blindsigh
48
What is scotomas?
Areas of blindness in both eyes due to damage of the PVC
49
What is completion?
The visuals system automatic use of information from receptors around the blindspot, or scotoma to create a perception of the missing portion of the image
50
Blindsight
The ability of some patients who are blind due to cortical damage to unconsciously see some aspects of their visual environment
51
Neurons in each area of secondary and association visual cortex respond to different visual cues, such as
colour, movement, or shape. | - Lesions of each area result in specific deficits
52
Anatomically distinct:
about 12 functionally distinct areas identified so far
53
Dorsal Stream
Pathway from primary visual cortex to dorsal pre striate cortex to posterior parietal cortex - The 'WHERE" pathway (location and movement ) - Or pathway for the control of behaviour (e.g Reaching)
54
Ventral Stream:
Pathway from primary visual cortex to ventral pre striate cortex to inferotemporal cortex - the "WHAT pathway (colour and shape) or Pathway for the conscious perception of objects
55
What is Prsopagnosia?
- Inability to distinguish among faces | - Although most deficits are not limited to faces
56
What is Prosopagnosia associated with?
damage to the ventral stream (between the occipital and temporal lobes)
57
True or False: Prosopagnosics may be able to recognize faces in the absence of conscious awareness awareness
true
58
Prosopagnosics have different skin conductance in response to what?
Familiar compared to unfamiliar faces, even though they reported not recognizing any of these faces
59
Akinetopsia
Deficiency in the ability to see movement progress in a normal, smooth fashion
60
Akinetopsia can be induces by what?
A high dose of antidepressants
61
What damage is Akinetopsia associated with
The middle temporal (MT) of the cortex

Biopsych Midterm 3 (4 decks)

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