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PSGY1003 Biological Psychology > primary and visual pathway > Flashcards

primary and visual pathway Flashcards

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1
Q

How does visual information come into the brain?

A
  • main pathway
  • photoreceptors from retina in back of eye
  • information carried from retina to lateral geniculate nucleus via optic nerve
  • this is the visual relay station for sensory thalamus
  • information sent to occipital cortex, primary visual cortex of occipital lobe
  • located in occipital lobe (back of brain)
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2
Q

what makes up total field of view?

A
  • left visual field
  • right visual field
  • central field of view (where visual fields overlap)
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3
Q

when visual fields of both eyes overlap, which portion of the eye is hit?

A

Fovea

  • central vision is what we use to see something in focus, something sharp, near vision for reading
  • all of this involved the fovea
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4
Q

what is the lateral geniculate nucleus?

A
  • relay station of sensory thalamus
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5
Q

how is sensory information relayed?

A
  • via a specific nucleus of the thalamus
  • to primary sensory cortex found in most modalities
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6
Q

where does information from right visual field end up in the brain?

A

the left side

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7
Q

where does information from left visual field end up in the brain?

A

the right side

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8
Q

identify a key principle of information processing

A

information processing is hierarchical

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9
Q

outline the stages of information-processing stages in primary visual pathway

A

RETINA
- photoreceptors
- bipolar cells
- retinal ganglion cells

-optic nerve-

LATERAL GENICULATE BODY

VISUAL CORTEX

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10
Q

describe an experimental set up to record visual responses of neurones along the visual pathway

A
  • present visual information
  • visual information can be controlled
  • present visual information in field of view
  • using micro electrodes, electrophysiological recordings of neural activity at these different stages
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11
Q

identify other ways of recording visual responses of neurones along the visual pathway

A
  • fMRI
  • EEG
  • MEG
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12
Q

identify the two main types of photoreceptors contributing to vision

A
  • rods
  • cones
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13
Q

describe Rods

A
  • cannot discriminate wave lengths (therefore cannot discriminate colour)
  • 120 million in human retina (more abundant than cones)
  • sensitive in low light
  • higher density in periphery
  • tracks high-rate changes
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14
Q

describe Cones

A
  • 6 million in human retina
  • can discriminate 3 types of wavelengths (small, medium, large)
  • less sensitive in low light
  • higher concentration in fovea
  • cannot track high-rate changes
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15
Q

what are the photoreceptors detection of light translated into?

A
  • excitation or inhibition of retinal ganglion cells
  • via bipolar cells
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16
Q

what do bipolar cells do?

A

links photoreceptors to retina ganglion cells

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17
Q

what do photoreceptors and bipolar cells vary as they are stimulated?

A

voltage

(analogue signal)

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18
Q

what is the receptive field?

A
  • refers to portion of retina/visual field
  • this is where visual stimulation will evoke a change in firing rate
  • the size of the receptive fields gets bigger as more information is combined from several photoreceptors
  • very small receptive field at photoreceptor stage
19
Q

what does a ‘substructure of a receptive field’ refer to?

A
  • refers to the specific way visual stimuli/information is presented in the receptive field of a visual neurone
  • this is so a firing-rate change can be evoked
20
Q

outline the steps that take place from when retinal ganglion neurones receive visual input

A
  • neurones receive input from multiple photoreceptors
  • receive input via bipolar cells
  • bipolar cell receptive fields become several times the size of photoreceptor field as more information comes in
  • bipolar cell receptive fields have ‘on’ and ‘off’ and ‘centre’ surround structure
21
Q

what are bipolar cells?

A
  • one of the main retinal interneurons and provide the main pathways from photoreceptors to ganglion cells,
  • i.e. the shortest and most direct pathways between the input and output of visual signals in the retina
22
Q

what structures does bipolar cell receptive fields have?

A
  • on structure
  • off structure
  • centre surround structure
23
Q

what happens when light is presented in ‘on’ regions of bipolar cell receptive field?

A
  • cells become excited
  • increase in firing
24
Q

what happens when light is presented in ‘off’ regions of bipolar cell receptive field?

A
  • cells become inhibited
  • firing rate decreases
25
Q

explain the rebound effect

A
  • when stimulus is taken back, firing rate shoots in the opposite direction to what light stimulus was
  • following inhibition, neurone doesn’t go straight to baseline rate
26
Q

what happens when the light information is in the centre?

A
  • firing rate increases
  • when light information taken away, rebound effect occurs
27
Q

what is the response rate of the bipolar cells based on?

A

sum in ON stimulation - sum of stimulation in OFF region

28
Q

when will neurones only react?

A
  • when there is contrast and boundaries
29
Q

why is it important for there to be contrast and boundaries?

A
  • more efficient
    world has many things that stay constant
    therefore we don’t need to respond to it all the time
    more efficient to respond to changes and boundaries
  • helps preserve appearance of objects regardless of environmental light levels
    luminance of features = represented relative to their surround
    can result in illusions
30
Q

how is colour sensitivity perceived by retinal ganglion and lateral geniculate neurones?

A
  • both receive input from cones
  • you have different types of colour sensitive retinal ganglion and LGN
  • both have receptive fields
  • receptive fields have centre-surround organisation
  • centre = stimulation of certain light property causes excitation
  • surround = stimulation of certain wavelengths causes inhibition
31
Q

what different types of colour-sensitive retinal ganglion and LGN are there?
(colour opponency)

A
  • yellow on, blue off
  • yellow off, blue on
  • red on, green off
  • red off, green on
32
Q

what can colour opponency explain?

A

visual illusion

33
Q

from the lateral geniculate body in the thalamus, where is information then passed on to?

A

first visual processing stage

primary visual cortex

34
Q

where does the primary visual cortex (in humans) sit around?

A

Carlcarine fissure (between the hemispheres)

35
Q

identify a key feature of the neurones in the primary visual cortex

A

they are all orientation selected

36
Q

what is meant by ‘orientation-selective’ neurones?

A
  • neurones have bigger receptive fields than the neurones at stages before
  • they respond to light/elongated stimulation presented in a certain orientation
  • stimuli = elongated
37
Q

what are the type main types of orientation-sensitive primary visual cortex neurones?

A
  • simple cells
  • complex cells
38
Q

explain what simple cells are

A
  • they have receptive fields with inhibitory and excitatory regions
  • only become excited if stimulus is presented in the right orientation on this excitatory region
  • combines inputs from ON and OFF cells in LGN
  • integrates information from several LGN
39
Q

explain what complex cells are

A
  • a step up in regards to processing compared to simple cells
  • they combine information/inputs from several simple cells
  • their fields have no discrete on and off regions
  • but they respond best to moving stimuli (which reflects response adaptation - the neurone stops firing/reduces firing rate if stimulus doesn’t move)
40
Q

what is the Retino-topic map?

A
  • refers to the orderly mapping of retina/visual field onto visual cortex
  • different points of the retina interact with specific points in the primary visual cortex
  • neighbouring areas in the retina excite/interact with neighbouring areas in primary visual cortex
41
Q

what are modules of the primary visual cortex?

A
  • PVC divided into small columnar modules that combine neurones
  • these are sensitive to different aspects of stimuli presented in small part of visual field
  • some respond to stimuli of different orientation
  • some respond to colour
42
Q

what is ‘Blindsight’?

A
  • the ability to respond to visual stimuli without consciously perceiving them
  • a condition which can occur after certain types of brain damage
    (lesions to primary visual cortex)
43
Q

give examples of blindsight?

A
  • looking (moving eyes) or pointing to visual stimuli
  • but not being able to ‘see’ stimuli
44
Q

what does ‘blindsight’ highlight?

A
  • primary visual pathway = critical for conscious vision
  • there are also additional visual pathways
  • brain can perform visual information processing which can guide subjects’ behaviour without their conscious awareness

PSGY1003 Biological Psychology (21 decks)

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