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Intro to Brain and Behaviour > Visual System > Flashcards

Visual System Flashcards

1
Q

What is light?

A

Waves of electromagnetic energy

Wavelengths that are visible to humans

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2
Q

What are the two properties of light?

A

Wavelength (colour)

Intensity (brightness)

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3
Q

How does light work with your eye?

A

Light enters the eye through the pupil and reaches the retina

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4
Q

How is the amount of light that reaches the retina regulated?

A

Pupil size
- regulated by iris - regulates the size of the pupil to regulate the amount of light that comes in (which gives your eye its colour)

Pupil size is compromise between sensitivity (ability to see objects) and acuity (ability to see details)

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5
Q

What is involved within the lens of the pupil?

A

Focuses incoming light on the retina

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6
Q

What is focus called within the lens

A

Accommodation

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7
Q

What does it mean when the lens is cylindrical?

A

When focused on something near

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8
Q

What does it mean when the lens is flattened?

A

When focused on something far away

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9
Q

Why is eye position important?

A

Most mammals have two eyes on the front of their heads - compared to some animals with eyes on the side of their heads

Most of what is seen is seen through both eyes

Eyes see things from a slightly different perspective

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10
Q

What is binocular disparity?

A

The difference in the two retinal images
-Greater for closer things
- Helps create depth perception (3D perception) - takes two-dimension perspectives to turn it into one 3 dimensions perspective

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11
Q

Whats the difference between predators and prey eye placement

A

Predators - eyes in front; helps predictors build dept-preception to hunt prey (Owls)

Prey - eyes on side; Better view to escape a predator by running away (Mice)

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12
Q

What are the five layers of the retina (the structure of the back of the eye) in order

A

-Retinal ganglion cell layer (near the front of the retina)
-Amacrine cell layer
-Bipolar layer
-Horizontal cell layer
-Receptor layer (farthest from the light) - the back of the retina

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13
Q

What are two important components of the fovea?

A

Location

High-acuity vision - think of the times trying to thread a needle

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14
Q

What two important components of the optic disk or optic nerve?

A

Blind spot

Completion (filling in)
- The axons on the retinal ganglion cells must leave a gap, in the receptor layer, which creates a blind spot

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15
Q

What is duplexity theory?

A

Rods and cones mediate different types of vision

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16
Q

What are the red coloured and blue coloured cells respectfully?

A

Red coloured cells are cones

Blue coloured cells are rods

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17
Q

What is photopic? - one of two visual systems

A

Cone-mediated, lighted conditions

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18
Q

What is scotopic? - one of the two systems

A

Rod-mediated, dim light

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19
Q

What is the difference between low and high degree convergence?

A

Low degree of convergence in cone-fed pathways (one receptor)

High degree of convergence in rod-fed pathways (multiple receptors)

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20
Q

What is spectral sensitivity?

A

More intense lights appear brighter

Wavelength can impact the perception of brightness

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21
Q

What does differential sensitivity to wavelengths mean?

A

Lights the same intensity, but of different wavelengths, can differ in brightness

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22
Q

What is spectral sensitivity curves?

A

Relative brightness of lights at different wavelengths

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23
Q

What does it mean when fixtion occurs during eye movement?

A

Continous movement usualy occurs, if stopped, then the visual image will disappear around the one fixations

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24
Q

What is saccades during eye movement?

A

Rapid movements between fixations - fixations are connected by these rapid movement

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25
What is a temporal integration in eye movement?
Sum of the inputs Explains why images are detailed , coloured, and wide-angled Explains why things don't disappear when we blink Eyes are always moving, keeping up to date on the visual environments and adds this information together
26
Why do images start to disappear due to eye movement?
Most visual neurons respond to change so if you block the change (artificially stabilized) then images start to disappear
27
What is visual transduction?
Transduction is the conversion of energy Visual transduction is conversion of light to neural signals by the visual receptors
28
How does transduction occur by rods?
1. Rhodopsin is bleached 2. Separates into retinal and opsin 3. Hyperpolarizes the rods 4. At rest, rods are slightly depolarized 5. Rods transmit signals through inhibition
29
How does the inhibitory response to rods to light work?
When light bleaches rhodopsin molecules, the rods' sodium channels close; as a result, the rods become hyperpolarized and release less glutamate Rods transmit signals through the neural system via inhibition
30
Where does the retina's information travel from?
From rods and cones
31
Where does the geniculate's information travel from?
Located from the thalamus
32
What are the two different pathway from the retina-geniculate-striate system that visual information can take
Nasal hemiretinas decussate (crosses) at optic chiasm Temporal hemiretinas stay ipsilateral (remains on the same side of the body)
33
What is the parvocellular layer in the M and P channels
Top four layers of lateral geniculate nucleus Composed of small-body (parvo) neurons Responsive to colour, fine detail, slow/stationary objects
34
What is the magnocellular layers in the M and P channels
Bottom two layers of lateral geniculate nucleus Composed of large (mango) body neurons Responsive to rods and movements
35
What is the Hubel and Wiesal methodology in order? (4 components)
1. Visual stimuli presented on a screen 2. Subject is curarized - blocked eye movements by freezing it 3. Extracellular electrode placed in one neuron 4. Neuron's receptive field is mapped
36
What is the receptive field of visual neurons?
The area of the visual field where appropriate visual stimuli can influence neuron firing
37
What are the receptive fields of a sensory cell?
The stimulus region and the features that excite or inhibit the cell
38
What are 3 very similar receptive fields in the retina-geniculate-striate system
1. Retinal ganglion cells 2. Lateral geniculate nucleus neurons 3. Lower layer IV of striate cortex
39
What are the similar characteristics of the receptive fields
-Smaller in the foveal area - Circular - Monocular -Excitatory and inhibitory area separated by a circular boundary
40
What are the two patterns of responding with respect to firing?
On firing: burst of firing when light was turned on Off-firing: inhibition of firing when the light was turned on, burst of firing when light was turned off
41
Whats the difference of on-center and off-center cell responses
On-center firing: When a spot of light is shone anywhere in the center of the field There is an "off" response when a spot of light is shone anywhere in the periphery of the field Off-center firing: When a spot of light is shone anywhere in the center of the field There is an "on" response when a spot of light is shone anywhere in the periphery of the field
42
What are some characteristics of firing?
Responds to brightness contrast between centers and peripheries of their visual fields Responds. best to fully illuminated "on" or "off" area Responds poorly to diffuse light
43
What are some simple striate cells?
Responds best to bars or edges in a particular location and orientation Monocular
44
What are some complex straite cells?
Responds best to straight lines of particular orientation Many complex cells are binocular
45
Retinal ganglion cells with receptive fields are selective too?
1. Uniform illumination 2. Orientation 3. Motion 4. Direction of motion
46
Lateral geniculate cells have receptive fields are sensitive to
1. Orientation 2. Motion 3. Direction of motion
47
How do contextual influences shape properties of the receptive fields?
Timing, location, amount of light but also particular actions or emotional states
48
What is the primary visual cortex responsible for
Located in occipital lobe Recieves most inputs from visual relay nuclei of thalamus
49
What is the secondary visual cortex responsible for?
Located in the prestriate cortex (surrounds primary visual cortex) Recieves input from primary visual cortex
50
What is the visual association cortex responsible for?
Areas - Inferotemporal cortex -Posterior parietal cortex Recieves input from secondary visual cortex
51
What results from damage to the primary visual cortex
Areas of blindness in corresponding areas of visual field Scotomas are plotted by perimetry tests
52
What is completion?
Your visual system "completes" an image when your unable to see - it fills in the blank of an image Many patients with large scotomas are unaware of them bc of this
53
What is blindsight?
The ability to respond to visual stimuli in a scotoma with no conscious awareness Thought to be mediated by visual pathways that are not part of the retina-geniculate-straite system
54
What are the portions of secondary and association cortex do
Areas specilized for particular type of visual analysis Connections between areas have been identified using anterograde/retrograde tracing
55
What responsibilities does the dorsal stream have?
Information flows from primary visual cortex Travels through dorsal prestriate secondary visual cortex Ends in associations cortex of posterior parietal region Originally proposed to be "where" pathway More recently proposed to be behavioural control path
56
What reponsibilities does the ventral stream have?
Information flows from primary visual cortex Travels through the ventral prestraite secondary visual cortex Ends in association cortex of posterior parietal region Originally proposed to be "what" pathway More recently proposed to be conscious perception pathway
57
What is agnosia?
Failure to recognize
58
What is prosopagnosia?
Inability to recognize faces May not be specific to faces - Difficulty distinguishing between visually similar members of stimuli Associated with damage to fusiform face area - area between the occipital and temporal lobes - Confirmed prosopagnosia suffers could recognize faces unconsciously (with a change in skin conductance)
59
What is akintospia?
Deficiency in the ability to see smooth movement Can be triggered by high doses of antidepressants Results of damage to the medial temporal area (MT)
60
What are the four lines of research that support MT as the area being affected by akintospia?
Patients with damage tend to have unilateral or bilateral damage to MT Activity in the MT increases when humans view movements (fMRI) Blocking activity of the MT with TMS produces motion blindness Electrical stimulation of the MT induces visual perception of motion

Intro to Brain and Behaviour (4 decks)

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