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Intro to Brain and Behaviour > Visual System > Flashcards

Visual System Flashcards

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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
Q

What is a temporal integration in eye movement?

A

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
Q

Why do images start to disappear due to eye movement?

A

Most visual neurons respond to change so if you block the change (artificially stabilized) then images start to disappear

27
Q

What is visual transduction?

A

Transduction is the conversion of energy

Visual transduction is conversion of light to neural signals by the visual receptors

28
Q

How does transduction occur by rods?

A
  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
Q

How does the inhibitory response to rods to light work?

A

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
Q

Where does the retina’s information travel from?

A

From rods and cones

31
Q

Where does the geniculate’s information travel from?

A

Located from the thalamus

32
Q

What are the two different pathway from the retina-geniculate-striate system that visual information can take

A

Nasal hemiretinas decussate (crosses) at optic chiasm

Temporal hemiretinas stay ipsilateral (remains on the same side of the body)

33
Q

What is the parvocellular layer in the M and P channels

A

Top four layers of lateral geniculate nucleus

Composed of small-body (parvo) neurons

Responsive to colour, fine detail, slow/stationary objects

34
Q

What is the magnocellular layers in the M and P channels

A

Bottom two layers of lateral geniculate nucleus

Composed of large (mango) body neurons

Responsive to rods and movements

35
Q

What is the Hubel and Wiesal methodology in order?
(4 components)

A
  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
Q

What is the receptive field of visual neurons?

A

The area of the visual field where appropriate visual stimuli can influence neuron firing

37
Q

What are the receptive fields of a sensory cell?

A

The stimulus region and the features that excite or inhibit the cell

38
Q

What are 3 very similar receptive fields in the retina-geniculate-striate system

A
  1. Retinal ganglion cells
  2. Lateral geniculate nucleus neurons
  3. Lower layer IV of striate cortex
39
Q

What are the similar characteristics of the receptive fields

A

-Smaller in the foveal area
- Circular
- Monocular
-Excitatory and inhibitory area separated by a circular boundary

40
Q

What are the two patterns of responding with respect to firing?

A

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
Q

Whats the difference of on-center and off-center cell responses

A

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
Q

What are some characteristics of firing?

A

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
Q

What are some simple striate cells?

A

Responds best to bars or edges in a particular location and orientation

Monocular

44
Q

What are some complex straite cells?

A

Responds best to straight lines of particular orientation

Many complex cells are binocular

45
Q

Retinal ganglion cells with receptive fields are selective too?

A
  1. Uniform illumination
  2. Orientation
  3. Motion
  4. Direction of motion
46
Q

Lateral geniculate cells have receptive fields are sensitive to

A
  1. Orientation
  2. Motion
  3. Direction of motion
47
Q

How do contextual influences shape properties of the receptive fields?

A

Timing, location, amount of light but also particular actions or emotional states

48
Q

What is the primary visual cortex responsible for

A

Located in occipital lobe

Recieves most inputs from visual relay nuclei of thalamus

49
Q

What is the secondary visual cortex responsible for?

A

Located in the prestriate cortex (surrounds primary visual cortex)

Recieves input from primary visual cortex

50
Q

What is the visual association cortex responsible for?

A

Areas
- Inferotemporal cortex
-Posterior parietal cortex

Recieves input from secondary visual cortex

51
Q

What results from damage to the primary visual cortex

A

Areas of blindness in corresponding areas of visual field

Scotomas are plotted by perimetry tests

52
Q

What is completion?

A

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
Q

What is blindsight?

A

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
Q

What are the portions of secondary and association cortex do

A

Areas specilized for particular type of visual analysis

Connections between areas have been identified using anterograde/retrograde tracing

55
Q

What responsibilities does the dorsal stream have?

A

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
Q

What reponsibilities does the ventral stream have?

A

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
Q

What is agnosia?

A

Failure to recognize

58
Q

What is prosopagnosia?

A

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
Q

What is akintospia?

A

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
Q

What are the four lines of research that support MT as the area being affected by akintospia?

A

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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