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PSYC255 > Vision > Flashcards

Vision Flashcards

1
Q

What do sensory receptors do?

A

Convert stimuli into useable information

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2
Q

What do vision/audition/somatosensory sensory receptors do?

A

Vision (light waves to chemical energy)
Audition (sound waves to mechanical energy)
Somatosensory (touch and pressure to mechanical energy)

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3
Q

Sensation

A

Registration by the sensory organs of physical stimuli from the environment

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4
Q

Perception

A

Subjective interpretation of sensations by the brain

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5
Q

Retina

A

Light-sensitive surface at the back of the eye consisting of neurons and photoreceptor cells

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6
Q

Fovea

A

Central region of the retina specialized for high visual acuity

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7
Q

Blind spot

A

Retinal region where axons forming the optic nerve leave the eye and where blood vessels enter and leave - No Photoreceptors!

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8
Q

Rod

A

Photoreceptor specialized for functioning in low light

Scotopic (active in low light, inactive in bright light)
Sensitive to small changes in brightness
Low acuity
Insensitive to colour/detail
High convergence of info to ganglion cells

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9
Q

Cone

A

Photoreceptor specialized for colour & high visual acuity

Photopic (inactive in low light, active in bright light)
Insensitive to small changes in brightness
High acuity
Sensitive to colour/detail
Low convergence of info to ganglion cells

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10
Q

What is the wavelength range of electromagnetic radiation that is visible to the human eye?

A

About 400 to 700 nm
400 (deep purple)
700 (red)

Violet < Blue < Green < Yellow < Orange < Red

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11
Q

Retinal neurons

A

Bipolar cell
Horizontal cell
Amacrine cell
Retinal ganglion cell (RGC)

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12
Q

Bipolar cell

A

Receives input from photoreceptors

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13
Q

Horizontal cell

A

Links photoreceptors and bipolar cells

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14
Q

Amacrine cell

A

Links bipolar cells and ganglion cells

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15
Q

Retinal ganglion cell (RCG)

A

Gives rise to optic nerve

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16
Q

Two (primary) visual pathways

A

Geniculostriate system
Tectopulvinar system

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17
Q

Tectopulvinar system

A

Projections from the retina to the superior colliculus to the pulvinar (thalamus) to the parietal and temporal visual areas

18
Q

Geniculostriate system

A

Projections from the retina to the lateral geniculate nucleus (LGN of thalamus) to the visual cortex (V1; BA17)

19
Q

Parvocellular cell (P layers)
[Geniculostriate Pathway]

A

(Parvo- = small)
Receives input mostly from cones
Sensitive to colour

20
Q

Magnocellular cell (M layers)
[Geniculostriate Pathway]

A

(Magno- = large)
Receives input mostly from rods
Sensitive to light and moving stimuli

21
Q

Describe the geniculostriate pathway

A

Info travels from right side of each retina to right LGN

Info from contralateral side goes to layers 1, 4, 6
Info from ipsilateral side goes to layers 2, 3, 5

Layers 1 and 2 receive inout from magnocellular pathway
Layers 3 - 6 receive input from parvocellular pathway

22
Q

What does V1 refer to?

A

Striate cortex (heterogenous, processing different information)

23
Q

Visual pathways beyond the occipital lobe

A

Ventral stream
Dorsal stream

24
Q

Ventral stream

A

“What” pathway
Pathway to the temporal lobe
Recognizing objects; global features vs. one feature

Recognize things

25
Q

Dorsal stream

A

“Where/how” pathway
Pathway to parietal lobe
Sensitive to movement
Spatial ability

Where in space
How do I interact with them

26
Q

Describe the receptive-field hierarchy

A

(moving from eyes to brain)

Receptive fields of many retinal ganglion cells:
Combine to form a receptive field of a single LGN cell:
The receptive fields of many LGN cells combine to form the receptive field of a single V1 cell

27
Q

Where are the central/peripheral/top areas of the visual field represented in the brain?

A

Central = back of the brain
Peripheral = more anteriorly
Top = lower part of occipital

28
Q

Different types of neurons throughout the visual system

A

Retinal ganglion cells
Primary visual cortex
Temporal cortex

29
Q

Retinal ganglion cells (RGC)

A

Shape is contructed in cortex from info from RGCs

RGCs do not detect shape, only light

Receptive field of a ganglion cell is concentric circles
- on-centre, off-centre

30
Q

Luminance contrast

A

Amount of light an object reflects relative to its surroundings

  • A ganglion cell tells the brain about the amount of light hitting a certain part of the retina relative to the average amount of light hitting the rest of the retina
31
Q

What do RGCs send info regarding?

A

Send info about edges

The info from RGCs sent to the visual areas of the brain are not treated equally from all visual field regions
- Regions that have differences in luminance (areas along edges) are emphasized (edges form shapes)

32
Q

How are shapes processed in V1?

A

Each V1 cell receives inout from several RGCs
Orientation detectors - maximally responsive to orientation of bars of light

33
Q

Simple cells (V1)

A

On-off receptive field arrangement

34
Q

Complex cells (V1)

A

Receptive fields maximally excited by bars of light moving in a particular direction

35
Q

Hypercomplex cells

A

Receptive fields maximally excited by moving bars of light (like complex) but also have a strong inhibitory area at one end of the receptive field

36
Q

When does simple cell/complex cell/hypercomplex cell fire?

A

Simple: if light is along its “on” receptive field
Complex: if stimuli is at a certain angle to its circular receptive field
Hypercomplex: horizontal, moving light in its “on” receptive field

37
Q

Stimulus equivalence

A

Recognizing that an object is the same across different viewing orientations

38
Q

In terms of processing shapes in temporal cortex, what are the cells maximally excited by?

A

Complex visual stimuli (like faces)

Temporal lobe = less hard wired, more flexible

39
Q

Trichromatic theory

A

Explanation of colour vision based on the coding of the primary colours: red, green, and blue
- colour we see if determined by the relative responses of the different cone types
- if all active, we see white
- explains colour blindness/deficiencies

40
Q

Opponent processing

A

Explanation of colour vision that emphasizes the importance of the opposition of colours
- The beginning of colour processing in the cones follows trichromatic theory, opponent processing occurs afterwards

41
Q

Colour constancy

A

The ability to perceive the colour of an object as remaining the same, even when the lighting changes

(bowl of fruit and green glasses example)

PSYC255 (10 decks)

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