Vision Flashcards

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1
Q

Three steps from stimulus to perception

A

Reception, transduction, coding

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2
Q

Light

A

Adequate stimulus for vision. Described as a particle of energy wave of energy (e-magnetic energy)

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3
Q

2 properties of light

A
  1. Wavelength = color

2. Intensity= brightness

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4
Q

Wavelengths of light (violet-Red) based on rainbow

A

400-700

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5
Q

Pupil

A

Where Light enters the eye.

Size changed in response to changes in illumination

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6
Q

Sensitivity

A

Ability to see when light is dim

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7
Q

Acuity

A

Ability to see details

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8
Q

Lens

A

Focuses light on the retina

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9
Q

Ciliary muscles

A

Alter the shape of the lens as needed

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10
Q

Accommodation

A

Process of adjusting the lens to bring the images into focus

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11
Q

Blind spot

A

No receptors where info exits the eye

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12
Q

Completion

A

Visual system uses info from cells around the blind spot to fill in blind spot (completion)

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13
Q

Fovea

A

High acuity area at center of retina

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14
Q

Thinning of ganglion cell layer…

A

Reduces distortion due to cells between The pupil and the retina

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15
Q

Duplicity theory of vision

A

Cones and rods mediate different kinds of vision

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16
Q

Cones

A

Photopic (daytime vision)

High acuity color info in good lighting

Only cones found in fovea

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17
Q

Rods

A

Scotopic (nighttime vision)

High sensitivity, allowing low acuity vision in dim light. Lack detail and color info.

More convergence. Increasing sensitivity while decreasing acuity.

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18
Q

Visual transduction (in light) step 1

A

Light bleached rhodopsin molecules

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19
Q

Visual transduction (light) step 2

A

Sodium channels close

20
Q

Visual transduction (light) step 3

A

Sodium ions cannot enter rods = rods hyperpolarized

21
Q

Visual transduction (light) step 4

A

Glutamate release is reduced

22
Q

Trichromatic theory of color vision

A

3 different kinds of cones

  1. Short wavelength: blue
  2. medium wl: green
  3. long wl: red and yellow

Discriminate among wavelengths by ratio of activity across 3 types

Intense light increases activity of all 3 but ratio of responses stays same

23
Q

Opponent process theory

A

2 different classes of cells in the visual system for encoding color and another one for encoding brightness

Hering: each of 3 cells encoded 2 complenatry color perceptions

1class= signaled red by changing activity in one direction (ex:depolarization and hyperpolarization)

2class= signal blue and yellow in same opponent fashion.

24
Q

Evidence to support opponent process

A
  1. If state at something yellow for 1 minute and look at white = see blue. (Same for is u stare at red, green = green, red) afterimage
  2. cells in lateral geniculate nucleus may be excited by green light and inhibited by red light.
25
Q

Blue yellow color deficiency

A

Very rare

26
Q

Red-green color deficiency

A

Most common

^ due to deficient cone that process that colors wavelength

27
Q

Protanopia

A

Red weak

Brightness of red. Orange. And yellow is reduced. Shift to appearing green

28
Q

Deuteranopia

A

Green weak

Same perceptual problem with red. Orange. Yellow. green brightness reduced. Shift to see red.

29
Q

Receptive fields

A

Portion of retina in which light affects the activity of a given neuron

Light in retinal area leads to excitization or inhibition of cortical cell

30
Q

Define receptive fields in 2 ways

A

An area of retina

An area of visual field

^ equivalent

31
Q

Left visual field reaches…

A

Right primary visual cortex

Vice versa for Right visual field

32
Q

Similarities seen at all three neurons (retina,geniculate,striate)

A

Receptive fields in fovea smaller than periphery

Neurons receptive fields are circular

Neurons Monocular

Many neurons with excitatory and inhibitory area.

33
Q

Retinoptopic organization

A

(Striate system)

Info received at adjacent portions of retina remain adjacent in straite

More cortex is devoted to areas of high acuity

25% of primary visual cortex is dedicated to input from fovea

34
Q

Magnocellular layers

A

Big cell bodies (bottom two layers of LGN)

Responsive to movement

Input from rods

35
Q

Parvocellular layers

A

Small cell bodies, top 4 layers of LGN

Color, detail and still/slow objects

Input from cones

36
Q

Visual cortex organization

A

Lateral geniculate area -> primary visual cortex (V1)-> secondary visual cortex (V2)-> association cortex

37
Q

Parallel processing

A

Info flow through components over multiple pathways

Combined activity of many interconnected cortical and subcortical areas of each sensory system

38
Q

V1+V2

A

Feature detectors: neurons respond to presence of a particular feature

Spatial frequencies

39
Q

Inferior temporal cortex

A

Large receptive fields

Detailed info about stimulus shape

40
Q

Posterior parietal cortex

A

Spatial attention: where in space stimulus allocated

Spatial neglect: ignore one power of body or extrapersonal space

41
Q

Visual agnosia

A

Inability to recognize objects

42
Q

Prosopagnosia

A

Inability to recognize faces. Able to read and write and reocgnize other objects.

Trouble recognizing different kinds of animals and cars.

Difficulty with complex visual discriminations

Evidence from brain imaging studies in normals: objects and faces processed by central stream.

43
Q

Middle temporal cortex (MT) (V5)

A

Motion perception info is processed

44
Q

Medial superior temporal cortex (MST) (V4)

A

Motion perception info is processed

45
Q

Motion perception

A

Cells respond selectively to speed and direction of movement

46
Q

Disorders of motion perception monkeys…

A

Monkeys with damage to MT or MST respond inaccurately to moving visual stimuli

47
Q

MT damage in humans

A

Causes motion blindness