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Psyco 275 > Vision > Flashcards

Vision Flashcards

1
Q

What is light?

A

Discrete particles of energy, photons, or waves of electromagnetic energy

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2
Q

What do we perceive as wavelength?

A

Perception of colour

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3
Q

What do we perceive as amplitude?

A

Perception of brightness or intensity

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4
Q

What are the 3 achromatic colours?

A

Black = produced by lack of light

White = produced by an intense mixture of wavelengths in equal proportions

Grey = produced by a mixture of wavelengths in equal proportions at lower intensities

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5
Q

What are hues/colours?

A

Depend on wavelengths of light that a stimulus or object reflects into the eye
Most objects absorb different wavelengths and reflect the rest

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6
Q

What is the monocular visual field?

A

Visible to one eye

Contains one blind spot

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7
Q

How are monocular visual fields measured?

A

Using perimetry

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8
Q

What is the binocular visual field?

A

Area of overlap between monocular fields

What is seen by both eyes

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9
Q

What is the cornea?

A

Where light first enters the eye
Works with the lens to bend light onto the retina
Cannot change shape

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10
Q

What is the lens?

A

Focuses light onto the retina

Can move

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11
Q

How do we focus on a nearby object?

A

Less tension on ligaments holding lens in place
Holds lens in natural shape
Brings close objects into sharp focus
Loss common cause of presbyopia or hyperopia

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12
Q

How do we focus on a distant object?

A

Increase tension on ligaments holding the lens in place
Flattens the lens
Loss with myopia lens

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13
Q

Where is the site of transduction of light rays?

A

The retina

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14
Q

What are the 5 layers of cells in the retina?

A 
Photoreceptors
Horizontal cells 
Bipolar cells 
Amacrine cells 
Retinal ganglion cells
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15
Q

What are the photoreceptors?

A

Cones and rods

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16
Q

What do horizontal cells and amacrine cells do?

A

Lateral communication

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17
Q

What do retinal ganglion cells do?

A

Axons project on surface of retina

Make up optic nerve

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18
Q

What are 2 disadvantages to the retina inside-out design?

A

Light is distorted

Optic disk has no receptors

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19
Q

How do we fill in the blind spot?

A

Use info from receptors around the blind spot

Surface interpolation

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20
Q

What is the fovea?

A

Tiny indentation in the center of the retina
High acuity vision in the center
Densely packed cones and rod free

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21
Q

What type of vision requires good lighting?

A

The cone vision

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22
Q

What is the photopic system?

A

Provides high acuity coloured perception

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23
Q

What are S-cones?

A 
Short wavelength
Least abundant 
Blue 
High sensitivity 
Less concentrated in fovea
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24
Q

What are M-cones?

A

Medium wavelength

Green

25
Q

What are L-cones?

A

Long-wavelength

Red

26
Q

What is the trichromatic theory of colour vision?

A

3 different colour receptors
Any colour in visible spectrum can be matched by mixing together 3 different wavelengths of light in different proportions
Needs to have at least 3 wavelengths to match every colour

27
Q

What vision is used in dimly lit conditions?

A

Rod vision

28
Q

What is the scotopic visual system?

A

Lacks detail and colours

29
Q

What is the convergence of the scotopic visual system?

A

Several hundred rods converge on one bipolar cell

Poor acuity

30
Q

What happens if you lack rods?

A

Night blindness

31
Q

What is the achromatic vision?

A

Shades of grey from black to white
Not colour sensitive
Do not detect red light

32
Q

What is ON firing?

A

Detect light objects in the dark

33
Q

What if OFF firing?

A

Detect dark objects in light environments

34
Q

What are OFF firing bipolar cells

A

Depolarize when light is off

35
Q

What are ON firing bipolar cells?

A

Depolarize when light is on

36
Q

What cells are inhibited by glutamate?

A

ON firing cells

IPSP

37
Q

What cells are excited by glutamate?

A

OFF firing cells

EPSP

38
Q

Firing in ON center cells?

A

Light in center of receptive field increase firing

Light in periphery of receptive field = off firing inhibition

39
Q

Firing in OFF center cells or ON surround?

A

Increase firing when light is on in the surrounding area of receptive field
Light in the center of the receptive field by decrease firing

40
Q

What are horizontal cells responsible for?

A

Axoaxonic contact of photoreceptors
Acts as an interneuron
Enhances brightness contrast

41
Q

What do ON center and OFF center cells respond best to?

A

Contrast

Most effective way to influence firing is to illuminate entire center and keep entire surround unilluminated

42
Q

What is the geniculate striate pathway?

A

Retina to optic nerve to LGN to striate visual cortex

43
Q

What is the SCN?

A

Control diurnal rhythms, RGC sensitive to blue light

44
Q

What is the superior colliculus?

A

Reflexive eye and head movements

45
Q

What is the pretectum?

A

Pupillary eye reflex

46
Q

What is the LGN?

A

Receives input from the contralateral visual field

Disproportionately large foveal representation in striate cortex

47
Q

What are the parvocellular layers?

A

Projections from small p RGC, more p cells than m cells
Project to top 4 layers of LGN
Responsive to colour, slow moving or stationary details, and fine pattern detail, small receptive field
Input primarily from cones
Project to bottom of striate layer 4 neurons

48
Q

What are the magnocellular layers?

A

projections from big m RGC
Project to the bottom 2 layers of LGN
Responsive to movement, large receptive field
Input primarily from rods
Project to top part of striate layer 4 neurons

49
Q

What is the striate cortex involved in?

A

The initial cortical processing of all visual information necessary for visual perception

50
Q

What does damage to the striate cortex result in?

A

loss of vision in the contralesional hemifield

51
Q

What is scotoma?

A

Damage in one hemisphere in V1

Area of blindness in the contralateral visual field of both eyes

52
Q

What is an opponent-process theory?

A 
2 different classes of cells encode colour and a third that encodes brightness 
Each class encodes 2 complementary perceptions
53
Q

What is the secondary visual cortex?

A

Input mostly from V1

24 subsections

54
Q

What is the association cortex?

A

Prestriate cortex and inferotemporal cortex

55
Q

What is the dorsal stream?

A

Directs behavioural interaction with visual stimuli but not recognition of objects
Perception of where objects are

56
Q

What is akinetopsia?

A

Inability to perceive fluid motion
Unilateral or bilateral MT damage in the dorsal stream
See the world in snapshots
Cannot appropriately control behaviour

57
Q

What is the ventral stream?

A

Mediates conscious perception of objects

58
Q

What is prosopagnosia?

A

Failure of face recognition

Can recognize other objects

Psyco 275 (9 decks)

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