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Perception Block 10 > Temporal Vision > Flashcards

Temporal Vision Flashcards

1
Q

Concerned with changes in luminance across space

A

Spatial vision

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2
Q

Concerned with changes in luminance over time

A

Temporal vision

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3
Q

What is the peak of the sinusoid deal wave called

A

Modulation depth, amplitude, contrast

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4
Q

The stimuli whose luminance caries sinusoidally over time

A

Temporal sinusoids

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5
Q

A temporal sinusoid manifests sinusoidal changes in luminance over _______

A

Time

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6
Q

Modulation depth changes with respect to _____

A

Time

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7
Q

At what modulation depth is it more steady

A

Low modulation depth

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8
Q

What modulation depth is there more flickering

A

High modulation depth

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9
Q

A temporally modulated stimulus of a low modulation depth, as in may not be resolved, appearing ______

A

Steady

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10
Q

As the modulation depth increased, however, it may be resolved and seen as _______

A

Flickering

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11
Q

Rate of change of frequency with time

A

Temporal frequency

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12
Q

Low temporal frequency stimulus may be seen as a _____ at a low rate

A

Snickering at a low rate

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13
Q

A higher temporal frequency stimulus may appear to _____ at a higher rate

A

Flicker

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14
Q

Temporal frequency is typically given in

A

Hertz

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15
Q

Modulation depth and temporal frequency in slow flicker

A

Low for both

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16
Q

For a fast flicker, what is the modulation depth and temporal frequency

A

High

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17
Q

As the temporal frequency is increased, a frequency is reached at which flicker can no longer be resolved at that frequency, is called the

A

Critical flicker fusion frequency (CFF)

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18
Q

A frequency is eventually reached that cannot be resolved, and the stimulus appears

A

Steady

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19
Q

This temporal frequency that appears steady, the CFF, represents the _________ of the visual system for a given modulation depth

A

The high temporal resolution limit

Temporal acuity

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20
Q

The CFF increases _____ with the log of the retinal illumination

A

Linearly

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21
Q

CFF is considered _____ under photopic compared to scotopic conditions

A

Higher

Due to a general speeding up of retinal processes that occurs at increasing levels of light adaptation

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22
Q

If you increase retinal illuminate, what happens to CFFF

A

Increases linearly

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23
Q

How do you determine temporal MTF

A
  • views stimulus at given temporal rate
  • modulation depth small first and the screen appears steady
  • the modulation depth is slowly increased until the subject reports screen is flickering
  • the modulation depth at which the subject first sees flicker is threshold
  • its reciprocal is relative sensitivity for flicker resolution
  • repeated for a large number of temporal frequency
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24
Q

The modulation depth is slowly increased until the subject reports the screen ________

A

Flickering

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25
Q

The modulation depth at which the subject first sees flicker is the

A

Threshold

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26
Q

The reciprocal of the modulation depth at which the subject first sees flicker is the

A

Relative sensitivity

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27
Q

Stimuli that fall outside of the TMFT are seen as fused or steady; they are not ___________ temporally

A

Resolved

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28
Q

Those stimuli that fall under the graph are _________ and perceived as flickering

A

Resolved temporally

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29
Q

TMTF show maximal sensitivity to __________ frequencies

A

Moderate

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30
Q

For the TMTF, the high frequency cutoff represents the highest temporal frequency that can be

A

Resolved at 100% modulation

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31
Q

Larger stimulus in CFF

A

Larger stimulus increases CFF

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32
Q

CFF increases with the log of the ________ area

A

Stimulus

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33
Q

Receptor field size and eccentricity effecting temporal properties

A

Temporal properties of the retina are similar across eccentricity

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34
Q

What are the things that have to happen for the temporal properties to be similar across eccentricity

A

The stimulus size needs to increase to match the size of the ganglion receptive field size, the field increases for ganglion in the periphery

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35
Q

Stimulus which appears steady in the central vision may appear flickering in the periphery due to the ________ of the peripheral retina, for higher luminance

A

Higher temporal resolution

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36
Q

What is temporal acuity better in the periphery

A

When enough luminance which means a much larger stimulus size

37
Q

What about the peripheral retina is important for increased temporal acuity?

A

The number of ganglion are decreased in the periphery, but they have a large reception even field. Stimulus size has to match the receptive field

38
Q

Flicker light and retinal blood vessels

A

May cause dilation of the them, which is localized to the stimulated area due to the response to local metabolic demand

39
Q

Infants ability to resolve temporal stimulus

A

Decreased

40
Q

In the TMTF curve, the reduction in low frequency temporal sensitivity tells us ______ changes in illumination are not seen

A

Very gradual

41
Q

Example of troxler phenomenon

A

Observe the minute hand on a watch, although we know the minute hand moves, we do not actually see it move

42
Q

The manifestation of the visual systems reduced sensitivity to low temporal frequencies is the inability to perceive stationary or stabilized retinal images, called the

A

Troxler phenomenon

43
Q

When we look at a picture that has the X in the middle and a fuzzy gray border, what happens and what is that an example of

A

When looking at the X, the borders disappear

The changes in retinal illuminated are of a very low temporal frequency. Because we are not sensitive to low temporal frequencies, the border disappears

44
Q

When looking at the gray box with the X in the middle and the borders are very distinct, what is happening and why

A

Eye movements across sharply focused borders result in the introduction of moderate temporal frequencies. Because we are sensitive to these frequencies, the border does not disappear

45
Q

When looking at a target, does the eye move or stay still

A

Even when fixating a target, small involuntary eye movements occur continuously

46
Q

Lateral inhibition

A

The receptive field center and surround have different signs

The center and the surround also respond with different latencies

47
Q

Latenices of the center and the surround of a receptive field

A

They are different. There is a phase lag between the center and the surround

48
Q

For low temporal frequencies, their ______ can cause the center and surround signals to cancel each other, thereby reducing sensitivity

A

Phase lag

Response of stimulus in each center and surround happen at differnt times. This is called the phase lag. For low frequencies they cancel each other out after a second

49
Q

What is the low frequency cut off caused by

A

Phase lag

50
Q

What is the high frequency cut off due to

A

Neural constraints

51
Q

Neural constraints in the high frequency TMTF cut off

A

The faster a neural system respond, and the more transient its response, the greater its temporal resolution

52
Q

Why does the neural response limit the high cut off freqncy

A

It is neither fast nor transient enough to allow resolution

53
Q

This provides information regarding both spatial and temporal processing of visual information

A

Masking

54
Q

This reduced the visibility of a stimulus referred to as the target

A

Mask

55
Q

What kind of testing is masking used in

A

Psychophysical (subjective) testing

56
Q

What is forced choice

A

Patient must respond to certain stimulus to get to the next stimulus

57
Q

Types of visual masks

A

Simultaneous masking
Backward masking
Forward masking

58
Q

Both the mask and target are present at the same time

A

Simultaneous masking

59
Q

What is this an example of: a spatial grating (the mask) may interfere with the detection of a stimulus composed of a similar frequency (the target)

A

Simultaneous masking

60
Q

In simultaneous masking, since both the mask and target may share the same spatial frequency channels, there is a

A

Reduction in the visibility of the target gratings

61
Q

What kind of masking is more pronounced in amblyopes

A

Simultaneous

62
Q

Which is better to measure VA for an amblyope, standard eye chart or isolated optotypes

A

Isolated

63
Q

The reduction in acuity caused by surrounding spatial patterns is sometimes referred to as the

A

Crowding phenomenon

64
Q

Examples of crowding examples

A

Letters inside circles and squires.

Flanking rings/optptypes

65
Q

The target precedes the mask

A

Backward masking

66
Q

When does backwards masking occur

A

When the mask is substantiallt brighter than the target, presumably enabling the masks neural response to reach central visual areas first, thereby interfering with detection of the target

67
Q

A form of backward masking where the mask and target are spatially adjacent. The visibility of a briefly presented target is reduced by the subsequent presentation of a spatially adjacent mask

A

Metacontrast
Target first, then mask placed side by side
Lateral inhibition plays

68
Q

_____ within the retina is though to contribute to metacontrast.

A

Lateral inhibition

69
Q

The mask precedes the target. Reduces the visibility of the subsequently presented target

A

Forward masking

70
Q

Type of forward masking where the target and mask are spatially adjacent is referred to as _______. The mask reduced the visibility of a subsequently presented, spatially adjacent target

A

Paracontrast

71
Q

A high temporal frequency tumulus may appear flickering at _____ rate

A

Higher

72
Q

Temporal frequency is given in hertz, 1 Hz is

A

1 cyl/s

73
Q

The CFF for scotopic conditions is ______compared to photopic conditions

A

Lower

74
Q

When testing under scotopic conditions, CFF is expected to be closest to

A

20Hz

75
Q

The CFF for a given percentage modulation is 50Hz. A stimulus of 55Hz, presented at this given percentage modulation is seen as

A

Steady

76
Q

Beyond CFF, the stimuli appears steady because

A

It cant be resolved

77
Q

As the area of the stimulus increases, the CFF ______

A

Increases

78
Q

The detection of high temporal frequency is limited by

A

Speed of measure processing

79
Q

The reduction in sensitivity to low temporal frequencies is caused by

A

Lateral inhibition (phase lag)

80
Q

What prevents our visual world from disappearing when we fixate on object?

A

Small, inhibitory eye movements

81
Q

When the modulation depth very small, the screen appears

A

Steady

82
Q

A maximal TMTF value of a young healthy eye is

A

10Hz

83
Q

At which of the following temporal frequencies does the TMTF sho max sensitivity

A

Moderate

84
Q

When flickering light falls on the retina, nearby blood vessels

A

Dilate

85
Q

The VA of amblyopia patients is poorer when measured using Snellen acuity chart than when measured with isolated optotypes because of

A

Simultaneous masking

86
Q

When a mask reduces sensitivity to previously presented spatially adjacent stimulus, the phenomenon is referred to as

A

Meta contrast

87
Q

When optotypes are surrounded by spatial patterns, the VA ____

A

Decreases

88
Q

Schizophrenia and masking

A

Large amounts of deficits with masking

  • used MRI to test how long the signal took to get from eyes to occipital love
  • backwards masking was used
  • neural problems for masking deficits
89
Q

TMTF and glaucoma

A

Better to test for glaucoma than VF

-good for ARMD and RP too

Perception Block 10 (3 decks)

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