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Neuropsychology > week 4 > Flashcards

week 4 Flashcards

1
Q

what happens if an image stays to long on human retina

A

it disappears

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2
Q

why does the image disappears ?

A

the eye collects change overtime

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3
Q

how long does it takefor an image to fade when stabilised ?

A

10-30 sec

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4
Q

what are the two sources of retinal image motion

A

object move while the eyes are still

objects still, eyes more

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5
Q

explain moving object while the eyes are still work?

A

if the black dot is fixated, the image of of will fall on the fovea but the image of the will move across the retina

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6
Q

Explain still object and eyes move work?

A

fixate on a moving object on the fovea casuing stationary patterns to be swept.

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7
Q

why does the retina move a lot?

A

The retina compensates for our own motion to detect object motion.

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8
Q

What are the three signals telling us about motion?

A

image on retina which motion stream can detect
feedback from extra-ocular muscles
corollary discharge (expected use)

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9
Q

What can we determine from motion sequence?

A

Direction and speed
Direction and speed relative to other objects
relative distance
both animate and rigid objects

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10
Q

In terms of light what does the retina detect?

A

Retina detects the change in light levels overtime.

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11
Q

How is our sensitivity of light measured?

A

It is measured using temporal frequency

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12
Q

What is our overall sensitivity to flicker supported by?

A

Both the M and P pathways

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13
Q

What is Reinhardt detector?

A

Described a way of combining early visual receptive fields to make a direction selective unit

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14
Q

When do humans show direction selectivity in neurones?

A

Cortical area V1 , except for rabies - retina

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15
Q

In regards to Reichardt: motion in the correct direction

A

Stimulates the detector - because the first is delayed they overlap

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16
Q

In regards to Reichardt: motion in the wrong direction

A

Does not stimulate the detector - because they will never going to overall

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17
Q

In regards to Reichardt: Apparent motion is when:

A

two stationary images displaced with the correct separation in time precent motion

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18
Q

In regards to Reichardt: what is aliasing ?

A

pairing the wrong image features over time.

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19
Q

How does aliasing occur?

A

When the respective field don’t match the patterns at time one and two resulting in a different object motion response

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20
Q

How does motion adaption occur?

A

While viewing a constant signal and reduces sensitivity to that pattern.

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21
Q

Where does adaptation occur in the brain?

A

In the cortex

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22
Q

Normally a stationary pattern:

A

Stimulates motion direction detectors equally in all direction

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23
Q

How Representing motion in xt space

A

The speed of the motion can be represented by the slope of the line

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24
Q

What is reverse Phi motion?

A

Reflects a paradoxical motion percept

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25
Q

How does reverse Phi work?

A

sequence alternates in direction of motion after each pair of frame but contrast is inverted every time to the left

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26
Q

What is the first order of sub-systems?

A

Sensitive to variation across the image

27
Q

What is the second-order of sub-system?

A

is sensitive to variation in local contrast and texture

28
Q

What is the Aperture effect:

A

A problem at the first stage of motion detection.

detection of motion in small a receptive field returns ambiguous answer

29
Q

What is intersection of constraints model?

A

A rigid object that moves produces velocity signals at each edge

30
Q

How does V1 detect the motion in regards to the intersection of constraints model?

A

V1 detects the motion at 90˚ to the edge because of the aperture effect.

31
Q

the motion system combines elements of different orientation

A

into a Percocet of rigid motions

32
Q

if the constraint lines don’t cross, then :

A

the system take the average speed and direction of the motions but doesn’t perceive rigid motion

33
Q

What is the barber pole illusion ?

A

the perceived direction changes with orientation

34
Q

what do the streaks in an image mean?

A

signals a possible direction

35
Q

What does grouping mean?

A

Need to combine signals from detectors at different location to get global motion signals.

36
Q

What is the dot motion threshold ?

A

5- 15%

37
Q

what does MST stand for?

A

medial superior temporal

38
Q

What does the MST stage involve?

A

Combines different directions to determine complex motion flows

39
Q

What is induced motion?

A

A failure to fully segment as static stimulus from its moving surround.

40
Q

what does segmentation do in the brain?

A

extracts moving objects from a scene - usually our own movement

41
Q

3D can be used to :

A

Add depth in the flow field

42
Q

there is a flow filed in our retinas that

A

expands outwards as we reach the point we are heading towards

43
Q

what is biological motion ?

A

the Process of motion elements that signals the presence of normal bodily motion

44
Q

What does biological motion require?

A

a prior knowledge of actions

45
Q

What is the pricing stream in humans similar to and which stream?

A

Macaques

in the dorsal stream

46
Q

What is another name for MT (Middle temporal area)?

A

V5

47
Q

What can MT cells determine?

A

The global flow in a motion target

48
Q

What where the two tasks Newsome & Pare used?

A

Global motion - measures coherence levels

Contrast sensitivity - measures contrast needed in grating targets

49
Q

What does remove MT/M5 impair?

A

Impairs GM detection but does affect contrast sensitivity

50
Q

What does the transcrainl magnetic stimulation in humans impact?

A

Motion perception

51
Q

How can MT be detected?

A

fMRI

52
Q

If MT is missing how can signals react the cortex?

A

there are other pathways but they take longer

53
Q

What is evidence for pathways that bypass MT/V5?

A

Poor on Global Dot Motion task in both half visual fields

54
Q

Whats 3D structure from motion ?

A

observer must detect a stricter that varies in depth.

55
Q

Imagine that you are at Niagara Falls, staring at the falling water for a few minutes. When you look away from the water at the crowd of people, the people seem to be floating upward. What phone,enon have you just experienced?

A

Motion aftereffect

56
Q

Which of these brain regions is most specialised for motion processing?

A

Middle temporal area (area V5/MT)

57
Q

What is a rare neuropsychological disorder in which the affected individual has no perception motion?

A

Akinetopsia

58
Q

If you want a motion detector circuit to respond to faster object motions, which changes should you make to the circuit ?

A

Increase the distance between the detects and or decrease the time delay

59
Q

The impression of smooth motion that comes from the rapid alternation of objects appearing in nearby location in rapid succession is:

A

Apparent motion

60
Q

What is the “Aperture problem”

A

Local edge motion seen through a single aperture is ambiguous

61
Q

What is the motion of an object that is defined by changes in contrast or texture, but not by luminance.

A

Second-order motion

62
Q

The motion we interpret as peoplee moving around from a few animated dotes is called _____ motion

A

Biological motion

63
Q

An area of the visual system that receives one copy of the order issued by the motor system when the eyes move is called ?

A

A comparator

64
Q

Suppose you are in a snowstorm and can tell which way the wind is blowing by what percentage of snowflakes are moving in the same direction. What type of motionn is the most analogous to?

A

Coherent or correlated global dot motion

Neuropsychology (12 decks)

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