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Neuropsychology > week 4 > Flashcards

week 4 Flashcards

(64 cards)

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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
How does reverse Phi work?
sequence alternates in direction of motion after each pair of frame but contrast is inverted every time to the left
26
What is the first order of sub-systems?
Sensitive to variation across the image
27
What is the second-order of sub-system?
is sensitive to variation in local contrast and texture
28
What is the Aperture effect:
A problem at the first stage of motion detection. | detection of motion in small a receptive field returns ambiguous answer
29
What is intersection of constraints model?
A rigid object that moves produces velocity signals at each edge
30
How does V1 detect the motion in regards to the intersection of constraints model?
V1 detects the motion at 90˚ to the edge because of the aperture effect.
31
the motion system combines elements of different orientation
into a Percocet of rigid motions
32
if the constraint lines don't cross, then :
the system take the average speed and direction of the motions but doesn't perceive rigid motion
33
What is the barber pole illusion ?
the perceived direction changes with orientation
34
what do the streaks in an image mean?
signals a possible direction
35
What does grouping mean?
Need to combine signals from detectors at different location to get global motion signals.
36
What is the dot motion threshold ?
5- 15%
37
what does MST stand for?
medial superior temporal
38
What does the MST stage involve?
Combines different directions to determine complex motion flows
39
What is induced motion?
A failure to fully segment as static stimulus from its moving surround.
40
what does segmentation do in the brain?
extracts moving objects from a scene - usually our own movement
41
3D can be used to :
Add depth in the flow field
42
there is a flow filed in our retinas that
expands outwards as we reach the point we are heading towards
43
what is biological motion ?
the Process of motion elements that signals the presence of normal bodily motion
44
What does biological motion require?
a prior knowledge of actions
45
What is the pricing stream in humans similar to and which stream?
Macaques | in the dorsal stream
46
What is another name for MT (Middle temporal area)?
V5
47
What can MT cells determine?
The global flow in a motion target
48
What where the two tasks Newsome & Pare used?
Global motion - measures coherence levels | Contrast sensitivity - measures contrast needed in grating targets
49
What does remove MT/M5 impair?
Impairs GM detection but does affect contrast sensitivity
50
What does the transcrainl magnetic stimulation in humans impact?
Motion perception
51
How can MT be detected?
fMRI
52
If MT is missing how can signals react the cortex?
there are other pathways but they take longer
53
What is evidence for pathways that bypass MT/V5?
Poor on Global Dot Motion task in both half visual fields
54
Whats 3D structure from motion ?
observer must detect a stricter that varies in depth.
55
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?
Motion aftereffect
56
Which of these brain regions is most specialised for motion processing?
Middle temporal area (area V5/MT)
57
What is a rare neuropsychological disorder in which the affected individual has no perception motion?
Akinetopsia
58
If you want a motion detector circuit to respond to faster object motions, which changes should you make to the circuit ?
Increase the distance between the detects and or decrease the time delay
59
The impression of smooth motion that comes from the rapid alternation of objects appearing in nearby location in rapid succession is:
Apparent motion
60
What is the "Aperture problem"
Local edge motion seen through a single aperture is ambiguous
61
What is the motion of an object that is defined by changes in contrast or texture, but not by luminance.
Second-order motion
62
The motion we interpret as peoplee moving around from a few animated dotes is called _____ motion
Biological motion
63
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 comparator
64
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?
Coherent or correlated global dot motion

Neuropsychology (12 decks)

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