L4 - Motion

Question 1

What 3 types of perceptual information do we gain from motion?

Answer 1

Figure-Ground Segregation

Extraction of three-dimensional structure

Visual guidance of action

Question 2

How does motion help figure-ground segregation?

Answer 2

When there is camouflaged it is hard to detect, however when it moves it becomes easier to identify.

Question 3

How does motion aid in the extraction of three-dimensional structure?

Answer 3

If something is static you don’t get as good of an idea of it’s volume until it moves

Question 4

How does motion aid in visual guidance of action?

Answer 4

Motion information is crucial when interacting with the environment in order to avoid harming oneself and moving fluently in the world

Question 5

What did Barlow and Levick (1965) discover?

Answer 5

Neurons that are responsible for motion.

Question 6

What happens to the motion neuron if a stimulus in the visual field of a neuron is moving in the preferred direction?

Answer 6

You get an increase in the response of the neuron.

Question 7

What happens to the motion neuron if a stimulus in the visual field of a neuron is moving in the null direction?

Answer 7

You get no change in response.

Question 8

Why was Barlow and Levick’s discovery of motion neurons a big deal in psychology?

Answer 8

It showed that there is a direct relationship to what is happening in the brain in response to the environment.

Neurons were coding movement in the world.

Question 9

Are cells in the retina directionally selective?

Answer 9

Yes

Suggested building block for motion

Question 10

What is directional tuning?

Answer 10

Humans can detect all orientations of movement through many specific neurons.

Question 11

How might you model motion detection?

Answer 11

Have a stimulus that changes its location over time and record responses at different locations.

T1->T5 (bottom left) is stacking on top of one another. If we do this we get orientation in space and time.

T1 = time 1 etc.

Question 12

What is a simple motion detection unit in the brain?

How does it work?

Answer 12

A comparator neuron

It has two input signals, one of which is delayed. If a stimulus is moving in one direction the delayed receptor and the normal receptor will reach each other at the same time, indicating movement in a certain direction.

Question 13

Who proposed the simple motion detection unit model?

What does it allow you to do?

Answer 13

Reichardt (1961) (From his work analysing flies)

Allows you to detect the difference in motion between A and B

Question 14

We can think of motion as orientation in _____ and _____.

Answer 14

Space and Time

Question 15

Who proposed the Energy Model?

Answer 15

Adelson and Bergen (1985)

Burr, Ross and Morrone (1986)

Question 16

Which model is this?

How does it work?

Answer 16

Reichardt model

Question 17

Which model is this?

How does it work?

Answer 17

Energy Model

Question 18

What is the extra stage in the energy model compared to the Reichardt model?

Answer 18

Oriented Linear Response

Question 19

What does the Oriented Linear Response allow us to do in the energy model?

Answer 19

Allows us to aggregate information for motion in space and time.

Question 20

What are the 3 benefits of the energy model?

Answer 20

No need to discrete correspondence (allows us to aggregate over more instances, if our filters don’t quite match the aggregation makes movement easier to catch)

Specificity: Motion response is to a particular space, time and spatial frequency.

More flexible definition of a feature: Ability to detection motion in random noise patterns

Question 21

What is the Aperture problem (barber pole illusion)?

Answer 21

The grading is moving from left to right, however, the bars look like they are moving up and down.

It looks like it changes direction depending on the orientation of the aperature

Question 22

Why does the Aperture problem exist?

Answer 22

The motion of a repetitive pattern is essentially featureless.

Question 23

What is meant by local vs global features in regards to the Aperature problem?

Answer 23

Local receptive fields (motion detectors in the retina) do not have enough information to disambiguate direction of the object’s motion.

In order to disambiguate the information, we use the orientation information of the edges of the aperture to determine the direction (global).

This is why changing the shape of the aperture will make the lines seem like they are moving in a different direction.

Question 24

Do you get the barber pole illusion if the motion information if you use a non-repetitive pattern?

Answer 24

No, because it has features you will be able to determine the correct direction of motion.

Question 25

What does 'pooling of information' mean in regards to disambiguating motion direction?

Answer 25

We can't use just local information if the moving formations are featureless. Therefore we pool **'movement' information** and the **'form' information** to generate a sense of direction.

Question 26

What are 3 tools we use to disambiguate direction?

Answer 26

Line endings *(where the line ends)* Form information from the edges of the aperture Global pooling of local information

Question 27

What is the average integration time for cells in V1?

Answer 27

100ms *They collect information over 100ms before they make some kind of response*

Question 28

How does the delay in V1 cells help us disambiguate motion direction?

Answer 28

Through detecting a blur, then by filtering it using a **motion deblurring mechanism**.

Question 29

How did Geisler (1999) test the V1 motion deblurring theory?

Answer 29

Showing stimulus in two different directions and adding 'noise' to see if it interferes with the performance

Question 30

How do we use motion streaks to detect motion?

Answer 30

If you are moving along you have orientation information and you are also getting orientation information along the axis of that (with a slight delay from V1) and you can use that to disambiguate motion.

Question 31

Can we use form information alone to generate a perception of coherent global motion? How was this demonstrated?

Answer 31

Yes Showed using Glass patterns: series of points on a screen randomly and you apply a rule (e.g. be radial) - No one dot is the same but because there is a global rule they see motion.

Question 32

What part of the brain does 'glass' patterns activate? What does this imply?

Answer 32

MT/V5 (for motion) Implies that our brain sees the individual dots as motion.

Question 33

What did Albright, 1984 discover about cells in MT?

Answer 33

They are sensitive to the direction of motion, but also orientation and pattern information.

Question 34

Does orientation information contribute to perceived motion direction?

Answer 34

Yes

Question 35

What did Johansson (1963) demonstrate? What is this called?

Answer 35

That people are able to recognise people walking, even when there are only points of light on the joints. **Biological Motion**

Question 36

What does **Biological Motion** suggest about how our brain processes movement information?

Answer 36

That there is a high-level constraint on low-level information. *We pool our low-level information and combine it with high-level information we have about form to see biological motion*