L3 - Spatial Vision

Question 1

What is Spatial Vision?

Answer 1

How you see things in space.

What are the things you see in space around you.

Question 2

Who was David Marr? What did he publish?

Answer 2

Trained as an electrophysiologist and a computer scientist.

Published a book called ‘Vision’ (1980)

Question 3

What were the 3 stages of vision that Marr suggests that we see vision?

Answer 3

Primal Sketch: Sparse Representation of local features

2.5D Sketch: Shape Representation

3D Sketch: Object Representation

Question 4

What is a Receptive Field?

Answer 4

The particular region of the sensory space (e.g. body surface, or visual field) in which a stimulus will modify the firing of that neuron.

When you present information the neuron changes its firing rate​

Question 5

What happens to receptor fields (area over which neuron changes its firing rate) as they go ‘up’ the visual systems?

Answer 5

These get bigger as they go up cortex.

By the time they go up to the highest level of cortex they are up to a quarter of your visual field

Question 6

What is a Primal sketch according to Marr?

Answer 6

You just have little bits of the object, a couple of contours. Not the full outline of a shape just sparse parts.

Question 7

What is a 2.5D sketch according to Marr?

Answer 7

It’s a representation that suggests that there is a contour that can do something but you do not yet have the whole object.

Not fully formed

Question 8

What is a 3D sketch according to Marr?

Answer 8

When you put all the contours together you get a whole object and it is fully formed.

Question 9

Describe Hubel and Wiesel’s Simple Cells.

Answer 9

They are orientation selective.

Have an elongated retinal receptive field containing excitatory and inhibitory zones.

Question 10

Describe Hubel and Wiesel’s Complex Cells.

Answer 10

They have a relatively large receptive field.

Does not contain identifiable excitatory or inhibitory zones.

It is orientation selective (not as much as simple cells)

Question 11

What is information that increases the firing rate of a neuron called?

Answer 11

Excitatory

Question 12

What is information that decreases the firing rate of a neuron called?

Answer 12

Inhibitory

Question 13

What does elongated mean?

Answer 13

To make (something) longer, especially unusually so in relation to its width.

Question 14

Does the orientation of a stimulus matter more for simple cells or complex cells?

Answer 14

Simple cells react differently to different orientation whereas complex cells generally don’t.

The lines indicate activation and at what time.

Question 15

Are human being equally sensitive to all contrasts?

Answer 15

No.

As the background changes it makes it more difficult to see differences in contrast.

Question 16

1. What is Spatial Frequency?
2. What is Spatial-Frequency Theory?

Answer 16

1. The spatial frequency is expressed as the number of cycles per degree of visual angle.
2. That the visual cortex operates on a code of spatial frequency.

Question 17

Is the peak sensitivity for human contrast at a high, low or mid-range frequency?

Answer 17

Our peak sensitivity is at a mid-range of spatial frequency.

Question 18

What are the 4 principles of Gestalt Laws?

Answer 18

They argued that we use -

Proximity

Similarity

Common fate

Good Continuation

In order to help organise information

Question 19

What is Gestalt’s Law of Proximity?

Answer 19

We use proximity to group things together.

If there are 6 dots and 3 are close to one another, we will group those 3 each into individual groups.

Question 20

What is Gestalt’s Law of Similarity?

Answer 20

When separating objects into groups we typically group objects that are similar to one another together.

Question 21

What is Gestalt’s Law of Good Continuation?

Answer 21

Parts that flow together neatly (have continuous edges) are typically grouped together.

Boundary is likely to be a smooth contour.

Question 22

What is Object Invariance?

Answer 22

Humans are able to recognise something as the same type of object, even though the individual items have different attributes.

• You can see something is a bird even if you’ve never seen that type of bird before*
• Some sort of flexible template?*

Question 23

Describe Haushofer and Kanwisher’s theory of Object Recognition.

Answer 23

There is a specialised region within the brain for distinct categories.

Different areas for faces, houses etc.

Question 24

Describe Habak, Wilkinson, Zakher and Wilson’s theory on Object Recognition.

Answer 24

It is a bottom-up process that can be thought of in terms of spatial filtering.

Low-level vision, we are constantly doing spatial frequency analysis.

Question 25

What does the Face Adaptation theory suggest?

Answer 25

That humans have a special ‘face space’ in the brain - the fusiform face area (FFA) that is specialized for facial recognition.

Question 26

Children can identify faces in objects from a very young age.

True or False

Answer 26

True

We seem to have innate ability to detect faces from a very young age (biological advantage perhaps)

Question 27

Human beings are just as good at recognizing bits of a face as we are at recognizing a whole face

True or False

Answer 27

False

We struggle to recognize parts of a face and put it to a person.

Question 28

If you look at an angry face then look at a neutral face you are more likely to perceive the face as a -

Neutral Face

Happy Face

or Angry Face?

Answer 28

Angry Face, it seems as though our interpretation follows over somehow.

Question 29

Prosopagnosia is?

How is it acquired?

Answer 29

The inability to recognise faces.

Through brain trauma, stroke or degenerative disease. Can be congenital.

Question 30

Capgras syndrome is?

How is it acquired?

Answer 30

Inability to recognise the identity of a person.

Acquired as a result of brain trauma, stroke or degenerative disease. Can be congenital.