Lecture 14 - Object Recognition: From Objects to Faces

Question 1

What is one of the main benefits of having two eyes?

Answer 1

Two eyes means that we can have a perception of depth.

Question 2

What is Marr’s theory of Recognition?

Answer 2

Marr’s theory of Recognition looks at the brain as behaving like a computer (computational model), developing algorythms that allow for recognition.

Question 3

Marr’s theory of Recognition says that one of the first stages of recognition is the recognition of EDGES.
This recognition of edges occurs at the level of the retina and the LGN.
‘Edge’ detectors are receptive fields that are sensitive to light discontinuity - characteristic of edges.

True or false?

Answer 3

True.

Question 4

At the level of the Primary Visual Cortex (V1) there are orientation receptive fields.
True or false?

Answer 4

True.

Question 5

What occurs at the level of V4 in the visual cortex?

Answer 5

Neurons in the V4 are receptive to curvature and shape in the light signals being received by and transferred from the retina.

Question 6

What does “viewer-centred” representation mean?

Answer 6

Viewer-centred

Question 7

What is the role of the Inferior Temporal Cortex in object recognition?

Answer 7

Development of a robust perception of the light signals that are

Question 8

Recognition of objects requires prior experience/learning and memory.
This means that object recognition requires not only the visual cortex, but connections to other areas of the brain.
True?

Answer 8

True.

Question 9

Is processing of light signals in the Inferior Temporal Cortex viewer-dependent?

Answer 9

No. The processing and reconstruction of light signals at the level of the Inferior Temporal Cortex is a more robust representation of what we are actually “seeing” and is less affected by movement or changes in direction of the visual field - this means we can still recognise something even if we or it moves.
This is not the case for the processing of signals that occurs at V1 and V4.

Question 10

What is the Ventral Stream?

Answer 10

In regards to visual processing the ventral stream stream is known as the “What” pathway for object recognition.

Question 11

There is evidence that suggest modularity of the visual cortex when it comes to areas that are more involved in the recognition of certain types of objects, such as the Fusiform Face Area.
True or False.

Answer 11

True.

Question 12

What is visual agnosia?

Answer 12

Visual Agnosia is the inability to recognise objects. This is often seen in individuals who have lesions or damage to the Inferior Temporal Cortex. The extent of a person’s visual agnosia in these cases in dependent on the size of the lesion, which lends evidence to the idea of modularity of this brain area in regards to object recognition.

Question 13

Humans are very good at recognising faces compared to other objects.
True or false?

Answer 13

True.

Question 14

There are neurons in the Inferior Temporal Cortex that are more active in response to faces and configurations that look like faces.
True or false?

Answer 14

True.

Question 15

What is prospagnosia?

Answer 15

Prosopagnosia is the inability to recognise faces.

Question 16

The brain is also able to recognise contexts and scenes, aka scene recognition. What area is responsible for scene recognition?

Answer 16

The Parahippocampal Place Area.

Question 17

What is the “inversion” effect?

Answer 17

The inversion effect refers to our inability to recognise faces and scenes as well if they are upside down/inverted. as we normally see faces or scenes upright.

Question 18

The brain is able to store a large amount of visual information from scenes with high fidelity even if the exposure to this scene is brief and there are many other competing scenes.
True or false?

Answer 18

True.

Question 19

Is object recognition a precursor for scene recognition?

Answer 19

No. Scene recognition can still be in tact even if there is damage to the Inferior Temporal Cortex (Area for object recognition).

Question 20

Where in the brain does evidence suggest scene recognition occurs?

Answer 20

Scene recognition is postulated to occur in the Parahippocampal Place Area (PPA).

Question 21

What is a hemianopic field?

Answer 21

Hemianopia is the loss of vision in half of the visual field in one or both eyes. Most commonly caused by a stroke.

Question 22

What is blindsight?

Answer 22

Blindsight refers to the unconscious processing of visual information, such as knowing an object moved, but not “seeing” it move, if you have a certain cortical blindness.

Question 23

What is the first thing that is required in object recognition, according to Marr?

Answer 23

EDGE recognition. Edge-sensitive receptive fields are found initially in the LGN.

Question 24

Orientation coding at the level of V1 allows for the detection of edges and their continuity or discontinuity, according to Marr.
True?

Answer 24

True. At V1 we are processing information not just information about whether there was an edge, but also what orientation the edge has.

Question 25

In what area of the visual field are there neurons that are sensitive to surface shapes, such as curvature?

Answer 25

There are neurons in V4 that are sensitive to curvature and surface shapes.

Question 26

At the level of V4 the information is viewer-centred. What does this mean?

Answer 26

Information that is viewer -centred means that we are processing information about what we are seeing in the moment from our perspective. We need a viewer-independent perspective to be able to recognise objects, as they look different from different perspectives. Does this happen in the Inferotemporal area? FFA? Yes.

Question 27

Where does specific object recognition occur?

Answer 27

In the inferotemporal/inferior temporal cortex.

Question 28

Object recognition requires memory. What does this mean about the connectivity of IT?

Answer 28

Object recongnition requires that we have seen that thing before and have memory of that thing. Therefore, IT is connected to other areas of the brain that are involved in memory.

Question 29

Object recognition does not just involve recognising visual objects. It also requires....

Answer 29

Combining information from other areas of the experience, such as touch, memories, associations, emotions. This means that IT must be highly interconnected with other areas of the brain, which all come together and aid in object recognition.

Question 30

What area of the visual cortex is linked with recognition/processing of curvature and surface shape?

Answer 30

V4

Question 31

What does AGNOSIA mean?

Answer 31

The inability to know.

Question 32

What is PROSOPAGNOSIA?

Answer 32

The inability to recognise faces.

Question 33

What is the inversion effect and what does it tell us about the neurons responsible for facial recognition?

Answer 33

The inversion effect refers to the phenomenon that when a face is inverted and distorted we do not recognise the distortion to the same degree that we would should that face be upright. This inversion effect does not apply to other objects in the way it does to faces. This suggests that the neurons responsible for facial recognition are most receptive to visual information about faces when they are the right way up. This makes a lot of intuitive sense.

Question 34

Is there evidence that other primates have neurons/cortical areas that respond to faces?

Answer 34

Yes. There has been compelling evidence generated about a similar area as the FFA in primates that is activated when presented with a face. This area does not activate when the visual data is scrambled or not complete, suggesting that is area is specifically activated in response to faces.

Question 35

Taso et al (2006) collected very compelling evidence that primates have a specific area for facial recognition. What brain imaging did they use?

Answer 35

fMRI

Question 36

Who coined the region Fusiform Face Area?

Answer 36

Nancy Kanwisher

Question 37

The inversion effect is seen for facial recognition. What other visual stimuli has an inversion effect?

Answer 37

Natural scenes.

Question 38

What does the current research indicate about the brain regions for object recognition and scene recognition?

Answer 38

It appears that the regions responsible for object recognition and scene recognition are distinct. Damage to the object recognition area leading to object agnosia does not mean that there will be scene agnosia as well. The area responsible for scene recognition is the Parahippocampal Place Area (PPA).