wk1: ND - Object Perception

Question 1

Outline the ventral pathway for transmission of information (4)

Answer 1

V1–> V2 –> V4 –> Infero-temporal cortex

Question 2

Outline the dorsal pathway for transmission of information (4)

Answer 2

V1 –> V2 –> DM/V6 (dorsomedial area) –> posterior parietal cortex

Question 3

In a word or 2, explain the Ventral and Dorsal pathways (2)

Answer 3

Ventral: “What” pathway
Dorsal: “Where” pathway/”How” pathway

Question 4

Which visual pathway stream is involved in object perception? (1)

Answer 4

Ventral stream

Question 5

Can the retina alone distinguish faces?

Answer 5

No. You need your visual system to combine many inputs/responses to do so

Question 6

Before distinguishing objects such as faces, what must the visual system first do? (1)

Answer 6

Interpret global shape

Question 7

What feature of V1 allows objects close together to be perceived more easily? Explain

Answer 7

Long-range interaction between neurons. This means that when you have a target in the centre of 2 other targets, the central target can be more easily seen than it would otherwise thanks to this interaction

Question 8

How does the background relate to an object’s contrast? (1)

Answer 8

Apparent object contrast depends on background: object contrast will appear lower when on a background of higher contrast (this is known as surround suppression) and vice versa

Question 9

How does V1 fare with contours?

Answer 9

V1 has contour integration, which means contours stick out and are more noticeable

Question 10

What is the tilt illusion?

Answer 10

Central circular grating with vertical lines and a larger circular grating around it with diagonal lines. Due to the response of orientation-selective cells to the larger circle, the lines in the inner circle appear tilted rather than vertical

Question 11

What info is fed forward from V1? (3)

Answer 11

Discrete orientation information
Linked borders/contours
Some boundary and edge information

Question 12

Does V1/primary visual cortex tell you what an object is?

Answer 12

No. It only tell you that an object is present

Question 13

What are V2 neurons sensitive to? (3)

Answer 13

V2 neurons are sensitive to orientation, colour, and continue the processing of contours

Question 14

Can V2 respond to illusory contours? What are illusory contours?

Answer 14

yes. Illusory contours are things like fake implied edges such as when you have 2 triangles combined and the edge is implied by pac-man at the vertices

Question 15

What is V4 responsible for?

Answer 15

Integration of local cues into global shape percepts

Question 16

How do we know which parts of the brain are involved in object perception? (2)

Answer 16

Lesions
Functional MRIs

Question 17

In most people, what percentage of coherence is needed to identify a shape?

Answer 17

At least 25%

Question 18

Is texture important to help us recognise overall global form?

Answer 18

yes

Question 19

What type of orientation is V4 more sensitive to?

Answer 19

radial and concentric

Question 20

Define Visual Agnosia

Answer 20

inability to recognise visually presented objects

Question 21

How can visual agnosia occur?

Answer 21

Through damage somewhere along the ventral pathway

Question 22

Define Aperceptive agnosia

Answer 22

can’t integrate the component visual features into a global whole

Question 23

Define Associative agnosia

Answer 23

can’t identify the object with the required knowledge of it (may be able to copy it but doesn’t recognise what it is)

Question 24

Define Prosopagnosia

Answer 24

“face blindness”, ability to recognise faces is impaired, but other object perception and cognition is intact

Question 25

How does Prosopagnosia occur?

Answer 25

Due to damage to the fusiform area (specific part of the human temporal lobe)(