Lecture 27 - Higher Visual Functions: Object recognition (AMcK)

Question 1

What techniques have been used to determine how the brain enables us to perceive objects?

Answer 1

fMRI, lesion studies, animal studies, single cell neurophysiology

Question 2

What info is fed-forward from V1?

Answer 2

-Discrete orientation info -colour -Linked borders/contours -Some boundary and edge info *Starting point (retinotopic organisation and orientation selectivity)

Question 3

There are long-range interactions between neurons Previously you could not see the patch in the middle by itself. Put two patches next to it and suddenly you will be able to see the one in the middle. This is because there are cells that are encoding similar features that are connected by horizontal connections that amplify the signal

Answer 3

There are long-range interactions between neurons Previously you could not see the patch in the middle by itself. Put two patches next to it and suddenly you will be able to see the one in the middle. This is because there are cells that are encoding similar features that are connected by horizontal connections that amplify the signal

Question 4

x% of orientation difference is required for elements to be viewed as a contour

Answer 4

30 or less than

Question 5

What info does V2 process?

Answer 5

Orientation, colour, continue processing of contours (illusionary contours - we see these contours as often objects are partially occluded in natural scenes yet the visual system enables seamless completion of these objects)

Question 6

T/F - V1 cells can also respond to illusory contours like V2 cells

Answer 6

F- V1 cannot

Question 7

What info does V4 process?

Answer 7

Integration of local cues into global shape percepts

Question 8

What are two types of stimuli used to study global integration of form cue?

Answer 8

1) Glass patterns Allow us to control orientation information and different amounts of coherence
2) Global shapes not from texture

Question 9

fMRI study is looking at what sort of stimuli can activate certain cortical areas. When shown a concentric, radial or parallel thing - how did: a) V1 respond b) V4 respond c) FFA respond

Answer 9

a) V1 responded equally to all
b) V4 responded more to concentric and radial patterns as these stimuli encode an object structure c) FFA responded to concentric as the face is quite round

Question 10

What is the role of the lateral occipital cortex? Inferior occipital cortex?

Answer 10

Global shape processing Texture analysis

Question 11

Aperceptive agnosia

Answer 11

Can’t integrate the component visual features into a global whole (but low-level colour, motion, orientation perception is intact) E.g. if asked to draw a copy of an object, might draw major features but not connectivity

Question 12

Associative agnosia

Answer 12

Can’t identify the object with the required knowledge of it. May be able to copy it but don’t recognise what it is

Question 13

Prosopagnosia is? Due to damage to?

Answer 13

Face blindness, Damage to FFA