5 - Representation of objects in the ventral stream

Question 1

Give evidence for the statement that there are no specialized areas for object vision

Answer 1

• Each category shows a distinct pattern and even if we exclude a maximally responding voxel that could be seen as a specialized area, the correlations within-category remained high why the between-category correlations remained low. Therefore showing that category could be determined based on the pattern of neural responses.
• Humans and monkeys share similar patterns in the inferior temporal lobe for object recognition. There are interspecies consistencies. When comparing the human early visual cortex and human inferior temporal lobe there is a big difference between within and between animate and inanimate objects. This indicates a boundary for category.
• Subareas of the lateral occipital complex are related to the physical shape similarities (posterior LOC - LO) and to the subjective perceptual shape similarities (anterior LOC - pFs - posterior fusiform sulcus). Activation patterns in subregions of object-selelctive cortex encode objects according to a hierarchy.

Question 2

Give evidence for the statement that there are specialized areas

Answer 2

• Different objects have specificic eccentiricity bisases. Objects that have to be identified by looking at fine details need to be located in a visual area where central vision is located.
• There are weak selectivity maps that exist for many functional properties. When they are studied in isolation, weak selectivity is found. But when a stimulus combines several functional properties, multiple maps are activated and eventual selectivity is a combination of these multiple maps.

Question 3

Give evidence for the statement that experience is needed for the formation of the representations in the ventral route

Answer 3

The response correlations of nearby neruons varied according to experience. They tended to develop similar stimulus preferences follwoing at least 1 day of experience with those stimuli. This was not the case when presented to novel stimuli.

Question 4

What is the method of Haxby?

Answer 4

fMRI while viewing faces, cats, objects and control nonsense images.
aim - determine whether each stimulus category evoked a pattern of response in ventral object vision pathway that could be distinguished from patterns evoked by all other individual categories correlations between patterns

Question 5

What is the method of Kriegeskorte?

Answer 5

Monkey single cell recording and correlating with human fMRI for animate and inanimate objects. evaluated with a representational dissimilarity matrix

Question 6

What is a representational dissimilarity matrix?

Answer 6

Shows which distinction between stimuli are emphasized and which are deemphasized in the representation, thus encapsulating the information content of the representation.

Question 7

What is the method of Haushofer

Answer 7

fMRI showing novel shapes, made matrix of physical similarity and perceptual similarity and compared it to the activity in the anterior and posterior LOC

Question 8

What is the method of Malach?

Answer 8

fMRI, eccentricity experiment with a thick ring filled with objects

Question 9

What is the method of Erikson?

Answer 9

Measure electrophysiology both single unit and multiunit and see if familiar and novel stimuli cause different activity in a pair of near neurons or a pair of distant neurons.

Question 10

What is the method of Mahon

Answer 10

fMRI showed living and nonliving stimuli and seeing if the same lateral-to-medial organization pops up in congenitally bling individuals. task - size judgement either auditory or visual