Cortical Processing of Visual Information

Question 1

What is the orienting reflex?

Answer 1

Orientation of the head and eyes to focus salient stimulus on the fovea

Question 2

What is smooth pursuit?

Answer 2

Following of a moving object

Question 3

What is saccadic movement during object inspection?

Answer 3

The movement of the eyes in a way that particular features of the object are projected onto the fovea

Question 4

Ablation of the optic tectum leads to the _____ of the orienting reflex

Answer 4

Disappearance

Question 5

Superior colliculus

Answer 5

Receives input from ganglion cells, auditory system and somatosensory system
Integrates information from different sensory modalities

Question 6

What is the main function of the superior colliculus?

Answer 6

Regulation of saccadic movements

Question 7

What is a retinotopic map?

Answer 7

Organisation whereby neighbouring cells in the retina feed information to neighbouring places in their target structures (LGN, SC, cortex)

Question 8

Foveation hypothesis

Answer 8

States that interaction between retinotopic maps of the visual neurones and topographic maps of the motor neurones initiates orienting reflex

Question 9

Why is foveation hypothesis invalid?

Answer 9

Interaction between the maps seems to be indirect

Question 10

Lateral geniculate nucleus

Answer 10

6 layers
Monocular input
Layers alternate input from one eye
Organised retinotopically

Question 11

Which layers receive information from the contralateral eye?

Answer 11

1, 4 and 6

Question 12

Which layers receive information from the ipsilateral eye?

Answer 12

2, 3 and 5

Question 13

Which layers receive information from M cells?

Answer 13

1 and 2

Question 14

Which layers receive information from P cells?

Answer 14

Layers 3 - 6

Question 15

What is scale invariance?

Answer 15

Being able to recognise an object even when they have been scaled to a size which we haven’t encountered before

Question 16

What is orientation invariance?

Answer 16

Being able to recognise objects even when they are in an orientation which we haven’t previously experienced

Question 17

Hierarchical model of object recognition (simplified model)

Answer 17

Detection of edges

Detection of combination of edges and contours

Detection of object parts (eg. face)

Detection of objects from one point of view (a person from the front)

View-invariant object detection (particular person, a car)

Categorisation (a human, an animal, a vehicle etc)

Question 18

Along the ventral stream, the complexity of responses of neurons _____, as does the size of the receptive field of the neurons

Answer 18

Increases

Question 19

Key features of the cortical structure

Answer 19

Layering 
Columns (ocular dominance, orientation, direction) and blobs

Question 20

Ocular dominance columns experiment

Answer 20

Inject radioactive proline in one eye
Or inject radioactive glucose in the cortex and stimulate one eye
Labelled column receives information from one eye, and unlabelled column from the other

Question 21

Orientation column

Answer 21

Each column, neurons respond to edge in a particular orientation
Each column is a different orientation

Question 22

Blobs

Answer 22

Contain neurones which are specifically tuned to process information about colours

Question 23

What is a hypercolumn?

Answer 23

Three types of columns together

Unit which can process all the useful information for object recognition

Question 24

Hubel and Wiesel

Answer 24

Inserted electrodes into cats brains in different cortical areas (mainly D1)
Made cats look at screen and look at visual stimuli

Question 25

Three types of cells in V1

Answer 25

Simple
Complex
Hypercomplex

Question 26

Complex cells response

Answer 26

Responds to a bar in certain orientation when presented anywhere in the receptive field

Question 27

Simple cells response

Answer 27

Responds to a bar in a certain orientation when presented in the centre of the receptive field

Question 28

Hypercomplex cells response

Answer 28

End-stopped complex cell
Responds to a bar in a certain orientation anywhere in the receptive field
Stops responding when the bar goes out of the receptive field