object recognition

Question 1

State the properties of the Lateral Geniculate nucleus

Answer 1

Has 6 layers
Monocular input
Layers alternate input from each eye
P- and M-Ganglion Cells 
remain segregated
Organized retinotopically

Question 2

State the organisation in the lateral geniculate nucleus

Answer 2

Retinotopic organisation

Question 3

What is monocular input?

Answer 3

Receives input from ganglion cells located in one eye only.

Question 4

What is the lateral geniculate nucleus?

Answer 4

Thalamic ‘relay’ station.

Question 5

What makes connections with LGN projection neurons?

Answer 5

Ganglion cell axons makes 1:1 connection with it – not much integration happening at this layer

Question 6

Where does most of the input to the LGN come from?

Answer 6

60% of synaptic input comes from the cortex (back propagation)
Shows Cortex tightly regulates activity of LGN

Question 7

What is there a lot of in the LGN and what does this show?

Answer 7

Many local interneurons

Lots of processing happening

Question 8

After the LGN where does the information go to next?

Answer 8

The V1 cortex

Question 9

State two types of object recognition

Answer 9

Orientation invariance

Scale invariance

Question 10

Explain orientation variance

Answer 10

One can recognise both objects in any orientation even one that they have never experienced before

Question 11

What are the steps in Hierarchical model?

Answer 11

Detection of edges
Detection of combination of edges and contours
Detection of object parts (eg face)
Detection of objects from one point of view ( eg a person from front)
View-invariant object detection (particular person, a car)
Categorisation (eg human, an animal, a vehicle)

Question 12

What do lesions in inferior temporal cortex lead to?

Answer 12

Decrease in the ability to recognise objects

Question 13

What increases in the neurons along the ventral stream?

Answer 13

Increase in complexity of responses

Increase in receptive field size of neurons

Question 14

State the different columnar organisation in the cortex

Answer 14

Ocular dominance column

• Orientation (direction) columns
• Blobs (colour)

Question 15

Describe the experiments used to find ocular dominance columns in the visual cortex

Answer 15

¥ Inject radioactive proline in one eye

¥ Inject radioactive glucose in the cortex and stimulate one eye with light

Question 16

What is the function of the blob column?

Answer 16

Processes information about colour

Very good at discriminating between different colours

Question 17

Where do blob columns receive their inputs from?

Answer 17

Receive input mainly from parvocellular layers of the LGN

Question 18

What is the hypercolumn?

Answer 18

A structure of the three columns shown together

Ocular dominance columns, orientation columns and blobs.

Question 19

Describe the Hubel and wiesel experiment

Answer 19

they recorded neurons in different parts of the cat brain (mainly V1) while cat was looking at a screen showing shapes in different orientations, moving in different directions etc.

Question 20

What do simple cells in V1 cortex respond to?

Answer 20

Respond to a bar oriented in certain direction presented in the centre of the receptive field

Question 21

Where are face sensitive neurons located?
and
What’s the function of face sensitive neuron?

Answer 21

In temporal lobe and Respond to stimuli that resemble faces

Question 22

What does the Jennifer Aniston model show?

Answer 22

In our brain neurons respond to presentational specific objects

Question 23

Using the Jennifer Aniston model experiment, what did recordings from human show?

Answer 23

Patients view large number of images quickly.
Some neurons were specifically responding to presentation of either a specific person or specific object. – responding to images of Jennifer Aniston (all different appearances).
Neurons were responding to presentation of these images.

Question 24

What are the problems with the Jenifer Aniston model?

Answer 24

Still poor in scale- and orientation invariance
Do not consider feedbacks from higher cortical areas (“top-down regulation”)
Need experimental validation which is difficult, because one need to record pre- and postsynaptic responses.