object recognition Flashcards
State the properties of the Lateral Geniculate nucleus
Has 6 layers Monocular input Layers alternate input from each eye P- and M-Ganglion Cells remain segregated Organized retinotopically
State the organisation in the lateral geniculate nucleus
Retinotopic organisation
What is monocular input?
Receives input from ganglion cells located in one eye only.
What is the lateral geniculate nucleus?
Thalamic ‘relay’ station.
What makes connections with LGN projection neurons?
Ganglion cell axons makes 1:1 connection with it – not much integration happening at this layer
Where does most of the input to the LGN come from?
60% of synaptic input comes from the cortex (back propagation)
Shows Cortex tightly regulates activity of LGN
What is there a lot of in the LGN and what does this show?
Many local interneurons
Lots of processing happening
After the LGN where does the information go to next?
The V1 cortex
State two types of object recognition
Orientation invariance
Scale invariance
Explain orientation variance
One can recognise both objects in any orientation even one that they have never experienced before
What are the steps in Hierarchical model?
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)
What do lesions in inferior temporal cortex lead to?
Decrease in the ability to recognise objects
What increases in the neurons along the ventral stream?
Increase in complexity of responses
Increase in receptive field size of neurons
State the different columnar organisation in the cortex
Ocular dominance column
- Orientation (direction) columns
- Blobs (colour)
Describe the experiments used to find ocular dominance columns in the visual cortex
¥ Inject radioactive proline in one eye
¥ Inject radioactive glucose in the cortex and stimulate one eye with light
What is the function of the blob column?
Processes information about colour
Very good at discriminating between different colours
Where do blob columns receive their inputs from?
Receive input mainly from parvocellular layers of the LGN
What is the hypercolumn?
A structure of the three columns shown together
Ocular dominance columns, orientation columns and blobs.
Describe the Hubel and wiesel experiment
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.
What do simple cells in V1 cortex respond to?
Respond to a bar oriented in certain direction presented in the centre of the receptive field
Where are face sensitive neurons located?
and
What’s the function of face sensitive neuron?
In temporal lobe and Respond to stimuli that resemble faces
What does the Jennifer Aniston model show?
In our brain neurons respond to presentational specific objects
Using the Jennifer Aniston model experiment, what did recordings from human show?
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.
What are the problems with the Jenifer Aniston model?
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.
