Perception Flashcards
Briefly describe the visual pathway.
Eye -> Retina -> LGN -> Primary visual cortex
What are ‘simple’ cells in V1 selective for?
Position on retina, orientation of edge/bar and size/width of bar.
What are ‘complex ‘ cells in V1 selective for (in addition to ‘simple’ cell sensitivity)?
Movement within the receptive field.
What are ‘complex ‘ cells in V1 selective for (in addition to ‘simple’ cell sensitivity)?
The length of the edge or bar - Must stop at one/both ends.
How does V1 detect so many different shapes?
There are many different receptive fields, with different orientation, spatial scales and positions.
What leads to a local virus defect?
Damage to V1.
How is the V1 mapped?
On the cortex, with areas processing contours on particular regions of the retina.
What is the catchphrase for Gestalt psychology?
“The whole is more than the sum of the parts.”
Give the 5 Gestalt ‘grouping principles.’
Similarity, proximity, closure, good continuation and common fate.
Which cells are selective for edges defined by good continuity and closure?
V2 cells
Which ‘grouping principles’ are impaired by V2 damage?
Good continuity, closure and similarity (particularly colour).
Give 6 examples of things which change an object’s image.
Distance, position, perspective view, orientation, lighting and occlusion of parts.
Describe object agnosia.
The failure to recognise without any loss of intelligence or vision.
Describe Marr’s model of recognition.
Edge filters use Gestalt grouping to separate segments and arrange them as cylinders to match 3D memorised models.
Suggest a problem with Marr’s model of recognition.
Many objects are hard to recognise if upside down or rotated.
Describe Biederman’s ‘Recognition by Components.’
Geon types and arrangement for each part of an object are determined and matched to a memorised description.
Describe a problem with Biederman’s ‘Recognition by Components.’
It does not differentiate objects within classes.
What do cells in the temporal cortex code for?
Shape, colour and texture.