V1 and Beyond! Flashcards
What is V1?
V1 refers to the primary visual cortex
Can simple cells help us detect the orientation of lines?
Although simple cells react to some lines with a given orientation, we can’t detect the orientation through the information of a simple cell.
To detect orientation, we have to get the information from several retinal ganglion cells.
Describe the plot.
Here you have two cells: cell A in red and cell B in blue and we are measuring their response to different angles of lines.
Notice that cell A responds better to 90 degrees lines whereas cell B responds better to lines inclined 60 degrees.
You can also notice that the two curves overlap having a certain degree of the orientation of a line where they respond with the same intensity.
Tire-after-effect
What is it?
This is when we spend a long time staring to a pattern and our eyed “adapt”.
In other words, after a while looking at a pattern of stripes will “tire” the group of neurons specialised in that orientation and so this will shift the balance to the opposite direction.
What is a hypercolumn?
1 mm of striate cortex.
Each hypercolumn contains cells responding to every possible orientation (0 to 180 degrees), with one set preferring the input from the right side and another with preferring the input of the left side.
What is retinotopy?
It is the visual information coming from adjacent locations in the retina that will afterwards project in the primary visual cortex.
What is the extrastriate cortex?
The extrastriate cortex is composed of the brain regions bordering the primary visual cortex that contains other areas involved in visual processing.
What happens after the extrastriate cortex?
We get two pathways:
Dorsal pathway
Ventral pathway
What is the function of the dorsal pathway?
The dorsal pathway is concerned with the locations and shapes of objects but not the names or functions.
It is the “where” pathway.
what is the function of the ventral pathway?
The ventral pathway is concerned with the names and the functions of objects regardless of the location.
It is the “what” pathway.
Extrastriate Cortex
Brain regions bordering V1 containing other areas involved in visual processing.
(V2,V3,V4,etc.)
True or False
Early areas after V1 (V2, V3, V4, etc.), maintain a retinotopic organization.
True
True or False
The size of the receptive field decreases and the complexity increases as you go from V1 to higher levels areas.
False.
The size of the receptive field increases and the complexity increases as you go from V1 to higher levels areas.
How will the cells in V1 react to each image?
How will the cells in V2 react to each image?
V1 will react in the same way for both images. V2 will react more to (a) since the square has the dark edge.
To which types of edges V4 neurons react to?
Concave, convex and straight edges.
