4 - Representation of motion in dorsal pathway Flashcards
What is a delay-and-compare model?
A model that compares what happens in one region of the retina with what happened shortly before in a nearby area, using some form of time delay mechanism.
How does adding a spatial frequency filter to the delay-and-compare model help us?
The filter will only fire if it sees a specific pattern, so won’t just fire for a difference in luminance.
What is an edge-based model
A model that analyzes the change in illumination over time in conjunction with an edge detector to determine movement.
What is a spatial-frequency-based model?
A model of which the motion filters can be turned to different rates of motion by responding to different orientations of lines in space-time. There is a filter responding to slow upward motion and another filter responding to fast upward motion.
What is the aperture problem?
Estimates of local motion along the edges of an object may not provide the best interpretation of the object’s motion as a whole.
What is the aperture problem?
Estimates of local motion along the edges of an object may not provide the best interpretation of the object’s motion as a whole.
What do component cells respond to?
Respond to the components of a potential coherent percept
What do pattern cells respond to?
Respond to coherent percept
Why is it logical that similar contrasts and similar spatial frequency get grouped together?
Because you only group things together that belong together to the same object. Often things that belong to the same object look similar.
What is the function of a pattern cell?
Determines which local estimates provide the best information about the movement of the object as a whole, putting particular weight on unique points.
What is the method of Adelson?
Shown two gratings moving in different directions. varied contrast and spatial frequency. Asked participants if they view it as coherent or not
What is the solution that Adelson comes up with?
The velocity space combination rule. The constraint lines of the gratings converge at a point- that point is the endpoint of perceived motion
How can you test whether motion perception happens in one stage or in two stages?
if one stage - unidimensional noise orthogonal to the motion of plaid would maximally distort a coherent percept (not observed, pattern cell does not represent blob-motion so one stage is unlikely)
If two stage - unidimensional noise orthogonal to the components of the plaid would maximally distort a coherent percept. (observed, orientation-selective process (component neurons) must precede the analysis of coherent motion (pattern neurons)
