ND - Motion Perception - Week 1 Flashcards
Distinguish between simple and apparent motion using examples of each.
Simple - a ball being thrown
Apparent - a sequence of lights in a neon sign
List three natural reasons why motion perception is important.
Navigation
Hazard avoidance
Segmentation of objects
Define optic flow.
Movement of the world
Describe the motion pathway in the brain. Describe where both parvocellular and magnocellular signalling goes to.
Parvocellular - Retina - LGN - V1 - V4 - Ventral temporal pathway
Magnocellular - Retina - LGN - V1 - MT - Dorsal parietal pathway
Which cells are responsible for parvocellular and magnocellular signalling?
Parvocellular - midget ganglion cells
Magnocellular - parasol ganglion cells
Do V1 cells show direction selectivity?
Yesd
What does the directional selectivity of a neuron depend on? Briefly describe what this means using a set of 5 neurons labelled a-e.
The response latency of the presynaptic neurons
Consider a series of neurons, a-e. Consider them to be directionally sensitive to left-right movement.
They are connected to the target cell such that they will fire sequentially from a-e, if a leftward movement occurs, and this is because their signals arrive simultaneously and sum, reaching threshold.
If a rightward movement occurs, then d/e will fire first, followed by c, b, and a. This results in insufficient summation and threshold is not reached.
Are directionally selective cells distributed evenly throughout V1?
No, the proportion of cells that are direction-selective varies according to V1 layers
Where does MST lie in humans?
Adjacent to MT (also known as V5)
Do M- and P-systems follow completely separate pathways or is there crosstalk?
Not completely separate, there is crosstalk between dorsal and ventral streams
Define akinetopsia.
Visual motion blindness
Is the M-system the only motion pathway in the human system?
No, there is also the colliculo-cortical pathway
Retina - superior colliculus - V5
What do the following areas of the brain process?
V1
V5/MT
MST
V1 - direction selectivity
V5/MT - global motion integration
MST - optic flow
