Visual System IV Flashcards
What is each stream (dorsal/ventral) mostly involved in, and whats their main input (magnocellular/parvocellular)
Dorsal stream: visual input thats required for action (for you to move). The magnocellular input
Ventral stream: more involved in perception, analysis of form, colour, faces. Parvocellular input
As we move to higher cortical areas, neuronal receptive fields tend to get ______ (smaller/larger) but required stimuli get more specific.
LARGER
theyre more interested in specializing certain components of visual input, they wont care as much about receptive fields so these get bigger
Dorsal stream:
- __________ input
- towards ___________ cortex
- ________ pathway
Ventral stream
- __________ input
- towards ___________ cortex
- ________ pathway
Dorsal:
- MAGNO input
- towards parietal cortex
- action pathway
Ventral:
- PARVO input
- towards inferotemporal cortex
- perception pathway
What are the two processing pathways that extrastriate visual areas form?
- a ventral pathway (PERCEPTION) concerns with object recognition, with neurons selective to shape, colour, and texture
- a dorsal pathway (ACTION) concerns with the spatial relationships of objects, with neurons that are selective to the speed and direction of movement as well as visual disparity (depth)
What are some other names for primary visual cortex
area 17, striate cortex, V1
What is the direction of visual motion.
area MT, V1, MST
area V1 –> area MT –> area MST
T or F: neurons are tuned for the direction of visual motion.
True. Line segment has to move through the receptive field in a particular orientation. The directions of motion of the line are changing the activity of the cell.
Which cortexs have columnar organization of neurons?
V1, MT, mst?
What is the difference?
all!
Just as the orientation/ocular dominance columns were present in V1, columns containing neurons that respond to directions of motion exist in area MT.
Summary:
- V1: line segments
- MT: tuned for direction of motion (motion processing)
- MST: optic flow
What is the receptive field size difference in MST vs V1 vs MT?
V1 < MT < MST
MST: visual receptive fields even bigger, sometimes half of the visual field
review the monkey coherence line arrow expriemtn in visual system IV slides. what is the summary?
Perception (visual) was shifted by microstimulation
Why does the visual field move on your retina?
Because you are moving.
When the visual field is moving on your retina, that’s because YOU are moving
Whatare the 8 different kinds of stimuli
8 diff kinds of stimuli in MST
4 planar to left/right down/up, two circular (CW or CCW), two radial (expanding/contracting)
What happens in the retina when a person is moving?
When a person moves, the entire visual field shifts across the retina, creating patterns of optic flow. These patterns depend on the direction of movement—expansion when moving forward, contraction when moving backward, and rotational or planar motion for turning or lateral movements.
How do neurons in the MST area contribute to self-motion perception?
Neurons in the MST area respond preferentially to optic flow, which is the pattern of motion on the retina that occurs when a person moves. By analyzing optic flow, MST helps determine heading direction and distinguish between self-motion and object motion in the environment.
What is retinal disparity?
the difference in location of image between the two eyes. The disparity signal is derived in extrastriate cortex (dorsal stream). this signal is critical for depth perception.
crossed disparity: points closer than fixation point
uncrossed disparity: points farther away from fixation point
Basically:
Stuff going on in depth, and two eyes laterally disaplced
Whatever you focus on you put the fovea on (eg the tree), but the thumb is going on to the righ part of one fovea and the left part of the other. Which causes you to see two thumbs
This is retinal disparity
T or F: Cortical area MST and other dorsal stream areas have disparity tuning.
TRUE
How does disparity tuning in MST and other dorsal stream areas contribute to visual processing?
Disparity tuning allows neurons in MST and other dorsal stream areas to detect differences between the images from each eye, helping to perceive depth and three-dimensional structure. This is essential for accurately interpreting optic flow, estimating distances, and guiding movement through space.
