M2 Lecture 12: Feb 21 Flashcards
what is Apparent motion:
The illusory impression of smooth motion resulting from the rapid alternation of objects that appear in different locations in rapid succession.
explain Motion detection circuit
- M neuron registers a change in position between A and B.
- Add neuron D which incorporates delay
- Repeat this across many X comparator neurons
explain the the What pathway has what kind of cells
P ganglion cells receive inputs from midget bipolar cells (1 cone per midget cell). P cells project to the parvocellular layers of the LGN.
P ganglion cells have small receptive fields. The high-resolution information coming from these P cells is at the origings of the ventral «what» pathway
explain the where pathway
M ganglion cells receive inputs from diffuse bipolar cells (>1 cone per diffuse cell). M cells project to the magnocellular layers of the LGN.
M ganglion cells have large receptive fields and are sensitive to movement
what is the Correspondance problem:
The problem faced by the motion detection system of knowing which feature in frame 2 corresponds to which feature in frame 1.
what is the Aperture problem:
The fact that when a moving object is viewed through an aperture (or a receptive field), the direction of motion of a local feature or part of an object may be ambiguous.
what are apertures
receptive fields
Motion information from several local apertures (or receptive fields) can be combined to determine what
the global motion of the object.
There are several directions of motion within each aperture that are compatible with the stimulation the receptor is receiving
how to determine the true global motion direction of the object.
Whichever possible motion direction is the same in all apertures is the true global motion direction of the object.
Lesions in magnocellular layers of LGN impair what
perception of large, rapidly moving objects
Monkeys needed____ times as many dots to correctly identify direction of motion
about ten
what also plays an important role in motion perception
Middle temporal area (MT)
what is Motion aftereffect (MAE):
The illusion of motion of a stationary object that occurs after prolonged exposure to a moving object
Existence of MAE implies what
an opponent process system, like that of color vision
what is Interocular transfer:
The transfer of an effect (such as adaptation) from one eye to another
explain Interocular transfer and how it relates to MAE
MAE exhibits interocular transfer.
- > Therefore, MAE must occur in neurons that respond to both eyes. - > Input from both eyes is combined in area V1, so MAE must be in V1 or later. - > Recent studies with fMRI confirm that adaptation in MT is responsible for MAE.
whats First-order motion:
The motion of an object that is defined by changes in luminance
what is Luminance-defined object:
An object that is delineated by differences in reflected light.
what is Second-order motion:
The motion of an object that is defined by changes in contrast or texture, but not by luminance
what is Texture-defined (contrast-defined) object: (second order motion)
An object that is defined by changes in contrast or texture, but not by luminance.
Indicates that the visual system does not simply track objects’ positions over time to calculate movement, as this display demonstrates (since there are no objects to track!).
is seeing passive
no
Why do we perceive the finger to be in motion in the first case, but perceive the fixation point to be stationary in the second case? After all, both items moved across our retinas to the left.
-> Because in the second case there was an eye movement
what are the Types of eye movements
smooth pursuit saccade vergence Reflexive eye movements: Microsaccade
what is Smooth pursuit:
Voluntary eye movement in which the eyes move smoothly to follow a moving object.
what is Saccade:
A type of eye movement, made both voluntarily and involuntarily, in which the eyes rapidly change fixation from one object or location to another (3-4 seconds every second).
