Chapter 8 - Lecture Section 8.2 Flashcards
Elementary Motion Detectors that occur in the Retina can code for ___.
motion
There’s further processing of motion in the ___.
Cortex
One piece of evidence that emphasizes the importance of cortical motion processing is using ___.
Developmental Studies (use it or lose it)
Motion coding in Cortex affects ___.
perception
Kittens who are raised in a stroboscopic environment, meaning illumination is provided by a strobe light, and the light isn’t on for long enough for any motion to be perceived, eliminates direction-selectivity in the ___, so there are no neurons that can be recorded in the primary visual cortex that respond to particular direction, and the ability to determine the direction of a moving stimulus. When these cats are tested behaviourally, they lose the ability to determine the direction of a ___, they become ___.
striate cortex // moving stimulus // motion-blind
Even when Elementary Motion Detectors in the Retina are working, there also must be motion coding in the ___ in order to produce the percept of motion.
Cortex
Electrophysiological investigation of the visual system has discovered Direction selective neurons in various regions that ___ most when motion in their receptive fields goes in a specific direction, and often they are inhibited when motion goes in the ___ direction.
spike // opposite
There is an area in the Dorsal Stream that receives input from the Primary Visual Cortex called the ___.
Middle Temporal cortex (MT)
The Middle Temporal cortex (MT) projects to the ___.
Medial Superior Temporal Cortex (MST)
Throughout the Motion-Coding pathway, the Receptive Fields get ___, and Motion-Coding gets more ___.
larger // complex
How can ambiguity about how stimulus direction is coded be reduced?
By Population (distributed) Coding
In the Aperture Problem, most people report that they see the bars moving ___ to ___.
L // R
In the Aperture Problem, the direction of the bars perceived in the Receptive Field ___ represent the actual direction of the stimulus’s movement.
doesn’t
A neuron’s ___ acts the same way as the Aperture
Receptive Field
In the Aperture Problem, when you cannot see the edges or corners of these bars and just a single orientation feature, the perceived motion is ___ to the orientation of the feature. In other words, these bars are vertical, and when they are moved in all sorts of direction, you perceive motion as only going straight L to R because you cannot see the corners.
perpendicular
In the Aperture Problem, all movement of a bar/grating is seen as ___ to the long contour.
perpendicular
The Aperture Problem: If a person is walking upstairs L to R, and the flagpole is the only thing that’s visible in the Receptive Field, we will confuse what the Receptive Field is telling us from what the stimulus is actually doing, we will only see the person as moving ___ and not ___.
L to R // upstairs
The main problem is that The Aperture problem creates an ambiguous ___, and the question becomes, how does the visual system solve this ambiguous ___?
motion signal // motion signal
When we have a plaid grating, most people will see the pattern drifting from ___. When the reality is that one grating drifts ___ and to the ___ and the other grating drifts ___ to the R. Within the receptive field that information is combined together and the upward component and downward component ___ each other out, such that you only see the ___ component.
L to R // up // R // down // R // cancel // rightward
A single Grating (not a plaid) is referred to as a ___.
Component
If you put the two Component Gratings together, creating a Plaid, their downward and upward motions ___ each other out and you just get motion to the ___, so this is ____, and this would be the motion of the Components.
cancel // right // coherent pattern motion
If you put the two Component Gratings together, their downward and upward motions ___ each other out and you just get motion to the ___, so this is ____, and this would be the motion of the components.
cancel // right // coherent pattern motion
Complex Cells in V1 as well as some in the MT only respond to the ___.
Component motion
Complex Component Cells/Neurons in V1 as well as some in the MT only respond in a way to the Gratings and Plaids that ___ match perception, it responds “good” to only the ___.
does not // Component motion
Imagine we’re recording from a ‘Component’ cell that prefers L to R motion. If we have a square Plaid, the Plaid that we perceive as moving as up and to the R, it’s got a Component within it that’s moving straight R, and so this is gonna give it a ___ response.
good
Imagine we’re recording from a ‘Component’ cell that prefers L to R motion. If we have a Diamond Plaid that’s moving up and to the R, at a 2 o’clock angle, it’s gonna give a ___ response, that’s ___ from its preferred direction, it ___ like it.
poor // too far away // doesn’t
In area MT, there are some cells that respond (about 1/3) to the overall ___ of coherent motion, in other words, their responses ___ the way we perceive gratings and plaids moving.
pattern // match
For around the first ___ of their responses, some MT Pattern cells responded like V1 cells, but afterwards, a preference for the ___ developed.
70ms // Coherent motion
The calculation in MT is taking primary visual cortex input, and it is ___ it together, that calculation takes about ___ to perform, and once it is performed, and the Component signals are combined into a Coherent motion pattern direction, it ___ what we perceive.
summing // 70ms // matches
Who initiated Random Dot Kinetograms?
William Newsome et al
What is the task of Random Dot Kinetograms?
The task is to indicate which direction you perceive the dots as moving.
In Random Dot Kinetograms, the ___, or the ___ that are moving in any particular direction, are changed in order to modulate the difficulty of the task.
Coherence // % of dots
