Chapter 8: Movement and Action Flashcards
Motion:
a change in position over time
Real motion:
motion in the world created by continual change in the position of an object relative to some frame of reference
Apparent motion:
the appearance of real motion
from a sequence of still
images
Correspondence problem (motion perception):
how the visual system knows if an object seen at Time 1 is the same object at Time 2
smooth pursuit
tracking
Induced motion:
an illusion whereby one moving object may cause another object to look as if it is moving
Neurally we look for…
speed, how fast something is moving
direction of movement
proximity
Akinetopsia
– uh·ki·nuh·towp·see·uh
unable to see motion
Motion perception may have
evolved to help our ancestors
perceive…
incoming predators and hunt prey
We need to perceive __________ and ___________ of motion
direction; speed
Motion of small things and ___________ of motion across
space
patterns
Give an example of when motion is either so slow or so fast that it cannot be perceived.
slow: plant bending its leaves toward the direction toward the direction of sunlight which is extremely slow to the human eyes that it can’t be perceived
fast: bicycle wheel that is moving so fast that we can no longer track the individual spokes
What factors influence our motion threshold?
Color, distance, size, etc
Motion thresholds are a function of what parts of the __________ are seeing the motion
retinae
_______________ vision is better for motion detection.
Peripheral
The _________________ (two words) have rather poor motion thresholds. However, the _____________ has
better motion thresholds.
foveal regions; periphery
Apparent motion
is an illusion, example is those flipping books
How slow:
To detect movement, an object must move at least ____________ of 1 degree across the retina
1 minute
Absolute threshold for detection:
– Function of the _________ of the
moving object and it’s ____________ away from the eye
speed; distance
When something is moving too fast, it just looks like a ______.
blur
For a fast thresholds it is dependent on __________.
context
Brightness, size, amount of time visible
Real Motion
Motion created by continual
change in the position of an object
relative to the frame of reference
salient is…
attention grabbing
Apparent Motion
Appearance of real motion from a sequence of still images
Stimuli separated by time and location are actually perceived as a single stimulus moving from one location to another
Induced motion
One moving object may cause another object to look like it’s moving
- moving clouds at night make it look like the moon is moving in the opposite direction
Apparent motion relies on _____________.
correspondence
Regarding correspondence, the visual system must:
- Must assume the objects moving
are the same object - Must determine which parts of
successive images reflect a single
object in motion
Perception of apparent motion controlled in early stage of visual processing
Visual “short cuts”
Salient features
– Most noticeable or important
* Brightness/darkness
* Motion
* texture
to detect correspondence…
Trick of the visual system
– Extract salient features from
complex display
– Search for just those features
Being able to quickly
detect motion and
determine what moved is crucial to __________.
survival
What did the Larsen (2006) study find about apparent motion vs actual motion?
The study found used an fMRI to find out whether apparent motion and actual motion stimulate the same areas, in which resulted that both motions stimulate the same parts of the primary cortex. This meaning that those areas acknowledge apparent motion as if it were real motion.
Some __________ cells in the retina sensitive to motion as it brings signals from rods to the ganglion cells
amacrine
The ________________ (two words) are the beginnings of the M pathway which codes for motion.
optic nerve
___________ and ____________ are coded for at the neural level.
direction; speed
Reichardt Detectors
– Neural circuits that enable the determination of direction and speed of motion
– Tracks delay from one neuron to another
* Delay specifies the speed
* Can also detect direction
Motion-sensitive neurons that get information from different retinal cells (different receptive fields)
Different neurons tuned to different aspects
Each neuron makes a response based on the delay of information between the two input neurons
– Some respond if there is a long delay, some if there is short
– Some respond if it goes one way (from field A to B), some respond if it goes the other way (from field B to A)
Where are the neurons for reichardt detectors?
most likely V1 for humans
non primates also in LGN
Corollary discharge theory
when the object is tracked the superior colliculus must receive a command signal to activate for smooth pursuit where muscles that control eye movements are activated.
corollary: correlation, as something happens something else happens. both the eyes and motor cortex are signaled at the same time
Define Reichardt detectors:
neural circuits that enable the determination of direction and
speed of motion by delaying
input from one receptive field,
to determine speed, to match
the input of another receptive
field, to determine direction
Define corollary discharge theory
the theory that the feedback we get from our eye muscles as our eyes track an object is important to the perception of motion
Reichardt detectors work well when the eyes are ______________, but not so well when the viewer moves their eyes to track motion across a scene
stationary
The _________________________ (three words) is an important concept in understanding how our visual systems detects and tracks motion
corollary discharge theory
The corollary discharge theory states that the motor information sent to the eye is also useful for the brain that processes motion information. T/F
true
Motion aftereffect:
a motion-based visual illusion in which a stationary object is seen as moving in the opposite direction of real or apparent motion just observed
Akinetopsia (motion
blindness):
a rare condition in which an individual is unable to detect motion despite intact visual perception of stationary stimuli, caused by damage to area MT
Point-light walker display:
an experiment in which small lights are attached to the body of a person or an animal, which is then filmed moving in an otherwise completely dark environment
Affordance:
information in the visual world that specifies how that information can be used
ex: Coffee cup- we see the ability to
hold + ability to put liquid in it. Hiking and see a flat tree stump? It “affords” sitting. Don’t see it as a tree, see it as a chair
perceived action possibilities
Gradient of flow:
the difference in the perception of the speeds of objects moving past us in an optic flow display
Focus of expansion:
the destination point in an optic flow display, from which point perceived motion derives
Lateral intraparietal (LIP) area:
an area of the primate parietal cortex involved in the control of eye movements
guides eye movements based on attention to space
Medial intraparietal (MIP) area:
an area of the posterior parietal lobe involved in the planning and control of reaching movements of the arms
for planning and controlling reaching, it is for goal directed movements, and it goes towards visually selected location
Anterior intraparietal (AIP) area:
a region of the posterior parietal lobe involved in the act of grasping
saccade
movement of eye
fixation
eye stops on object
micro-saccade
a tiny saccade that occur even when trying to fixate
Micro-saccades make it that the visual information changes or have slight shifts to prevent visual fading. What detects these changes are the neurons as they are “change detectors.” As these micro changes are occuring neurons keep on firing even when looking at the same thing for a while.
Visual fading occurs when when something stays the same (visual information stays the same) which results in the neurons to stop firing.
(class exercise: trying to fixate on pupil of other person)
Where in the brain is motion processed?
the movement area is MT or V5
___________ is an area of the
occipital cortex critical to motion
perception
MT (aka V5)
medial temporal: it is adjacent to the medial temporal lobe and is within the extrastriatal areas of the occipital lobe
MT receives input from…
V1, V2, and the superior colliculus
MT is sensitive to both __________ and __________ of motion, but not other perceptual characteristics such as color and orientation
direction; speed
What kind of motion is the MT sensitive to?
large scale motion
What did Wigelt (2013) find out?
He studied the movement area of the brain, the MT, in humans using fMRI, where he found out that the MT responds to more to to moving than stationary stimuli, and its attention to motion particularly is important.
When ____ is damaged, a condition known as akinetopsia may occur, in which a patient is unable to detect motion despite intact visual perception of stationary stimuli
MT
Patients with this disorder have perception that resembles a series of still photographs moving one to the next in a type of motion blindness
When MT is damaged, a condition known as ____________ may occur, in which a patient is
unable to detect motion despite intact visual perception of
stationary stimuli
akinetopsia
Patients with this disorder have perception that resembles a series of still photographs moving one to the next in a type of motion blindness
akinetopsia
Your _______________ is a “change detection system”
sensory system
If getting the same sensory info
for awhile, your system will adapt. Give an example of this.
For example, wearing itchy socks, eventually you’ll not feel the itch anymore
For motion aftereffects of visual adaptation what happens?
Seeing movement up for a bit? Your
“up movement” cells will eventually
stop firing as much – no change is
being detected.
* Then, your brain performs a
“competitive comparison” between Up detectors and Down Detectors
* Now that “up” is firing less than base rate, “down” which is still firing at base rate, seems like the “winner” and you’ll see faint “down” movement
– Only lasts until “up” starts firing at
regular rate again- (fairly quickly)
Low level experiments find adaptation in ____ or ___
High level experiments find adaptation in ____
LGN; V1 ; MT
What is an example of a motion aftereffect?
watching a stream rush past for several minutes and then looking at a blank wall and seeing movement in the opposite direction
The area of the posterior parietal lobe involved in the act of grasping is called the anterior intraparietal. T/F
True
When Loretta watches a horse gallop past, she sees the animal as a series of still images. Loretta most likely has a condition called ______.
akineotopsia
During the night, Christopher sees a person walking 50 yards ahead. Even though he cannot see the person’s face or clothes, Christopher knows this person is his friend George by the way he moves. This phenomenon has been proven by the ______.
point-light walker display
The appearance of real motion from still images presented sequentially is called ______.
beta motion
A sky with dark clouds would have an affordance of ______.
precipitation
A person with akinetopsia will have the most difficulty with ______.
catching a baseball
When Martina sees U.S. Air Force planes flying in V-formation across the sky, she consistently sees the pattern of planes even though she cannot track each individual plane. This example illustrates ______.
the correspondence problem
Lars watches geese fly across the sky. This is an example of ______.
real motion
In ______________, you perceive motion but can see that the elements, like the individual bulbs in the Las Vegas displays, do not move.
phi motion
What are the features of motion our visual system must be able to perceive?
Our visual system must be able to perceive salient features, which are the most noticeable or important features. These features can be detected by their brightness/darkness, texture, or motion.
What could you do to make an illusion of “apparent motion” for a friend or roommate?
I could draw a series of still images on sheets of paper, where each of them have the same object at a different location, and by flipping them, the object will seem to be moving.
What is the correspondence problem? (motion perception)
The correspondence problem referring to motion perception, is how we recognize that an object at one position and at a specific time, is the same object at a different position and at a different time.
A way this is done is by our eyes tracking the motion, related to this is the wagon-wheel effect, where we perceive the direction of motion in the opposite direction of the actual motion.
Summarize the Newsome and Pare (1988) study. What were the main results?
The study used single-cell recording on monkeys to find out what stimulates the MT. The results were that when motion was going at the same direction it led to neurons firing much more than when the motion was partially going in the same direction. Motion in this study was created by the movement of dots. This meaning that the MT is sensitive to a large scale motion.
Summarize the main results of Kaas et al. (2010) study about visual imagery.
fMRI’s showed that MT is activated when people imagine perceived motion
Weigelt and her group have also found evidence that MT is active during visual imagery that involves motion
MT is important for higher order aspects of motion perception.
That is, even when there is no actual movement present, but participants are imagining
moving objects, MT is active.
In the study, participants were asked to imagine objects moving without actually seeing the motion of those objects. They compared this with a visual imagery condition that did not involve motion as well as an auditory imagery task. Relative to the control conditions, when participants were engaged in motion visual imagery, larger responses were recorded from MT.
What do researchers use point-light walker displays to investigate?
It is used to investigate how motion can lead to higher level thinking, and how we can make judgments as movement is present. For example, a still image of dots won’t give us much detail or our thoughts may be ambiguous about it. But when motion is displayed we can figure out some things about a person, that include of their gender, height, nervousness, happiness, etc.
How do we perceive motion in optic flow patterns and how do they influence our action in motion?
To see an optic flow pattern of driving along a road or landing a plane.
As we move in one direction, objects appear to get bigger as they approach us. In addition to this being a cue for depth, it also indicates motion. A driver can judge her speed by the rate at which objects are flowing toward her.
_______________ (two words) provides information about distance and consequently can be used to aid in our own movement.
Optic flow
_____________________ (two words) are a function of what parts of the retinae are seeing the motion.
Interestingly, we have rather _______ motion thresholds in the foveal regions of our ret-
inae. But our motion thresholds are much _________ (i.e., better) than our acuity in the periphery of our retinae.
Motion thresholds
poor; lower
An example of corollary discharge theory
When an object is tracked, such as a Frisbee flying across the yard, a command signal must be sent from superior colliculus to the muscles that control eye movements
what is saccadic suppression?
inhibition of retina information
The corrolary discharge theory effectively edits out the blur for us, knowing that’s our own eyes moving. T/F
T
Give a summary of corollary discharge theory
Corollary Discharge helps us understand motion of objects even though our eyes are also moving! MT gets info about eye movements ahead of time and can take them into account when interpreting motion in environment.
Activity in _____________________________ (four words in the temporal lobe is more sensitive to biological
motion than of non-biological motion.
posterior superior temporal sulcus
Probably about inferring the form/object from the motion than about the motion detection itself Point-Light Walker Displays
The goal of perception is to form a representation of the world in our mind. T/F
False, it is to be able to function in our real worlds
Regarding the dorsal pathway, the parietal lobe is
important for integrating…
motor, touch, and visual system
Gets info from MT, V1-V5, superior colliculus, etc
Integrates all this info!
– Interaction allows smooth transition from visual
perception to guided action
