Chapter 8 - Lecture Section 8.1 Flashcards
Why is Motion perception is important for survival?
Helps detect prey (e.g. frog hiding) and predators (e.g. leopard stalking)
What information does Motion provide about an object?
- Object shape and segregation
- Attention, is highly salient
- Depth
- Navigation + Proprioception/balance
Motion can be useful for ___ an object from its surroundings.
segregating
Motion separates ___ from ___.
figure // ground
Motion is a highly-salient, attention-grabbing feature, it’s a very good way of inducing ___.
Attentional Capture
What is a break in camouflage?
A break in camouflage is when an animal or person is camouflaged, but when they start moving, you’re able to discern their structure from the surrounding structure.
A break in camouflage is an example of ___.
Attentional Capture
How does Motion help with object recognition?
Motion helps with object recognition (depth/shape/form from motion) either when you are able to move, or the object is moving relative to you and you see all of the different parts of the object, and so you can discern shapes that were only visible from certain viewpoints.
Motion can add a sense of ___ to a ___ image.
shape // flat
What is the Kinetic Depth Affect?
The gif of a field of dots that are moving in a particular way, and because of the speed of motion of each dot is set up in a specific pattern what you typically see is a rotating sphere.
The impression that this is a rotating sphere is called the Kinetic Depth Affect
What is the most powerful depth cue?
Motion Parallax
Motion Parallax requires ___.
Motion
Motion Parallax helps with ___.
Depth perception
Visual motion is also important for the processing of ___, the movement of your body through the environment.
Self-motion (Optic flow)
What Self-Movement skills are needed when driving/flying?
- Navigation
- Steering
- Speed estimation
What Self-Movement skills are needed for body sense??
- Navigation
- Trajectory
- Speed
- Posture
- Balance
What have studies shown about your trajectory through the air?
Studies have shown that your trajectory through the air is more repeatable and accurate if you have your eyes open, so that includes visual signals.
What is Motion Agnosia (Akinetopsia)?
Damage to various modules along the dorsal/Parietal stream can impair the perception of motion, causing the inability to see motion.
Patient L.M. had a stroke to area ~Middle Temporal (MT) cortex, and can no longer perceive ___. Despite the fact that it’s in the Temporal Cortex, we will see that this is actually in the Dorsal Stream
motion
Patients with Motion Agnosia (Akinetopsia) are able to perceive ___, and see the consequences of things that have moved, but are unable to perceive the ___ itself.
form // motion
True or False: Photoreceptors can code motion
False. Photoreceptors can code light intensity, but photoreceptors cannot code motion, therefore any motion signal that enters into our visual system must be calculated from the inputs of multiple neuron.
True or False: Perceiving motion is as simple as having an image move across the Retina, and then we perceive motion.
False: Visual motion is that perceiving motion is not as simple as having an image move across the retina and then we perceive motion.
What are the 5 other problems of visual motion?
- Apparent motion
- Induced Movement
- Motion Aftereffects
- Tracking a moving object
- Self-motion
What is Apparent Motion?
How when a still object changes position with just the right timing, we perceive it is moving from one position to another. This was discussed when we talked about Gestalt Psychology,
Anytime you are watching a video on a screen, this is always ___, it is the successive presentation of a bunch of still images, one after the other.
Apparent Motion
In Apparent Motion, the ___ is an important factor in how well the stimuli appears to move.
Interstimulus Interval (ISI)
What is the Interstimulus Interval (ISI)?
The Interstimulus Interval (ISI) is essentially the time between one still image and the next still image.
What does it mean if the Interstimulus Interval (ISI) is too short?
If the Interstimulus Interval (ISI) is too short, like if one frame is flashed very quickly after the previous frame, the images appear simultaneously.
What does it mean if the Interstimulus Interval (ISI) is too long?
If the Interstimulus Interval (ISI) gets too long, like if there’s too big of a pause between the different frames, it appears as successive still frames.
What does it mean if the Interstimulus Interval (ISI) is the right length?
As you make the Interstimulus Interval (ISI) slightly longer, you develop this partial perception of movement, then full illusory movement, like a flip-book.
Why do movies, video games, and other apparent motion stimuli seem so vivid and realistic?
The reason why movies, video games, and other apparent motion stimuli seem so vivid and realistic is because the visual system appears to code Apparent Motion and Real Motion in the same way.
What is Real Motion?
Real Motion is when the object is physically moving.
Example: Look down at your hand and wiggle it.
The brain cannot tell the difference between ___ and ___.
Apparent Motion // Real Motion because the brain
Why can we not tell the difference between Apparent motion and Real motion?
We cannot tell the difference between Apparent Motion and Real Motion because the brain can’t tell the difference, because of the way of visual neurons detect motion.
When subjects are shown Apparent Motion and Real Motion, what does the fMRI show?
The pattern of activation on the Retinotopic map is essentially identical.
All the neural explanations for why the visual system treats Real Motion and Apparent Motion the same focus around the ___.
Elementary Motion Detector
What is an Elementary Motion Detector?
An Elementary Motion Detector is a way in which visual signals from different photoreceptors can be combined to create a motion signal
A Reichardt Elementary Motion Detector occurs in the ___, and there’s evidence for this type of setup happening in ___ and ___.
Retina // Insects // Vertebrates
How does a Reichardt Elementary Motion Detector work?
Signals from A will be passed onto the interneuron, which has some Synaptic delay, and it will eventually project to the next neuron → B projects directly to the neuron → if both signals reach the Coincidence Detector neuron simultaneously it becomes activated → the Coincidence Detector passes its signal over to the direction-selective motion-detecting neuron.
What is Synaptic Delay/The Delay Stage?
Signals from A will be passed onto the interneuron, which has some Synaptic Delay, it takes a little while for the neurotransmitters to diffuse across the Synapse, and so sometimes this is referred to as the Delay Stage
What is a Coincidence Detector?
The neuron requires input from both of the synapses simultaneously in order to become activated, it requires CO-incident activation, and when this is activated to its certain threshold it will pass its signal over to the Direction-Selective Motion-Detecting neuron.
In a Reichardt Elementary Motion Detector, the two signals have to reach the neuron at the ___ time.
same/simultaneously/coincidentally
In a Reichardt Elementary Motion Detector, what is the function of the delay?
The delay allows the signals to meet at the same time, if there was no time, the signal from A would always hit first, and the signal from B would hit second, and that wouldn’t work out for the coincidence detector, that’s why this delay is required.
What are some features of a Reichardt Elementary Motion Detector
- Preferred feature size
- Space between A & B
- Delay
- Preferred speed (Velocity = Distance over time)
- Preferred direction
What would happen in a Reichardt Elementary Motion Detector that codes for L to R direction if the signal goes from R to L?
If Real or Apparent motion went from R to L, the signal would arrive first and then after a long delay the other signal would arrive, and then it wouldn’t activate the Coincidence Detector.
In a Reichardt Elementary Motion Detector, if we make the delay short, that means a real motion has to move from A to B ___ in order for there to be coincidence signals.
very quickly
In a Reichardt Elementary Motion Detector, if we set the delay to be very long, a ___ is required to get from A to B in order for the signals to reach the coincidence detector at the same time.
slow-motion
What is Induced Motion?
When we perceive motion when there isn’t motion. This is when the motion of one (usually larger one) object causes/induces the percept that another (usually smaller) object is moving.
When you have a moon-lit night and the clouds are racing by, people often report that the moon is moving quickly through the sky. What’s happening is that the clouds are being blown by the wind quickly in the other direction. What is this an example of?
Induced Motion
What is the Dot and Frame Illusion?
An example of Induced Motion where we have a dot which is stationary, and the frame moves back and forth, it can be perceived that the frame is stationary, but the dot is moving in the opposite direction.
In the Dot and Frame Illusion, if you move the frame to the right, one perceives motion of the spot to the ___.
left
What is Motion Aftereffect?
Where motion is perceived when there is no motion across the Retina is called the Motion Aftereffect.
What is Motion Aftereffect?
Where motion is perceived when there is no motion across the Retina
The Waterfall Illusion is an example of a ___.
Negative Motion Aftereffect
After staring at a waterfall for a long time, what do people often report?
They may notice that the ground looks like it’s moving or crawling upward due to the Aftereffect.
The direction of perceived motion after you’re looking at some stationary stimulus is in the ___ direction of the adapting motion.
opposite
The waterfall’s water is continuously falling downwards, so when you walk away and look at the stationary sidewalk, the sidewalk appears to drift ___, in the ___direction that the water was falling.
upward // opposite
How can the Waterfall Illusion or Negative Motion Aftereffect be explained?
This can be explained by having a balance in motion-coding neurons throughout the visual system.
When you’re looking at a stationary object with no adaptation under control conditions, the population of down cells should be ___ as the population of up cells.
about as active
When you look at a waterfall that is continuously moving downwards, the population of down cells, or in this case the down cell, becomes ___ and adapts, so the firing ___ a little bit. Up cells are inhibited by this, so they are ___.
really activated // decreases // silent
When you look away from the waterfall to the sidewalk, the Down cells in their adapted state, fire slightly ___ than their spontaneous rates. There’s some evidence that indicates that up cells fire slightly ___ than their spontaneous rate.
lower // higher
When you’re seeing a waterfall that’s moving downwards, the down cells are firing ___ than the up cells, and you are accurately perceiving the waterfall as moving downwards. But afterwards, because of this adaptation effect, when you look at a stationary object, these lingering adaptation effects cause the down-cell population to be slightly ___ than the up-cell population. So overall there is more ___ cell activity, and you perceive ___ motion when there is no motion at all.
more // lower // up // upward
If you stare at a moving stimulus for 30 seconds or so, then look at a stationary stimulus, you will see motion in the ___ direction
opposite
After removal of the waterfalls continuous movement, down cell’s firing rate ___ the spontaneous rate
falls below
