22. movement

Question 1

4 reasons movement is important?

Answer 1

1. you can see things you wouldn’t otherwise see
2. high sensitivity to biological motion
3. motion onset attracts attention
4. animate motion also attracts attention

Question 2

3 ways movement lets you see things you wouldn’t otherwise see?

Answer 2

1a. kinetic depth effect (structure from motion)
–> reveals 3D shape
1b. random dot kinematogram (hidden object)
1c. gradual/fuzzy contours disappear without retinal motion

Question 3

Kinetic depth effect def? AKA? Explain, example?

Answer 3

• “structure from motion”
• Motion reveals a 3D shape that you couldn’t previously see bc there were no/little other depth cues in the scene
• Ex. on youtube –> black image contour on white background, didn’t look like anything until it started to rotate and you could see what it was

Question 4

Random dot kinematogram meaning?

Answer 4

• an image of random dots with no defined shape in it
• a portion of the dots in a specific shape move, and you can identify the shape (ex. square)
• ex. in book was a fish blending into the sand, but you see it when it moves

Question 5

Gradual contours disappear without retinal motion meaning? What didn’t it apply to?

Answer 5

• focus on a single spot in the center
  –> eyes are usually moving at least a bit, this makes them stop as much as possible
• purple fuzzy dots around the edges fade until they disappear
• purple dot with black outline stays!

DOESN’T apply to RIGID borders
–> including the grey square background

Question 6

Neural explanation for gradual contours disappearing without retinal motion?

Answer 6

• eyes usually move –> neurons that detect edges would cross the fuzzy contours and detect them
• without movement, and no solid borders, neurons don’t see them, and they fade out

Question 7

Why are we sensitive to biological motion?

Answer 7

• we’re social animals
• being able to detect motion is a key part of communication with other people
• communication is essential for survival

Question 8

Evidence that we’re sensitive to biological motion?

Answer 8

1. point light walker
2. can detect bio motion with very low spatial frequency
3. human movement is very effective in advertisements

Question 9

Motion onset captures attention meaning? Evidence? Maybe reason why?

Answer 9

• people are very sensitive / pay attention when things START to move
• people were quickest to identify letter target when it began to move

Why? –> could be alive!

Question 10

Animate motion def? Why does it capture attention? Evidence?

Answer 10

• Animate motion = movement by something that’s alive
• It captures your attention bc its more likely to be relevant to your survival
• people pay more attention to spot showing animate (self controlled)

Question 11

How is a simple neural circuit to detect motion designed? Preferred…? (3 things)

Answer 11

• 2 neurons with diff. receptive fields link to one neuron (M)
• there is a delay in the connection between 1&M, but no delay between 2&M
• the delay means that the signal from 1 arrives at the same time as 2

^ this only works if the motion moves from the receptive field of 1 first and then 2 at the right speed

• M will have a preferred orientation, direction, and speed

Question 12

2 types of eye movements?

Answer 12

1. saccadic eye movements (or saccades)
2. smooth pursuit eye movements

Question 13

Saccadic eye movements (saccades) def?

Answer 13

Brief, rapid eye movements that change the focus of gaze from one location to another

Question 14

Smooth pursuit eye movements def?

Answer 14

Eye movements made to track a moving object or to track a stationary object while the head is moving

Question 15

Saccadic suppression def?

Answer 15

The visual system’s suppression of neural signals from the retina during saccadic eye movements

Question 16

Evidence that we take eye movements into account? (Afterimage)

Answer 16

• bright light –> afterimage on retina
• look around the room
• after image “moves” b/c you move your eyes
• RETINAL POSITION of the afterimage CAN’T change

–> eyes (and head) signal movement, but there’s no change on retinal stimulus
–> you see movement

Question 17

Eye movement experiment monkey –> what does it give support for?

Answer 17

• we take eye movement into account when perceiving motion
• we can distinguish between object moving / eyes still & eyes moving / object still
• retinal movement =/= perceived movement

Question 18

Eye movement experiment monkey –> what are the 2 set ups? What are the results (activity) ?

Answer 18

Version 1:
- monkey fixates straight ahead
- object moves through receptive field
- significant/high activity in neuron

Version 2:
- object is stationary
- monkey moves eyes from spot 1 –> 2
- monkey’s receptive field crosses over the object
- there’s some, but very limited activity, just above baseline

Question 19

Real-motion cells def?

Answer 19

• Neurons that signal actual movement of an object in the environment
• they combine retinal information with information about eye movements

Question 20

2 theories on how we account for eye movements?

Answer 20

1. Inflow
2. Outflow

Question 21

Inflow theory meaning?

Answer 21

• info about eye movement is sent from EYE MUSCLES (themselves) to the brain

Question 22

Outflow theory meaning?

Answer 22

• superior colliculus is responsible for telling the eyes when/how to move
• a COPY of those COMMANDS is sent from the superior colliculus to the brain
• COPY is called corollary discharge signal

Question 23

Corollary discharge signal?

Answer 23

• Copy of an eye-movement command from the superior colliculus (sent to other parts of the brain/visual system)
• informs visual system about upcoming eye movements
• ensures stable visual experience even during eye movements

Question 24

Important “assumption” to distinguish between theories? (when would we have info?)

Answer 24

INFLOW:
- says we ALWAYS have accurate info about the behavior and position of our eyes
- even if they’re doing something weird, we’d know

OUTFLOW:
- we ASSUME our eyes have ONLY done what we asked it to do based on CDS
- we would NOT know if they were doing something weird

Question 25

Inflow/outflow experiment 1: "Fixed objects, passive eye movements" What does this mean? What does each theory predict?

Answer 25

- objects in a room don't move - tap on eye to make it wiggle Inflow: you DON'T see movement, you know your eye is moving and account for it Outflow: you DO see movement, you can't tell your eye is moving Outflow :)

Question 26

Inflow/outflow experiment 2: "Fixed objects, paralyzed eye, _attempt_ to move eyes" What does this mean? What does each theory predict?

Answer 26

- objects in room don't move - eye is physically paralyzed - the person is trying to move the eye (ie. sending brain signals that the eye should be moving, but it's held in place) Inflow: DON'T see movement --> you know eye isn't moving Outflow: DO see movement --> you think your eye should be moving cuz your brain says so, you see the world as moving Outflow :)

Question 27

Inflow/outflow experiment 3: "Image _fixed on retina_, passive eye movements" What does this mean? What does each theory predict?

Answer 27

- Afterimage is used so it can be fixed on the retina - you tap your eye Inflow: DO see movement --> afterimage is fixed on retina, you know the retina is moving with the eye Outflow: DON'T see movement --> you didn't tell your eye to move, image is attached to eye --> no movement Outflow :)

Question 28

More evidence for outflow? Experiment?

Answer 28

Neurons with receptive fields can have anticipatory responses to stimuli in the NEW location --> where their receptive field is ABOUT to be, right after a saccade

Question 29

5 movement illusions?

Answer 29

1. movement after effects 2. aperture problem 3. apparent movement 4. induced movement 5. self-produced actions

Question 30

Movement aftereffect def? 2 examples?

Answer 30

- after viewing movement in one direction for a long time, if you look at a stationary object, it may appear to move in the OPPOSITE DIRECTION as the movement you were just observing - waterfall example - spiral example

Question 31

Neural explanation for movement aftereffect?

Answer 31

- circuit for movement requires the combination of 2 neurons --> the DIFFERENCE of the signals of the 2 make up the signal of the M neuron - when perceiving motion in one direction for long enough, one of the "feeder" neurons gets fatigued - after you look away from the motion, the fatigued neuron fires BELOW BASELINE --> RESULTING in a M neuron that gives the appearance of motion in the OPPOSITE DIRECTION

Question 32

Aperture problem meaning?

Answer 32

How can a cell (like one in V1) that only has a small receptive field ("aperture") and only sees movement in its _preferred direction_ detect 2 directional movement?

Question 33

Aperture problem solution?

Answer 33

The neurons that detect motion in MT have much larger receptive fields than the cells in V1 PATTERN cells combine info from V1 cells to determine the true direction of movement

Question 34

Component cells def?

Answer 34

Signal the direction of movement at a SINGLE contour (located in V1 and MT)

Question 35

Pattern cells def?

Answer 35

Combine information from different component cells (in V1 or MT) to get complete information about the direction of movement of an object

Question 36

Apparent movement def? Ex?

Answer 36

- 2 stimuli separated in TIME and LOCATION are perceived as a _single_ stimulus moving between the two locations - ex. 2 dots "moving" back and forth

Question 37

Bi-stable apparent motion (or quartet)

Answer 37

- symmetric kitty corner dots flip flop - you can see vertical or horizontal motion - covering half the dots can change the direction of movement

Question 38

Ternus display --> 2 types, what's the basic premise?

Answer 38

- there's 2 (or 3) dots - One is in the center, it never "moves," just blinks on or off - One is on the left, one is on the right ^^ L&R dots blink on ALTERNATING, so you only see 2 at a time Types: 1. Group motion 2. Element motion

Question 39

Ternus display --> Group motion What is it? When does it happen?

Answer 39

- you think there is a "group" of 2 dots that's being SHIFTED - you think the L dot becomes M dot, and M dot becomes R dot Happens when interval is LONG (>50ms)

Question 40

Ternus display --> Element motion What is it? When does it happen?

Answer 40

- you see middle dot staying STILL - outside dot is rapidly SWITCHING sides Happens when interval is SHORT (<50ms)

Question 41

Occluded jumping dot scenario?

Answer 41

- Theres a bunch of dots on the screen that are flickering to give the illusion of apparent motion - in one spot, one of the dots doesn't appear, because there is a red square in its place - instead of thinking there just wasn't a white blinking dot there, you perceive the white dot as moving BEHIND the red square

Question 42

Sort the following into a LOW level and HIGH level systems: a. element motion b. random dot kinematogram c. occluded jumping dot d. motion before form e. group motion f. form before motion

Answer 42

Low level: a. element motion d. motion before form b. random dot kinematogram High level: e. group motion f. form before motion c. occluded jumping dot

Question 43

Induced movement def?

Answer 43

- illusion where you think something is moving because its surroundings are moving Ex: - the dot moving up and down in the square moving in a circle looks like its also moving in a circle or diagonal shape - if a big semi truck next to you starts moving forward, you might think your car is slowly rolling backwards (self-induced motion)

Question 44

Self produced actions affect perceived movement meaning? Evidence for...?

Answer 44

- illusion where if you move your hand, you can change the direction you perceive movement - evidence that perception is tied to action