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Psych 126 > Lec 8 Motion > Flashcards

Lec 8 Motion Flashcards

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1
Q

Uses of visual motion:

A

recognize objects
distinguish depth
interact with environment
direct our attention

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2
Q

Uses of visual motion:

Object recognition

A

see structure from motion (variation in dot speed)

we recognize biological motion, walking

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3
Q

Uses of visual motion:

Depth- motion parallax

A

further slower, closer faster

insects use motion parallax to hunt, ex: bees and praying mantis

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4
Q

Uses of visual motion:

Depth- Camouflage

A

motion breaks camouflage

evolution of camouflage and detection of camouflage
Motion sensitivity improves ability to break camouflage

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5
Q

Uses of visual motion:

Depth- Common Fate

A

objects grouped by common motion

ie. a set of dots

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6
Q

Uses of visual motion:

Interacting with the environment: Optic flow

A

focus of expansion= direction of movement (getting closer= bigger, faster)

also used by bees, flies, zebra fish

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7
Q

Uses of visual motion:

Optic flow used in:

A

navigation

  • piloting plane
  • bees closer or farther from sides

posture

  • movement forward = everything expanding => fall forward
  • vection: perception of self-motion due to optic flow

judge time to collision (tau)
tau = distance r(t )/ velocity(t)
- when to catch ball
- diving gannets, pigeons, flies, infants

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8
Q

Uses of visual motion:

Attention

A

Motion grabs attention

blank screen blocks it

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9
Q

how do we know it is moving?

A

measured or position change?
evidence for low level detectors
- motion after aftereffect
- kinematograms

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10
Q

Explanation of Motion afteraffect

A

Pretest: Balanced Outputs- I & O neurons. no movement signal overall-> stationary

Adaptation: I Dominant signal-> Inward movement

Post-test: O Dominant signal (I- adapted) -> Outward movement

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11
Q

fMRI evidence from Motion Aftereffect

A

midialtemporal area MT

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12
Q

Kinematogram evidence against inferring motion from position change

A

Motion -> shape
perceive a shape that is defined by motion.
Not shape -> motion

disparity between time one and time two => motion, directly measured

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13
Q

How is motion directly measured/perceived?

A

Mechanisms in the retina Mechanisms in the visual cortex

Higher level mechanisms

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14
Q

How do we perceive motion:

retinal & cortical mechanisms

A

rightward motion neuron: two input simultaneously= rightward. the neuron on left is delayed. Will be simultaneous if the motion goes right if it intersects together.

delay that occurs after the first stimulation and the distance between the two neurons’ RFs determines the preferred speed of the directionally selective neuron

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15
Q

Reichardt detector

A

when a moving object is presented to two adjacent receptive fields sequentially.

But two stationary flashes of light should work just as well!

Examples of apparent motion:

  • Lights at the entrance of theaters
  • Vegas
  • Airport Runway lights
  • TV
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16
Q

Problems of motion: The aperture problem

A

Infinite family of directions produce indistinguishable motion within RF
-moving down or right of dashed lines.

Solving it:
- apparent speed & direction (velocity) of square as judged by two neurons
- avg velocity given by both neurons
Ex: (Component motions) Left + down => angular (pattern motion)

17
Q

MT neurons

A

prefer motion of patterns

will respond to V1 neurons, but not MT neurons

diamond #/ rotated # will respond to MT neurons but not V1 neurons

18
Q

MST

A 
Medial superior Temporal area
Large RFs, much larger than MT neurons
selective to optic flow patterns
-expansion
-contraction
-rotation
-shearing (parallel, moving right and moving left)
19
Q

High Level Motion Mechanisms

A

motion sensitive mechanisms in the retina and visual cortex.
-Direct measurement of motion, passive, based on luminance

20
Q

High Level Motion Mechanisms: Inferred motion- ambiguous motion

A

flicker grating motion
camouflaged spots motion
transformational apparent motion- - in H

21
Q

Attentive Tracking/ Multiple Object Tracking

A

parietal lobe

22
Q

Motion Blindness

A

inability to perceive continuous motion

bilateral damage to MT/MST

Psych 126 (7 decks)

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