Motion Perception Chapter 8 Lecture 14 Jonathan Pillow Sensation - - PowerPoint PPT Presentation

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Motion Perception Chapter 8 Lecture 14 Jonathan Pillow Sensation - - PowerPoint PPT Presentation

Oct 05, 2022 112 likes •458 views

Motion Perception Chapter 8 Lecture 14 Jonathan Pillow Sensation & Perception (PSY 345 / NEU 325) Fall 2017 1 (chap 6 leftovers) Defects in Stereopsis Strabismus eyes not aligned, so diff images fall on the fovea If not

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Motion Perception Chapter 8

Lecture 14

Jonathan Pillow Sensation & Perception (PSY 345 / NEU 325) 
 Fall 2017

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Strabismus

  • eyes not aligned, so diff

images fall on the fovea

  • If not corrected at an early

age, stereopsis will not develop stereoblindness: inability to use binocular disparity as a depth cue.

Defects in Stereopsis

(chap 6 leftovers)

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Müller-Lyer Illusion

http://www.michaelbach.de/ot/sze_muelue/index.html

Depth Illusions

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In which image are the two horizontal lines the same length?

(Ans: second from left)

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Two figures are the same size

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“Terror Subterra”

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“Terror Subterra”

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Depth / Size illusion

  • all 3 cars take up the same space in the image + on your retina!

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Binocular Rivalry

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Two stimuli battle for dominance of the percept

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  • monocular depth cues
  • binocular depth cues (vergence, disparity)
  • horopter
  • crossed / uncrossed disparities
  • free fusing
  • random dot stereogram
  • stereoscope
  • “correspondence problem”
  • panum’s fusional area
  • strabismus / stereoblindness
  • binocular rivalry (in book)

Chapter 6 Summary:

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Motion Perception Chapter 8

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Main point of this chapter: Motion = Orientation in Space-Time

time space

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which motion is faster?

time space time space

slow fast

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Real vs. Apparent motion

Apparent motion - motion percept that results from rapid display of stationary images in different locations

time space time space

apparent

(movies, flip-books)

“real” Q: why don’t we notice the difference?

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How does the nervous system encode motion? 
 What makes a Motion Receptive Field? Answer: a surprisingly simple neural circuit called a “Reichardt detector”

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Reichardt detector simple summing neuron

delay line

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space time

excitatory inhibitory

Reichardt detector in space-time first RF second RF 2nd neuron has a spatially separated Receptive Field (RF), and a shorter temporal delay

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space time

excitatory inhibitory

Smoother Reichardt detector Like an oriented V1 receptive field, but oriented in space-time!

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space time

excitatory inhibitory

Reichardt detectors respond to real and apparent motion

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Figure 7.3 Constructing a neural circuit for the detection of rightward motion (Part 1)

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Figure 7.3 Constructing a neural circuit for the detection of rightward motion (Part 2)

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Clockwise or Counter-clockwise rotation? (web demo)

Correspondence problem (motion): 


  • problem of knowing the correspondence between features in

successive frames 
 (which points in frame 1 are the same objects in frame 2?)

http://sites.sinauer.com/wolfe3e/chap8/correspondenceF.htm

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  • Aperture problem: 


when a moving object is viewed through an aperture, the direction of motion may be ambiguous

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  • Aperture problem: 


when a moving object is viewed through an aperture, the direction of motion may be ambiguous

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  • Aperture problem: 


when a moving object is viewed through an aperture, the direction of motion may be ambiguous

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  • this is a problem because each neuron only sees the scene

through a small aperture (its receptive field!)

  • how can the brain figure out the “global” direction of motion?
  • Aperture problem:

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aperture problem / correspondence problem

http://sites.sinauer.com/wolfe4e/wa08.02.html

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building a global motion detector

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Motion aftereffect (MAE): The illusion of motion that occurs after prolonged exposure to a moving stimulus http://www.michaelbach.de/ot/mot-adapt/index.html

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Motion after-effect

  • Always gives rise to motion in the opposite

direction of the adapting motion

  • Also known as: “waterfall illusion” -

stare at a waterfall; stationary objects will then appear to move upwards.

  • evidence for “opponent channels” in

processing motion

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Interocular transfer: The transfer of an effect (such as adaptation) from one eye to another


  • MAE: exhibits interocular transfer
  • Remember: Input from both eyes is combined in area V1

Q: What does this tell us about where in the brain motion is computed?

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“Motion After-Effect”

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“Motion After-Effect”

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