Vision and Brain Workshop

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Vision and BrainWorkshop

• Jody Culham
• Canadian Association for Girls in Science
• November 19, 2005

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You see with your eyes

• and your brain!

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Much of the Brain is Devoted to Vision
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Vision is hard!
Which is harder to program, vision or chess?
1997 -- Deep Blue beats Kasparov
2??? -- A computer can perceive?!
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How much are you really aware of?

• Change blindness demo
• Simons door video

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The Brain Makes a Lot of Guesses

• Most of the time, the brain is smart and the
  guesses are right.
• Sometimes, under special circumstances, the
  guesses are wrong!
• ? Visual Illusions

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Visual IllusionsSometimes the brains vision is
wrong.
Which monster is bigger?
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Visual IllusionsSometimes the brains vision is
wrong.
Which monster is bigger?
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Very Big Kid
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Visual Illusions
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Visual Illusions
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Visual Illusions
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The Brain Can Be Fooled!

• Sometimes the brain can see several things

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Human Retina
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Blind Spot Demos
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Eye Movements

• People move their eyes about 3-4X per second
  (230,000X per day!)

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Color Afterimage
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Motion Aftereffect

• demo
• http//dogfeathers.com/java/spirals.html

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Motion Aftereffect
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Adaptation

• You stop noticing things that last a long time.
• This is why you dont usually see the blood
  vessels on your retina theyre always there!

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Afterimages and Aftereffects

• After looking at something for a long time, you
  see its opposite
• In the visual system, the opposite of green is
  red and the opposite of black is white
• The opposite of upward motion is downward motion

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Hollow Face Illusion
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Many Brain Areas
faces
places
bodies
objects
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Faces Are Special
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Faces Are Special

• We understand right-side-up faces much better
  than upside-down faces

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A Face Area in the Monkey Brain
An area of the monkeys brain that responds to
faces
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Face Blindness

• prosopagnosia
• some humans with brain damage cant recognize
  faces even though they can recognize objects

A face blind womans husband and how he looks to
her (from www.prosopagnosia.com)
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Strategies for Face Blind People

• use the voice, hair, clothes, movements
• guess based on the situation
• say hi to everyone

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Prosopagnosia Video
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How Can We Study the Human Brain?
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Functional Magnetic Resonance Imaging

• 4 Tesla fMRI Scanner, Robarts Research Institute,
  UWO

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MRI vs. fMRI
Functional MRI (fMRI) studies brain function.
MRI studies brain anatomy.
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Functional MRI
Big magnet (UWO magnet is 80,000X earths
magnetic field) radio waves
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MRI vs. fMRI
MRI
fMRI
one image

many images (e.g., every 2 sec for 5 mins)
? brain activity ? ? blood oxygen ? ?
fMRI signal
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Can You Read Cristianas Mind?
Whats going on in there?!
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She is looking at .. ?
face area
place area
Time (seconds)
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Guess what she is imagining?
face area
place area
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1.5
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Activation ( Change)
0.5
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-0.5
-1
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Time (seconds)
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The End