What the Frogs Eye Tells Its Brain

1
What the Frogs Eye Tells Its Brain

• Or, How a Frogs Brain Constructs Its Visual
  World.

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Receptive Fields

• Receptive fields
• On Center Off Surround
• Off Center On Surround
• Diagramming neural circuits
• Retinal circuitry
• Operation of an edge detector

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Edge Detectors

• Lateral inhibition and edge enhancement
• Demonstrations http//dragon.uml.edu/psych/illus
  ion.html
• Lateral inhibition simulator
• http//serendip.brynmawr.edu/bb/latinhib_app.html

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Types of Detectors

• Boundary Detectors
• Ex one group responds to horizontal border that
  is darker below and lighter above (surface of
  pond detector?)
• Concave Boundary Detector
• Activated by concave line moving in the direction
  of concavity (big mouth bass detector?)
• Changing Contrast Detector
• Responds most to high contrast edge moving fast
• Dimming Detector
• Responds to slowly changing brightness

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Types of Detectors

• Bug detector
• Small, dark, moving spot detector
• Frogs eat live flies but will starve to death on
  a pile of dead ones
• Frogs visual system may actually be so primitive
  that stationary objects actually disappear. (Of
  course humans cant see a deer in the woods until
  it moves, either)

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More Complex Detectors

• Newness Neurons
• Adapt immediately to movement in a particular
  direction but still respond to movement through
  their fields in a new direction
• Sameness Neurons
• Larger fields do not respond immediately to an
  object brought into the field, but once they
  notice it they respond to it as long as it
  stays in the field, with stron g bursts taking
  place every time it starts to move or change
  direction (looses it if stationary for 2 min)

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More Complex Detectors

• Straight Line Detectors
• Movement Detectors
• Direction Detectors

8
Cortical Cells

• Simple Cortical Cells
• Complex Cortical Cells
• Binocular Disparity detector
• Novelty detector
• Columnar organization