1. What the Frog Eye Tells The Frog’s Brain
We will talk about….
Kinds of visual information which may be useful for frog to survive
Four operations on the image in frog’s retina
How we can obtain information about these operations (from the frog)
What are advantages and disadvantages of such information processing
J.Y.Lettvin
H.R.Maturna
W.S.McCulloch
W.H.Pitts

2. Frog’s life Responds only to moving objects
Treats all small moving objects as food
Treats all large moving objects as enemy
On danger jumps to darker place
“Simple” non-adaptive requirements on visual system

3. Frog’s retina Ganglion cells Only one layer of ganglion cells
Enormous amount of overlap in input
Several types with distinct dendritic patterns
Very likely that there is some nontrivial processing

4. Most of described recordings:
Testing a Frog
Most of described recordings:
Done from optic nerve fibers
Used dull black disk as a moving object

5. Large Receptive Fields
4 “Basic” operations
small
receptive
fields
Sustained contrast detectors
Net convexity detectors
Moving edge detectors
Net dimming detectors
Large Receptive Fields

6. Sustained contrast detectors
Light intensity in receptive field
Ignores general illumination level
Responds similarly to large and small objects

7. Net convexity detectors
“Bugs detectors”
Ignores general illumination level
Responds only to objects which lie interior to receptive field

8. Moving Edge detectors Nearly ignores general illumination level
Responds to darklight AND to lightdark transitions
Frequency of discharge increases with velocity

9. Net dimming detectors Ignores general illumination level
Large receptive field
Response depends only on decrease of light in receptive field

10. Conclusion
Frog’s retina not just transfers but PROCESSES information, it calculates complex and important image properties including
Local sharp edges and contrast
Curvature of edge of dark objects
Movement of edges
Rapid local changes in light intensity
Each property decoded in distinct type of fibers of the optic nerve

11. Retina Higher brain levels Frog VS Human Low level implementation =
more effective, fast, BUT
non-adaptive, inflexible