What the Frog Eye Tells The Frog’s Brain

J.Y.Lettvin

H.R.Maturna

W.S.McCulloch

W.H.Pitts

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

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

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

Testing a Frog

Most of described recordings:

•Done from optic nerve fibers

•Used dull black disk as a moving object

4 “Basic” operations

•Sustained contrast detectors

•Net convexity detectors

•Moving edge detectors

•Net dimming detectors

small

receptive

fields

Large Receptive Fields

Sustained contrast detectors

Light intensity in receptive field

Net convexity detectors

“Bugs detectors”

Moving Edge detectors

Net dimming detectors

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

Frog VS Human

Retina

Higher brain levels

Low level implementation =

more effective, fast, BUT

non-adaptive, inflexible