Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: FRIDAY, November 10, 1995 TAG: 9511100098
SECTION: NATIONAL/INTERNATIONAL PAGE: A-9 EDITION: METRO
SOURCE: JANE E. ALLEN ASSOCIATED PRESS
DATELINE: LOS ANGELES LENGTH: Medium
Locusts - and probably other creatures - use complex mathematics in their eyes and brains to sense that an approaching object is getting too close and that it's time to get out of the way, scientists say.
The finding someday might be used to build an artificial human retina that would send signals to help blind people avoid bumping into things, said Gilles Laurent, an assistant professor of neuroscience at the California Institute of Technology in Pasadena.
Such technology is probably a decade off, he said.
Laurent is part of a team of scientists who found a mathematical function that explains how a locust's brain processes the size and speed of a potential threat. Their study appears in Friday's issue of the journal Science.
``Detecting predators or detecting danger is a very general problem in nature, and it concerns all animals, including us when we cross the street. We have to be able to detect that a car, for example, might hit us,'' Laurent said Wednesday. ``The problem is to first recognize that an object is approaching, and the second is to react before it actually collides.''
He explained that the retina provides three pieces of critical information about an approaching object: the size of the image, the speed at which its edges are widening and how much the image is speeding up.
To find out what makes the locust act before the moment of impact, scientists put the 2-inch insect in front of a computer screen, covered one of its eyes and projected images that simulated an approaching object. The scientists recorded via an electrode how one single neuron, or brain cell, pulsed in response to the visual stimulus.
Scientists found a mathematical quantity that peaks before the moment of impact and apparently triggers a warning to get out of the way, Laurent said.
However, ``if the approach of the object is too fast,'' he said, ``the reaction time is not long enough and the animal gets hit. That's why predators can survive. Nature evolves some sort of equilibrium so prey can avoid predators most times, but sometimes get eaten so predators themselves can live.''
Laurent said that although he's not an engineer, he could foresee a human vision system using a silicon-chip retina now being developed at Caltech.
The retina, he said,would use principles derived from his experiment.
It would ``combine inputs about the size of what it sees and the velocity of what it sees in a way that would allow a signal to be generated prior to an impending collision,'' he said.
by CNB