A bat's brain can resolve sonar images up to threetimes more sharply than biologists had previously thought and much better than man-made equipment. The findings, described in the current issue of the journal Proceedings of the National Academy of Sciences, may lead to improved sonar for naval and other uses.

The new view of bats comes from research at Brown University that suggests the mammal's sonar images are of a higher quality and are suited to a wider variety of orientation tasks than just catching insects. The processing of sonar echoes in the bat's brain is correspondingly more sophisticated than had been suspected.

In experiments, bats separately perceived and processed overlapping echo delays arriving as little as two microseconds - two thousandths of a second - apart, an ability roughly three times keener than scientists had believed was possible in the mammals.

This fine-tuned capability, based in the bat's nervous system, allowed the animals to resolve echo-reflecting points on an object as close together as three-tenths of a millimeter, about the width of a pen line on paper. Such image resolution is significantly better than any man-made sonar, say the study authors.

"Using the same sounds as the bat, the best man-made sonar equipment can only process echo delays arriving five to 10 microseconds apart," said study leader James Simmons, professor of neuroscience in the Brown University School of Medicine. "The experiments showed that a bat's sonar resolved echoes that arrived two microseconds apart as easily and routinely as if there were 10 microseconds between them." Simmons and colleagues have also begun experiments to record neural responses in bat brains that may account for the superior sonar resolution. The scientists are using the new resol
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Contact: Scott Turner
Scott_Turner@Brown.edu
401-863-1862
Brown University
13-Oct-1998