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Compiled from reports by Rob Stein
Monday, November 20, 2000; Page A09

3 New Primate Species Found

An international team of scientists has discovered three previously unknown species of primates in the forests of Madagascar.

The species are mouse lemurs, the world's smallest primates. They are primitive, nocturnal creatures that live in trees and are found only on the island of Madagascar and the nearby Comoro islands off the coast of Africa.

There are about 40 known species of living lemurs, but more than half are endangered because their forests have been destroyed by Madagascar's rapidly growing population.

Steven Goodman of the Field Museum in Chicago, Jorg Ganzhorn of the University of Hamburg in Germany and Rodin Rasoloarison of the University of Antananarivo in Madagascar identified the new species during a recently completed survey of mouse lemurs in the island's western forests.

Based on their physical characteristics, the researchers concluded there were seven species, including three that had never been documented. They dubbed them Microcebus berthae, Microcebus sambiranensis and Microcebus tavaratra.

"It's incredibly rare to describe a new species of primate, let alone three," Goodman said in a statement last week.


Robotic Promise for Paralysis

Scientists have found a way for monkeys to control a remote, robotic arm with their brain signals, an advance that may eventually lead to new ways to help paralyzed people.

Miguel Nicolelis of Duke University Medical Center in Durham, N.C., and colleagues implanted dozens of hair-thin electrodes into the brains of two owl monkeys and recorded electrical firing patterns as the monkeys did various tasks, including reaching for food. The researchers then fed the recordings into a computer to analyze which firings were involved in controlling the monkeys' arms.

As the monkeys moved, the researchers fed the brain signals they had determined controlled the movement into two robotic arms--one in the same room and another at the Massachusetts Institute of Technology in Cambridge, Mass., that was fed instructions over the Internet.

"It worked out beautifully," said Mandayam Srinivasan of MIT. "It was an amazing sight to see the robot in my lab move, knowing that it was being driven by signals from a monkey brain at Duke. It was as if the monkey had a 600-mile-long virtual arm."

The researchers, who reported their work in Thursday's issue of Nature, hope to use the results to develop ways for paralyzed people to control robots with their brain signals.

"The idea of driving robotic limbs with what effectively amounts to the mere 'power of thought' was once in the realm of science fiction," wrote Sandro Mussa-Ivaldi of Northwestern University Medical School in Chicago in an accompanying article. "But this goal is edging closer to reality."


Narrowing Pyramids' Birth Date

A British researcher thinks she has narrowed the date when ancient Egyptians built the pyramids.

Kate Spence of the University of Cambridge analyzed the relative positions of the Earth and two stars, which, she hypothesized, the pyramids' builders used to align the massive structures with true north. What today is called the North Star would have been in the wrong position back then.

The stars are Kochab, which is in the bowl of the Little Dipper, and Mizar, which is in the middle of the handle of the Big Dipper. Based on when they would have been in position to align the pyramids, construction would have begun within five years of 2467 B.C., Spence concluded.

Previous estimates on when the mammoth construction project began were accurate only to within about 100 years.

"Spence has come up with an ingenious solution to a long-standing mystery," wrote Owen Gingerich of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., in an article accompanying the research in Thursday's issue of Nature.


Imagination's Neural Map

To find out more about how the human brain produces the "mind's eye," scientists have for the first time directly measured brain cells in people as they imagined objects.

Researchers from the University of California at Los Angeles and the California Institute of Technology studied nine epileptic patients who were undergoing surgery to try to determine what parts of their brains were causing their seizures.

Using microelectrodes, the researchers recorded the activity of 276 brain cells in parts of the patients' brains involved in memory and social behavior while they imagined objects they had seen, such as cars, animals, food and famous people.

Single neurons in certain parts of the brain--the hippocampus, the amygdala, the entorhinal cortex and the parahippocampal gyrus--fired about the same as when the patients were actually seeing the objects, the researchers reported in Thursday's issue of Nature.

"Our study reveals that the same brain cells that fire when a person looks at a picture of the 'Mona Lisa' are, in fact, the same neurons that excite when that person is asked to imagine the 'Mona Lisa,' " said Itzhak Fried of UCLA.

© 2000 The Washington Post Company