Summer 1999
|
|
The little brightly colored car roaming across the floor of Shawn Lockery’s laboratory looks like the baby brother of NASA’s Pathfinder, the toaster oven-sized robot that rolled across the surface of Mars, beaming back to Earth those famous red-rock landscapes. But instead of extending our understanding of another planet, the vehicle in Lockery’s lab is exploring uncharted territory within the brain.
The car is a "biobot," a hybrid of biology and robotics.
The robotic elements are plain enough to see: a small electric engine, batteries for power, and a conventional steering mechanism. What has drawn so much attention to the biobot–including the cover story in a recent issue of Popular Science magazine and a feature article in the Washington Post–is its guidance system. Lockery and his associates have, in essence, been able to put the microscopic brain of a microscopic worm in the driver’s seat.
Over the years, this particular worm, a nematode known as C. elegans, has attracted a staggering amount of scientific attention.
"C. elegans has one of the least complex nervous systems of any life form on the planet," says Lockery, a University of Oregon biologist who has studied the worm for twenty years. "Its brain has only 302 neurons, or brain cells; that’s compared to about a hundred billion neurons in a human’s brain. It is the only animal for which we have a complete map of the brain. It is likely to become the first animal for which we can gain a fairly complete understanding of how the brain controls behavior."
One of the behaviors Lockery is most interested in–and which he and his coworkers have harnessed to drive the robot car–is the worm’s primitive feeding instinct. This instinct, technically termed chemotaxis, helps the worm zero in on likely sources of food. But in sharp contrast to a visually oriented human–who might spot a desirable apple, walk straight toward it, and take a bite–the worm sniffs out its food in a meandering, indirect manner. The scant information the worm’s tiny brain works with is similar to what a participant in the children’s game gets from the clue "warmer" when approaching the hidden object or "colder" when searching in the wrong direction.
"We have replicated the chemotaxis circuitry of the worm’s brain on a microchip," Lockery explains. "But we have made one switch. We made it so that instead of plotting a course to bring it closer to food, our robot searches out light."
Prominently placed on the front end of the car is a light sensor. It gathers information–"more light this way" or "darker over here"–and sends it to the microchip brain. The brain turns the information into action in the form of guiding the robot forward until new information suggests a change of course.
"The question of how the brain controls behavior is of immense scientific and medical interest," Lockery notes.
While some researchers are addressing the question by examining human brains with powerful tools such as magnetic resonance imaging (MRI), computerized axial tomography (CAT) scans and positron emission tomography (PET) scans, his laboratory is taking a different approach. By studying the worm’s rudimentary brain, his group is learning how a neural system works as a whole. Getting this fundamental grasp of how the system functions will be extremely helpful to other researchers working out the mechanics of more and more complex brains–all the way up to those in humans.
"A simple model, such as the worm’s brain, is a powerful research tool for learning about the role of whole systems as well as for studying the importance of individual molecules," Lockery says. "Researchers trying to unravel the complex chemical and molecular bases of diseases such as Alzheimer’s need a precise understanding of how individual molecules affect the brain. This kind of understanding will come from investigating simple model systems like the worm."
Aside from the biomedical advances associated with brain research, Lockery’s biobot may also have some very practical applications. The U.S. Navy is funding some of this research out of an interest in developing improved minesweeping methods to make shipping and amphibious landings safer. Artificial fish using a biochip programmed to home in on faint traces of explosives could be released into a mined harbor. Upon finding the mine, the fish could emit an alert signal and serve as a beacon for mine-clearing activities.
With a variation in programming, these robotic fish could be useful in environmental cleanup by zeroing in on oil or chemical spills.
"The idea of learning from nature makes a great deal of sense," Lockery says. "Evolution has been at work improving these brains for millions of years while we’ve only been designing chips for a few decades."
The robotic car has gone through a rapid evolution of its own. Early contributions by postdoctoral research fellow Thomas Ferree helped get an early prototype rolling back in 1997. Tom Morse, another postdoctoral fellow who continues to work on the biobot project, collaborated with Lockery on the programming and construction of more advanced models.
"Through the development of this car we now understand much better how the worm’s 302 neurons work together," Lockery says. "The next step is to build on what we’ve already discovered to come to a fuller understanding of how they function individually. The car is the perfect (pardon the pun) vehicle for that research."