hybrid vigor | muscle man

Muscle Man

by Andrew Procter

At first glance, an olive jar in Dr. Darrell Stokes' office seems to live up to its label. The contents are round, greenish-yellow, and floating in some sort of preservative. But step closer and you realize they are roaches. Big ones.

"People think I work with cockroaches, and I say, 'No, I work with muscles,'" says Stokes, 62. Roaches' muscles are remarkably easy for use in experimentation. Unlike a human muscle, which is innervated by many nerve cells, a cockroach muscle is innervated by one, an advantage when you are doing electrical recordings from single nerves.

Dr. Stokes has studied mechanical and neural design in the muscles of roaches and other arthropods, including beetles and crabs. Generally, these invertebrates have simpler muscle organization than vertebrates, making them easier to study. Stokes discovered this line of research as a grad student. "I got interested in the physiological basis of behavior, and the things that make organisms behave are muscles," he explains.

One of his postgraduate projects investigated the extent to which cockroach leg motions are controlled by central versus peripheral nerve circuits. Located in collections of neurons called ganglia, the central circuits program the basic pattern of locomotion. The peripheral circuits, found in the muscles and exoskeleton, send the central circuits feedback information about limb position, muscle length and muscle tension. Such feedback can modulate the central program in a way Stokes compares to a record player: "It's set to run at a certain speed so the sound is recognizable. But if you put your finger on the record, you can slow it down."

In the experiment, Stokes places the cockroaches on a circular track, then performs live electrical recordings from their leg muscles as they scurry around. At the same time, he films the roaches at 500 frames per second to map nerve signals against limb positions. Since the roaches have three legs on the inner track and three legs on the outer track, the two sets of legs have to move at different speeds to stay on the curve. Stokes determined that this feat requires modification of the central motor program, which is identical for both sides. The experiment also works in reverse: "We could take partially dissected roaches, feed the electrical inputs into their muscles and record the power output." But success came slowly. "We were lucky if we could do one or two experiments a day," he said.

Funded by the National Science Foundation, his research has many applications outside animal behavior. "The Navy is very interested in locomotion, primarily as it relates to robotics," Stokes remarks. Insect research has been applied to small robots, which could carry out risky missions such as diffusing bombs. Muscle research also has applications in prosthetics. Understanding how nerve signals produce locomotion could lead to artificial, electrically-stimulated walking in quadriplegics. "You take people with damaged nervous systems, whose muscles can no longer receive the appropriate signals, and computers are used to organize contraction in a sequential manner," Stokes explains.

Dr. Stokes' research has taken him across the globe. After undergraduate study in Minnesota, he did graduate work in Hawaii and postgraduate work in California and Japan. Much of his published work is based on his summer research over the years at the Woods Hole marine biology lab in Massachusetts. "You do one study, you ask a certain question, and in answering it, you come up with 10 more questions. That's the way science operates," he says. Now in his 30th year at Emory, he is considering retirement within a few years and has already begun phasing out his lab.

Still, he has not managed to avoid roach troubles of his own. What's the best way to get rid of roaches? "Spread boric acid across the threshold of your house," suggests Stokes. "Cockroaches are fastidious--they pick up the boric acid crystals to clean themselves, then they ingest them and it kills them." But the relationship's not all bitter. Despite phasing out his lab, he's holding onto some prized specimens. "I can't bring myself to get rid of them," he said.


	Muscle Man by Andrew Procter At first glance, an olive jar in Dr. Darrell Stokes' office seems to live up to its label. The contents are round, greenish-yellow, and floating in some sort of preservative. But step closer and you realize they are roaches. Big ones. "People think I work with cockroaches, and I say, 'No, I work with muscles,'" says Stokes, 62. Roaches' muscles are remarkably easy for use in experimentation. Unlike a human muscle, which is innervated by many nerve cells, a cockroach muscle is innervated by one, an advantage when you are doing electrical recordings from single nerves. Dr. Stokes has studied mechanical and neural design in the muscles of roaches and other arthropods, including beetles and crabs. Generally, these invertebrates have simpler muscle organization than vertebrates, making them easier to study. Stokes discovered this line of research as a grad student. "I got interested in the physiological basis of behavior, and the things that make organisms behave are muscles," he explains. One of his postgraduate projects investigated the extent to which cockroach leg motions are controlled by central versus peripheral nerve circuits. Located in collections of neurons called ganglia, the central circuits program the basic pattern of locomotion. The peripheral circuits, found in the muscles and exoskeleton, send the central circuits feedback information about limb position, muscle length and muscle tension. Such feedback can modulate the central program in a way Stokes compares to a record player: "It's set to run at a certain speed so the sound is recognizable. But if you put your finger on the record, you can slow it down." In the experiment, Stokes places the cockroaches on a circular track, then performs live electrical recordings from their leg muscles as they scurry around. At the same time, he films the roaches at 500 frames per second to map nerve signals against limb positions. Since the roaches have three legs on the inner track and three legs on the outer track, the two sets of legs have to move at different speeds to stay on the curve. Stokes determined that this feat requires modification of the central motor program, which is identical for both sides. The experiment also works in reverse: "We could take partially dissected roaches, feed the electrical inputs into their muscles and record the power output." But success came slowly. "We were lucky if we could do one or two experiments a day," he said. Funded by the National Science Foundation, his research has many applications outside animal behavior. "The Navy is very interested in locomotion, primarily as it relates to robotics," Stokes remarks. Insect research has been applied to small robots, which could carry out risky missions such as diffusing bombs. Muscle research also has applications in prosthetics. Understanding how nerve signals produce locomotion could lead to artificial, electrically-stimulated walking in quadriplegics. "You take people with damaged nervous systems, whose muscles can no longer receive the appropriate signals, and computers are used to organize contraction in a sequential manner," Stokes explains. Dr. Stokes' research has taken him across the globe. After undergraduate study in Minnesota, he did graduate work in Hawaii and postgraduate work in California and Japan. Much of his published work is based on his summer research over the years at the Woods Hole marine biology lab in Massachusetts. "You do one study, you ask a certain question, and in answering it, you come up with 10 more questions. That's the way science operates," he says. Now in his 30th year at Emory, he is considering retirement within a few years and has already begun phasing out his lab. Still, he has not managed to avoid roach troubles of his own. What's the best way to get rid of roaches? "Spread boric acid across the threshold of your house," suggests Stokes. "Cockroaches are fastidious--they pick up the boric acid crystals to clean themselves, then they ingest them and it kills them." But the relationship's not all bitter. Despite phasing out his lab, he's holding onto some prized specimens. "I can't bring myself to get rid of them," he said.