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Cori Bargmann wants to know what it's like to be a worm.
An animal's behavior arises from the interplay between its environment, its experience and intrinsic properties of its neural circuits, according to Bargmann, the Thorsten N. Wiesel Professor at Rockefeller University. To understand how genetic networks help define the nervous system, Bargmann and colleagues study nervous system development and behavior in the nematode C. elegans, a common roundworm.
Bargmann, a former postdoctoral associate in biology at MIT, was the keynote speaker at the June 5-7 Picower Institute of Learning and Memory annual retreat in Falmouth, Mass. To be effective at teasing out the worm's behavior, she said, it helps to imagine what a worm's life in the soil is like.
Bargmann's laboratory explores whether the same basic motifs exist for behavior in worms and in humans. The roundworm, the fruit fly, the snail and the mouse are all models for human diseases and disorders, and it's important to know whether comparable genes and mechanisms are at work. "We're looking at ways more complex behaviors are assembled, and how pieces of information are put together in the nervous system to influence behavior," she said.
Each of C. elegans' 302 neurons and the junctions between them have been studied so exhaustively, "we should be able to understand what the molecules are doing, what the cells are doing to generate functional networks and how those networks lead to behavior," Bargmann said.
The worm is a simple organism, yet Bargmann has found that from a neurobiological point of view, it is much more "intelligent" than previously thought. Its system of attraction, avoidance and escape is much more sophisticated than one would expect, given its number of genes and proteins. Although it has a limited number of neurons, it packs a lot of receptors into each one, lending its molecular system "amazing complexity," Bargmann said, and the ability to "make fine discriminations about its world."
Roundworms have no circulatory or respiratory systems. They use chemo-sensory methods to detect whether the soil they live in is acidic or basic, has odors or contains heavy metals and oxygen. The worm can tell whether the bacteria it encounters are good to eat or will kill it or make it sick. The worm learns in a matter of hours to steer clear of a certain toxic soil bacteria -- a pathogen for humans as well as worms -- because, Bargmann speculates, when you only live for a short time, you can greatly increase your chances of reproducing if you can manage to stay alive for a few more days.
Bargmann has found that serotonin is required for learning -- without it, the worms didn't get repelled by bad bacteria, and in the presence of more serotonin, the worms learned faster.
The Picower Institute retreat featured scientific talks and poster sessions through which faculty, postdoctoral associates, graduate students, staff and collaborators from the Picower Institute and RIKEN Brain Science Institute of Japan built connections between laboratories and presented their research findings from the past year.
Other speakers at the retreat included Kazuo Okanoya from RIKEN, who spoke about why only a small subset of creatures -- humpback whales, songbirds and humans -- can learn to imitate sounds. These creatures are among the few who have the ability to incorporate external auditory stimuli into their own repertoire of sounds. Okanoya pointed out that this ability is related to a shared physiological feature: a direct pathway from part of the brain that controls movement to the part that oversees respiration and vocalization.