The combinatorial approach may be unique to this simple creature, Bargmann suggests, or it may be a clue to how higher organisms including humans solve the same problem: how a sensory system or another part of the brain can process a nearly limitless number of environmental cues with a finite number of nerves.
"We want to understand the relationship between genes, cells and behavior in the brain," she said, "but our own brains are complex beyond belief. In this fairly simple animal, we can decode the 'thinking strategy' used by every cell in the brain."
The research is published in the April 5 issue of Nature. Lead author is Paul D. Wes, PhD, a post-doctoral scientist in Bargmann's laboratory. (In a parallel paper in the same issue, a research group in Oregon found similar results in the worm's taste center, a system that is organized much like the taste system in humans.)
The worm in question is C. elegans, or more elegantly, Caenorhabditis elegans, a millimeter-long soil dweller widely studied by geneticists and developmental biologists because it displays many developmental processes and instinctive behaviors common to higher organisms. The worm is tiny and transparent, with a very small brain that can be studied in detail.
The key odors of interest in the UCSF study were benzaldehyde, which gives off a scent somewhat like almond, and butanone which has an oily smell. Both are thought to be produced by bacteria, the worm's food, but both can also be pervasive smells without useful information. Under those circumstances a sensible worm ought to ignore them, Bargmann said.
The scientists assayed a worm's ability to distinguish between the two odors by exposing it to a high concentration of butanone and then testing its ability to be attracted to benzaldehyde in this o
'"/>
Contact: Wallace Ravven
wravven@pubaff.ucsf.edu
415-476-2557
University of California - San Francisco
4-Apr-2001