But determining how cells in the brain are physically connected is only the first clue for decoding our perceptions and behaviors. We also need to know the precise routes that information takes in the brain in a given context. Now, publishing their results September 8 in the journal
, researchers at the Salk Institute for Biological Studies have shown a striking example of the flexibility in neural circuitry and its influence on behaviors in worms, depending on the animals' environment.
The roundworm Caenorhabditis elegans
has exactly 302 neurons----far less than the estimated 100 billion neurons a person has----and we already know how each of them is connected. That, in addition to how easily the tiny creature's cells can be manipulated, allows researchers to ask what sort of information passes through the circuits----in molecular-and circuit-level detail----and what are the behavioral consequences of this information flow.
Even with a comprehensive map of the worm's neuronal connections in hand, however, scientists still don't know how the animal can interact with its environment in thousands of different ways. That's one big question that Sreekanth Chalasani, an assistant professor in Salk's Molecular Neurobiology Laboratory and Sarah Leinwand, a doctoral student at the University of California, San Diego, sought to answer.
In C. elegans
, thanks to studies performed more than 20 years ago, many sensory neurons were identified to have distinct roles such as sensing temperature, pheromones, salt and odors. To know what these cells did, scientists had zapped them one-by-one with a laser and measured the worms' behaviors. These studies implicated one neuron in the detection of increased salt in the worm's surroundings.