How worm knows where its nose is

London, May 17: Worms’ nervous system is much more capable and complex than previously thought, and has a way to monitor its own motion, a new Harvard study has suggested

The model one day could serve to develop treatments for disorders like schizophrenia.





In the interneurons that the researchers study, named RIA, the worms use these local activities to encode “corollary discharge” – a phenomenon in which motor neurons send a “copy” of a motor instruction back to the central nervous system – to monitor their body position and guide their movement about their environment.

“The simplest behaviors to understand were the first ones that were studied in C. elegans – something painful happens and it backs up,” explained Michael Hendricks, a research associate and co-author of the paper.


Zhang said, “What we found is that, in some neurons, the synapses are highly organized at the sub-cellular level, and that organization is associated with local neural activity.”


“Why is that important? C. elegans has only 302 neurons. Before, people simply thought each neuron was one functional module, so all the brain’s computations depended on those modules. What we found is that there are, potentially, many more functional units. That hugely enlarges the computational capability of this relatively simple neural system,” she added.


The worms typically interact with their environment by sweeping their head back and forth to collect sensory input, such as odor and salt. The corollary discharge is critical because it allows the worms to know how much they have turned their head in a particular direction, and to use this information together with the sensory input to direct their next move.

“Corollary discharge is the reason you can’t tickle yourself. You’ve already sent a copy of the motor command back to your brain telling it what you’re doing. The fact that this phenomenon takes place in a creature like C. elegans is important because it’s been hypothesized that the voices and delusions of people suffering from schizophrenia may be related to impairment in this system,” Zhang explained.

By studying that system in C. elegans – how it works, how it can be damaged, and how it might be repaired – Zhang said researchers will be able to gain more understanding on neurological disorders, such as schizophrenia, which may help with ways for treatments.

For now, though, the next step for Zhang is to probe potential compartmentalized activity in many other worm neurons, to understand how such compartmentalized activity is related to learning and what the effects of altering the corollary discharge system might be.

The work is described in a paper published on May 13 in Nature. (ANI)