Researchers from the University of Massachusetts Medical School have shown—for the first time ever—that it’s possible to reverse an animal’s behavior by flipping around how one of its cells communicate.
The team turned to C. elegans, a nematode, in order to explore neuron signaling in depth. These nematodes have been extensively studied, to the point where their 302 neurons have a fully fleshed-out roadmap. (No other animal has a completely mapped neural wiring diagram.)
Researchers have also tied many of C. elegans’ behaviors to its neuronal roadmap, including an escape response activated by touching the front half of its body. The neural pathway involved in this response involves the actions of both excitatory and inhibitory neurons—cells that activate other neurons or hinder their actions. The pathway eventually leads to an inhibitory ion channel; once the inhibitory channel is activated, the nematode relaxes its head and changes directions in order to escape a predatory fungus.
Changing to excitatory receptor is exciting
The UMass group was curious as to whether changing this inhibitory receptor into an excitatory one—flipping its purpose completely around—would likewise reverse the nematode’s behavior. So they replaced the channel in a live nematode with an excitatory one to see what would happen, and got an exciting result.
“[W]e were able to completely reverse behavior by simply switching the sign of a synapse in the neural network,” explained co-author Dr. Alkema in a press release. “Now the animal contracts its head and tends to move forward in response to touch.”
Moreover, these results suggest that the neural structure is quite stable. “Surprisingly, the engineered channel does not affect development of and is properly incorporated into the neural circuits of the worm brain,” said Alkema.
Further, Alkema believes this may add to our understanding of evolution.
“Our studies indicate that switching the sign of a synapse not only provides a novel synthetic mechanism to flip behavioral output but could even be an evolutionary mechanism to change behavior,” he added. “As we start to unravel the complexity and design of the neural network, it holds great promise as a novel mechanism to test circuit function or even design new neural circuits in intact animals.”
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Feature Image: Wikimedia Commons
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