Sense Of Smell: Loss Of Stimuli May Signal Increased Mortality Risk

Researchers at the Salk Institute for Biological Studies discovered a correlation between the loss of smell and declining lifespan in worms. Now, new research suggests that this may be an indicator of near death.

In this recent study, they conducted an experiment based on nematodes (Caenorhabditis elegans) that examined how they process information about the environment and how circuits in the brain change as an animal ages. The worms had 12 pairs of specialized neurons in its brain that detect stimuli in the environment.

Then, they measured the responses of all 24 neurons as C. elegans that were then exposed to benzaldehyde, a chemical that gives off a pleasant, almond-like smell. Scientists had previously identified individual pairs of these neurons as required for the animals to respond to attractive odors. They also divided the cells into both primary and secondary neurons.

"Primary neurons showed activity in response to the benzaldehyde, while secondary neurons responded to signals sent by the primary neurons. By having a neural circuit structured like this, the team hypothesizes, the worm can get better information on the strength or concentration of a smell," researchers said in a news release.

Lastly, the researchers measured how the circuit composed of primary and secondary neurons changed as C. elegans aged. As the primary neurons don't typically show a decline in activity, researchers discovered that secondary neurons became less active with age.

The study results seem to suggest that communication between the neurons may be degraded as animals age.

"There are a lot of questions that remain about what exactly is changing as an animal ages," Sarah Leinwand, first author of the study, said in a statement. "We want to keep looking at what is changing to cause some animals to have better functioning nervous systems and to live longer."

More information regarding the findings can be found in the journal eLife.

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