Everyone has scents that naturally appeal to them, such as vanilla or coffee, and scents that don’t appeal. What makes some smells appealing and others not?
Barani Raman, PhD, a professor of biomedical engineering at the McKelvey School of Engineering at Washington University in St. Louis, and Rishabh Chandak, who earned bachelor’s, master’s and doctoral degrees in biomedical engineering in 2016, 2021 and 2022, respectively, studied the behavior of the locusts and how the neurons in their brains responded to appealing and unappealing odors to learn more about how the brain encodes for preferences and how it learns.
The study provides insights into how our ability to learn is constrained by what an organism finds appealing or unappealing, as well as the timing of the reward. Results of their research were published in Nature Communications Aug. 5.
Raman has used locusts for years to study the basic principles of the enigmatic sense of smell. While it is more of an aesthetic sense in humans, for insects, including locusts, the olfactory system is used to find food and mates and to sense predators. Neurons in their antennae convert chemical cues to electrical signals and relay them to the brain. This information is then processed by several neural circuits that convert these sensory signals to behavior.
Raman and Chandak set about to understand how neural signals are patterned to produce food-related behavior. Like dogs and humans salivating, locusts use sensory appendages close to their mouths called palps to grab food. The grabbing action is automatically triggered when some odorants are encountered. They termed odorants that triggered this innate behavior as appetitive. Those that did not produce this behavior were categorized as unappetitive.