When we smell something the scent triggers neurons in our brains that help us decide how to react but researchers how the brain processed multiple aromas at once.
A research team decided to turn to locusts to help answer their questions, a Washington University in St. Louis news release reported.
Locusts have "relatively simple sensory systems," making them easy to study. Barani Raman, PhD, of the School of Engineering & Applied Science at Washington University in St. Louis found the odors "prompted" neurons in the brain that allowed the locusts to identify each scent even if there were several present.
The researchers used a "computer-controlled pneumatic pump" to deliver a burst of scent to the insects. Locusts smell through olfactory receptor neuron located in its antennae. After the locusts experienced the scent they were given a piece of grass in an effort to achieve "Pavlovian conditioning." This phenomenon was noticed by researcher Pavlov, who rang a bell when he fed his dog. After some conditioning the dog would salivate at the sound of the bell.
Locusts don't drool, but they do open their mouth-parts when anticipating a meal. The team found the locusts would anticipate food when they smelled the scent even if a decoy scent was also released.
"We were expecting this result, but the speed with which it was done was surprising," Raman, said. "It took only a few hundred milliseconds for the locust's brain to begin tracking a novel odor introduced in its surrounding. The locusts are processing chemical cues in an extremely rapid fashion.
"There were some interesting cues in the odors we chose. Geraniol, which smells like rose to us, was an attractant to the locusts, but citral, which smells like lemon to us, is a repellant to them. This helped us identify principles that are common to the odor processing," he said.
The researchers are on a mission to understand olfactory computation and how it works.
"There is a precursory cue that could tell the brain there is a predator in the environment, and it has to predict what will happen next," Raman said. "We want to determine what kinds of computations have to be done to make those predictions."
The team hopes the study will answer other questions as well.
"Neural activity in the early processing centers does not terminate until you stop the odor pulse," Raman said. "If you have a lengthy pulse - [five] or 10 seconds long - what is the role of neural activity that persists throughout the stimulus duration and often even after you terminate the stimulus? What are the roles of the neural activity generated at different points in time, and how do they help the system adapt to the environment? Those questions are still not clear."
