Reliable and robust chemical sensing in diverse environmental conditions is needed by almost all living organisms for foraging food, finding mates and for survival. Biology solves this complex problem through the olfactory (sense of smell) and gustatory (sense of taste) systems. The question is can we use the biological olfactory system to our benefit?
The answer is we have been doing this since ages. We have used sniffer dogs for hunting and we use them now for extremely complicated tasks like bomb detection. But training a dog is very costly, time consuming and the performance is dependent upon the handler and dog’s emotional state. In our research, we are looking at the locust’s olfactory system for chemical sensing.
Through millions of years of evolution, insects have gained a finely tuned sense of smell. They can detect a variety of odors at very low concentration. Some of the other major advantages of using locusts as detection agents are that they are sturdy compared to other insects, cheap to breed and they can be sent into hostile environments. We also have a strong understanding of the locust’s olfactory system at the neuronal level.
The antennae of the locust contain Olfactory Receptor Neurons (ORNs) which generate an electric signal when activated by specific molecules. There are different types of ORNs which can bind to different molecules. These signals are carried into the Antenna Lobe (part of the locust brain) where they are processed. The Projection Neurons carry the processed information into the Mushroom Body which is considered to be associated with more complex tasks like memory and learning.
We are tapping into the signals generated by the projection neurons for odor classification. We will implant electrodes into brain of the locust, amplify and filter the readings and classify the odor that the locust is smelling. Current advances in electronics allow us to make miniature recording systems that can be mounted on the locust. The data from these systems can be wirelessly transmitted to a base location.
Locusts can be trained to identify certain odors through a process called Pavlovian conditioning. During the training period, an odor is repeatedly paired with a reward like food. This leads the locust to form an association between the odor and food. During testing phase, when the same odor is presented, the locust is now anticipating food and it will open its palps (appendages near the mouth parts) to let the food in. The Palp Opening Response can be considered to be indicative of the identification of the trained odor by the locust.