We rarely use just one sense at a time. Even when we eat, our experience is affected by a food’s look, feel, and smell, as well as its taste. Other creatures’ brains appear to be wired similarly.
Fruit fly larvae seem to integrate cues from multiple senses, too. For example, a larva is more likely to roll over to defend itself from a predator if it’s sensing a noxious stimulus – stinging, for example – and physical cues at the same time, according to findings from scientists at Janelia Research Campus.
Janelia Group Leaders Marta Zlatic and Albert Cardona led a team that mapped the neurons involved in this behavior. In a study published April 20, 2015, in Nature, the researchers mechanically stimulated fruit fly larvae while activating their nociceptor, or injury-sensing, neurons to understand the circuits involved from the point of stimulation to when the larva rolls over.
Surprisingly, they found that the circuits for nociceptive and mechanical stimulation were integrated on multiple levels, resulting in a very sophisticated structure. “Initially, I would have thought this circuit would be simpler, but the complex network could really allow the animal to do a complex computation and react to very particular combinations of cues,” says Zlatic.
The team has made its electron micrograph information freely available, with the hope that it will help in mapping the insect’s entire nervous system.