Ever wondered why when you see a fly at the dinner table it hovers backwards and forwards, before settling on your favourite part of the dinner?
It clearly has been bothering Preethi Sareen, associate research scientist of cellular and molecular physiology, genetics, and neuroscience at Yale School of Medicine in New Haven, Connecticut.
She claims to have made a discovery and it could have implications for humans.
Flies, like humans, have discriminating taste. They spend much of their time seeking sweet, nutritious calories and avoiding bitter, potentially toxic food, so the researchers decided to trick them.
They gave hungry fruit flies a choice between sweet, nutritious food laced with bitter quinine and a less sweet, but not bitter, food containing fewer calories. Then, using neuroimaging, they tracked neural activity in their brains as they made these tough choices.
Which food was chosen?
“It depends on how hungry they are,” Michael Nitabach, professor of cellular and molecular physiology, genetics, and neuroscience at Yale School of Medicine and senior author of the study, told ScienceDaily.
“The hungrier they are, the more likely they will tolerate bitter taste to obtain more calories.”
However, the real answer to why the fruit flies make their choice is a little more complex, and that’s where it gets interesting for humans, according to the study in Nature Communications earlier this month
Ms Sareen said flies relay sensory information to a portion of their brain called the fan-shaped body, where signals are integrated, triggering what amounts to the insect version of an executive decision. The researchers found that patterns of neuronal activity in the fan-shaped body change adaptively when novel food choices are introduced, which dictates the fly’s decision over what food to eat.
Inducing a change in behaviour
The researchers went a step further. And things got even stranger.
They found they could change a fly’s choice by manipulating neurons in areas of the brain that feed into the fan-shaped body. For example, when they caused a decrease in activity in the neurons involved in metabolism, the found that it made hungry flies choose the lower calorie food.
Neural activity in both a fly’s brain and a human’s brain are regulated by the secretion of neuropeptides and the neurotransmitter dopamine, which in humans helps regulate sensations of reward.
Changes in this network may alter how the brain responds to different types of food. In other words, neurochemistry may sometimes dictate food choices we think we are making consciously.
“The study provides a template to understand how it is that things like hunger and internal emotional states influence our behaviour,” Professor Nitabach said.
