Take fruit flies, for example. Scientists at the Max Planck Institute for Neurobiology near Munich found the insects can override their survival instincts depending on how hungry they are.
Under normal circumstances, even low levels of carbon dioxide trigger an immediate flight reaction in all flies. But if the flies are hungry, the presence of the gas no longer seems to bother them as much.
Neurobiologist Ilona Grunwald-Kadow found that hungry flies repressed their urge to get away from carbon dioxide much quicker than flies which had recently eaten – but only if they could tell there was a meal on offer.
It seems that the danger signal is processed by different parts of the flies' brain depending on how hungry the fly is. By using a different part of the brain to process the signal, hungry flies were able to suppress their instinctive aversion to carbon dioxide.
“It is fascinating to see the extent to which metabolic processes and hunger affect the processing systems in the brain,” said Grunwald-Kadow.