If humans or animals eat something that causes them to feel unwell, they subsequently avoid this food source. Until now, it has been unclear precisely how this avoidance learning takes place. A new study shows that communication between the brain cells and fat cells could play a crucial role here. The participants from the Universities of Bonn and Tohoku (Japan) and University Hospital Bonn have revealed the previously unknown mechanism in the fruit fly Drosophila. It may also exist in a similar form in mammals and even in humans. The results have now been published in the journal Neuron.