To identify the neural circuit which is responsible for motivation, the team used various techniques: First, a mathematical model was created which simulates the interaction of external and internal stimuli – for example the odor of vinegar and hunger.
In the next step, the neuroscientists of TUM identified the network of interest in the brain of the fruit fly in cooperation with colleagues in the USA and Great Britain. This was achieved with the help of electron microscopy as well as in-vivo imaging and behavioral experiments.
The result: The neural circuit of interest is located in the learning and memory center of the fly brain. It is controlled by the two neurotransmitters dopamine and octopamine, which is related to the human noradrenaline. Dopamine increases the activity of the circuit, i. e. increases motivation; octopamine reduces the willingness to make an effort.
“Since these neurotransmitters and the corresponding circuits also exist in the brains of mammals, we assume that similar mechanisms decide whether to continue or to stop”, concludes the neurobiologist. In the long term, the researchers hope that their findings will help to understand why the interaction of neurons and messenger substances in the brain, for example, in addictions gets out of control.
Reference: Sayin, S., Backer, J.-F. D., Siju, K. P., Wosniack, M. E., Lewis, L. P., Frisch, L.-M., … Kadow, I. C. G. (2019). A Neural Circuit Arbitrates between Persistence and Withdrawal in Hungry Drosophila. Neuron, 0(0). https://doi.org/10.1016/j.neuron.2019.07.028
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