Recognising Rewards

Responding appropriately to pleasant or unpleasant events, in scientific terms rewarding or aversive stimuli, is critical for our health. Neurons in a part of the brain called the dorsal raphe nucleus (DRN), that produce the neurotransmitter serotonin, play a key role in signalling reward. Yet drugs boosting serotonin levels do not restore rewarding feelings in patients with depression, suggesting additional pathways are also involved. In mice, other serotonin-producing neurons, in the median raphe nucleus (MRN), appear to have opposite effects to the DRN: rewarding stimuli inhibit MRN neurons, and stimulating them triggers negative responses. To measure mouse perception, scientists monitored their behaviour and facial expressions; as shown here, mice move their tongue and ears when enjoying a sugar solution, but stimulating MRN neurons dampens this response, suggesting their perception of reward has changed. Understanding this interplay between serotonin pathways will be crucial to developing better treatments for disorders like depression.

Written by Emmanuelle Briolat

Emmanuelle Briolat

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A researcher specialising in visual signals in Lepidoptera, camouflage and the effects of light pollution, Emmanuelle’s writing covers a range of topics, from biomedical research to children’s books about moth defences.

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• Image from work by Hiroyuki Kawai and Youcef Bouchekioua, and colleagues
• Department of Molecular Pharmacology, Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto & Department of Neuropharmacology, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan
• Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)
• Published in Nature Communications, December 2022