Until now, it was thought that dopamine, the “pleasure molecule”, was mainly involved in the reward circuit linked to positive experiences. A new experiment carried out on volunteer patients has just shaken up this belief.
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When you eat a pan of very good chocolate, the great cocoa lover that you are can feel a rush of pleasure and well-being. Consequence: you want to have more. This desire is induced by the production of dopamine by your brain, a neurotransmitter involved in particular in the regulation of mood, movement or the reward circuit.
This circuit pushes us to voluntarily perform actions that are more or less essential to our survival by producing the famous “pleasure molecule”: eating, drinking, making love, having a social life, reading, listening to music, etc. It is also implicated in addiction issues. Until now, we thought that its role was to learn through pleasure, but an experience reported in a study published on 1er December in Science Advances could shake up everything we thought we knew.
The experience: a world first
Researchers from the Wake Forest University School of Medicine showed that the release of dopamine in the human brain is also involved in the process of learning from negative experiences, allowing the brain to adjust and adapt its behavior based on the results of these experiences. To reach this conclusion, scientists inserted a carbon fiber microelectrode into the brains of three volunteer participants who were scheduled to undergo brain surgery to treat essential tremor.
These patients were then asked to play a computer game in which their choices were either rewarded or punished with actual monetary gains or losses. The game was divided into three stages at the end of which participants learned, through positive or negative feedback, to make choices that maximized rewards and minimized penalties. Dopamine levels were measured continuously, once every 100 milliseconds, during each of the three stages of the game.
Better understand psychiatric disorders
“We found that dopamine not only plays a role in signaling positive and negative experiences in the brain, but that its production is optimal when trying to learn from those outcomes, enthuses Professor Kenneth T. Kishida, associate professor of physiology and pharmacology and neurosurgeon at the Wake Forest University School of Medicine, in a press release. What’s also interesting is that it seems that the dopamine system takes different pathways in the brain depending on whether the experience is rewarding or punishing.
According to the researcher, this experiment – the first to directly measure the dopaminergic activity of the human brain – could make it possible to “better understand the mechanisms underlying depression, addiction and related psychiatric and neurological disorders”.
