The role of dopamine in the brain has been redefined
Scientists at Vanderbilt University have proposed a new model of dopamine release in the brain.
American scientists have found that levels of dopamine, known as the “pleasure hormone,” are also increased by stress-related stimuli. According to the new model proposed by the researchers, the release of the neurotransmitter is a response to the novelty and significance of the stimulus. The Redefining Role of Dopamine is an article published in the journal Current Biology.
According to the reward prediction error theory, dopamine creates a strong sense of anticipation of the outcome. It is assumed that the levels of the neurotransmitter can track every mistake that a person makes in trying to get a reward.
In experiments on mice, rodents were offered “stick” (electroshock) and “carrot” (sucrose). By tracking dopamine levels in the nucleus accumbens with a genetically encoded sensor, researchers at Vanderbilt University have shown that neurotransmitter emissions cannot be explained solely by participation in the reward system. Scientists using machine learning technologies have built a model of the processes associated with the release of dopamine, and tested it using optogenetic experiments. According to her, the patterns of neurotransmitter release are consistent with signals about the novelty and significance of the stimulus.
Scientists emphasize that their discovery will force to rethink the way drugs work, which usually increase the level of dopamine in the brain. Therefore, it is likely that addiction models that rely on the notion of a “dopamine” reward system will have to be revisited.
A novel model of behavioral control: the Kutlu-CalipariSchmajuk (KCS) model These data show that theories used to explain dopaminergic information encoding do not hold up as predictive models of dopaminergic responses when they are pushed outside the narrow parameters they were originally designed to explain. Even more recent accounts of Pavlovian conditioning32,53 fall short, as they cannot explain concepts like latent inhibition and sensory preconditioning which have been shown to be directly altered by dopamine manipulations.54,55 To address this, we developed a new behavioral model, the KCS model – based on an earlier neural network model of Pavlovian conditioning (the SLGK model [56]) -, which allows unbiased mapping of dopamine onto its theoretical components (i.e., prediction error, association formation, attention, and temporal dynamics). This model is not only capable of describing our own findings but also explains why dopamine can be mistaken for an RPE signal when results from specific experimental conditions are considered in isolation. Importantly, we directly replicate and explain data that have formed the basis of support for RPE; thus, our results are not in conflict with prior data, but do show that this widely accepted theory is fundamentally incomplete. This work extends our current understanding and provides a new formalized theory for the role of dopamine in learning and memory.
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