[Research](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7804370/): Dopamine, Prediction Error and Beyond (2021) * **Dopamine** neurons serve a general function in signaling the expectation of (any) information or signaling errors in any type of prediction where value is only one of the dimensions. **Dopamine** codes the precision (uncertainty) or reliability of the **prediction error (PE)**. These models also directly link perception and beliefs with both engaged in making sense of inputs by inferring their causes * **Dopamine** codes [prediction error](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7804370/figure/fig6-1073858420907591/) size and signals the difference between the expected value of rewards, and the value of rewards actually received, which is obtained through the integration of reward attributes such as the type, amount, probability and delay. It has inspired theoretical models of how certain forms of mental pathology may emerge in relation to **dopamine** function. Such pathology is frequently related to disturbed inferences leading to altered internal models of the environment. * **Dopamine** neurons show rapid responses to physically salient stimuli, which may be inherently rewarding due to their unexpected and new information value * Novelty, a specific type of salient stimulus, can evoke **dopamine** release. **Dopamine** neurons respond to novelty, but the responses habituate once the stimuli become familiar. Novelty may motivate exploration and potentially lead to higher rewards, indicating **dopamine's** role in signaling and processing novelty * Surprise salience, denoting the unexpectedness of a fully processed stimulus, operates at a cognitive level. This cognitive surprise can indicate the degree to which an outcome is unexpected, controlling the learning rate. **Dopamine** responses to surprise can modulate learning and are crucial for adapting to unexpected outcomes * Altered **dopamine** function, implicated in diseases like schizophrenia, is linked to an aberration in salience processing. Irrelevant stimuli are attributed with erroneous significance, contributing to psychotic symptoms * By altering the perception of salient stimuli, novelty, surprise, and motivational salience, this can influence **dopamine** signaling * **Dopamine** guides learning about reward outcomes, by keeping track of violations in our expectations, called prediction errors (PEs) * These errors effectively allow us to predict which outcomes are likely to be available at a particular time, and to guide our choices toward optimal behaviors. * Reward PEs (RPEs) differ from sensory and motor PEs in that as well as engendering surprise (referred to as unsigned PEs), they indicate whether outcomes were better or worse than expected, resulting in positively and negatively signed PEs * Primary rewards, including food, drink, and sex, are innately valuable due to their intrinsic survival properties. By contrast, indirect rewards such as money, derive their positive value from their association (conditioned reinforcement) with pleasurable outcomes. Primary and secondary rewards are associated with similar behaviors (e.g., choices) and **dopamine** responses, compatible with the idea that the brain transforms all rewards onto a single scale of value that facilitates decision making when different actions may procure different types of rewards * RPE signaling is primarily facilitated by the mesolimbic pathway, which transmits **dopamine** from the VTA to the nucleus accumbens (NA) in the ventral striatum. By contrast, the nigrostriatal pathway, which connects the SNc to the dorsolateral striatum, and the premotor/motor cortex is thought to facilitate action-selection of the most rewarding action Your thoughts?