ADC 655 Module 1 The Brain's Reward System Example

Wanting, Liking and Learning: How the Brain's Reward System Was Discovered

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Psychology and Addiction Studies Program, Aspen University

ADC 655: Neurobiology of Addiction

Instructor Name

Month Day, Year

Wanting, Liking and Learning: How the Brain's Reward System Was Discovered

Nadia, a counselor at a residential addiction treatment program in Colorado Springs, leads a weekly psychoeducation group. Both she and her program were made up for teaching. Last week a client, Marcus, asked a question she could not fully answer: "Why do I still crave meth when it doesn't even feel good anymore?" This paper reviews the science of the brain's reward system that she will draw on in her next session.

The Discovery of Reward Circuitry

Olds and Milner (1954) implanted electrodes in the brains of rats and allowed the animals to press a lever that delivered mild electrical stimulation. When electrodes were placed in certain areas, including regions along a pathway later associated with dopamine, rats pressed the lever repeatedly, sometimes thousands of times an hour, in preference to other activities. The finding showed that the brain contains circuitry whose activation is strongly reinforcing. It was quickly interpreted as the discovery of pleasure centers, a label later research would complicate.

Dopamine and Prediction Error

Schultz et al. (1997) recorded the activity of dopamine neurons in monkeys learning to associate a cue with a reward. Before learning, the neurons fired when an unexpected reward arrived. After learning, they fired when the cue appeared and no longer fired at the reward itself, which was now expected. If an expected reward failed to arrive, their activity dropped below baseline. The authors showed that this pattern matched a computational learning signal known as a prediction error: the difference between the reward expected and the reward received. Dopamine, in this view, teaches the brain which cues predict rewards and updates those predictions when outcomes differ from expectations.

Wanting Versus Liking

Berridge and Robinson (1998) reviewed evidence on what dopamine does in reward. They argued that dopamine is not necessary for liking, the pleasure of a reward: animals with dopamine depleted still showed facial reactions of pleasure to sweet tastes. Nor, they argued, is it primarily a teaching signal. Instead, they proposed that dopamine mediates incentive salience, or wanting: the attribution of motivational value to rewards and the cues that predict them, which makes them attractive and attention-grabbing. Wanting and liking usually go together, but they can separate.

Connecting to Addiction

Natural rewards, such as food, water and social contact, activate this system, which evolved to motivate behaviors that help survival. Addictive drugs activate it too, often more strongly and more directly. Repeated drug use, the later modules will show, can sensitize the wanting system to drug cues while tolerance reduces the pleasure the drug provides. The result is a person who wants a drug intensely while enjoying it less, exactly the experience Marcus described.

From Animals to People

Most of this research was done in animals, and the step to people requires care. Brain imaging in humans, discussed in later modules, has found dopamine release in response to drugs and drug cues, consistent with the animal work. But human experience involves memory, meaning, relationships and choice in ways no animal model captures. The reward system is part of the explanation for addiction, not the whole of it.

Natural Rewards and Recovery

The same system that drugs overstimulate also responds to food, exercise, music, accomplishment and connection with other people. In early recovery these natural rewards may feel flat, since the system has adapted to stronger stimulation. Over time, many people find that ordinary pleasures return. This is one reason treatment encourages building routines around activities and relationships that provide natural reward.

Why the Prediction Error Matters for Addiction

Schultz and colleagues' finding helps explain the power of drug cues. Through repeated use, cues such as a lighter, a street corner or a payday come to predict the drug, and dopamine neurons begin to fire at the cue itself. The cue then carries the motivational charge. For someone in recovery, encountering such a cue can produce a surge of wanting even when no drug is present.

Explaining It to the Group

Nadia planned to explain the science in three steps. First, the brain has a system whose job is to say "this matters, go get it," which keeps us eating, drinking and connecting with others. Second, that system is separate from the one that makes things feel good; the two usually agree but not always. Third, repeated meth use turned up the "go get it" signal for meth and its cues while the good feeling wore down, so the craving can be loud even when the high is disappointing. She would add that the system can recalibrate with time away from the drug and with other rewards, a point later sessions will develop.

What Changes With Recovery

Research suggests that some of the changes in reward signaling seen in addiction partly reverse with sustained abstinence, though the pace varies and cue-triggered wanting can persist. For clients, this means two things at once: craving may stay strong for a while after the pleasure has gone, and the balance can shift with time, new routines and other rewards.

Cautions in Translating the Science

Animal studies show mechanisms that are not always simple in people, and brain systems interact in complex ways. Nadia would avoid suggesting that clients are controlled by their dopamine, which could undermine their sense of agency. The aim is understanding, not fatalism: knowing why craving persists can make it less frightening and easier to plan for.

Conclusion

Olds and Milner revealed that the brain contains reward circuitry, Schultz, Dayan and Montague showed dopamine signaling prediction errors and Berridge and Robinson distinguished wanting from liking. Together these findings explain why people in addiction can crave a drug they no longer enjoy, and they give Nadia a clear, accurate answer for Marcus.

References

Berridge, K. C., & Robinson, T. E. (1998). What is the role of dopamine in reward: Hedonic impact, reward learning, or incentive salience? Brain Research Reviews, 28(3), 309-369. https://doi.org/10.1016/S0165-0173(98)00019-8

Olds, J., & Milner, P. (1954). Positive reinforcement produced by electrical stimulation of septal area and other regions of rat brain. Journal of Comparative and Physiological Psychology, 47(6), 419-427. https://doi.org/10.1037/h0058775

Schultz, W., Dayan, P., & Montague, P. R. (1997). A neural substrate of prediction and reward. Science, 275(5306), 1593-1599. https://doi.org/10.1126/science.275.5306.1593