Dopamine

What is dopamine?

Dopamine is a neurotransmitter, a chemical messenger involved in movement, motivation, reward-related learning, and other functions. The body makes it from the amino acid tyrosine. What dopamine does depends on the pathway and the cells receiving the signal.

Wanting and liking

Dopamine helps explain why we pursue rewards, but wanting a reward and enjoying it are different processes. Berridge and Robinson’s research draws out this distinction. Calling dopamine the pleasure chemical misses it.

Motivation and learning can contribute to compulsive reward seeking. Addiction, however, involves multiple biological and environmental factors. A dopamine response by itself does not tell you that an activity is addictive.

Dopamine and reward-prediction errors

One important research finding concerns the difference between an expected reward and what actually occurs. In the monkey experiments discussed by Schultz, Dayan, and Montague (1997), an unexpected juice reward produced a brief increase in activity in recorded dopamine neurons. After learning that a cue predicted the juice, the brief response shifted to the cue. If the expected juice was omitted, activity fell around the time it should have arrived.

The authors interpreted this pattern as a reward-prediction-error signal: information about whether an outcome was better or worse than expected, which can help update learning. A smaller response to fully predicted juice does not mean the animal no longer enjoys it. This account concerns particular reward-learning signals, not every dopamine neuron or every way a memory forms.

Movement and other functions

Dopamine also helps regulate movement through circuits involving the basal ganglia. Disruption of these pathways is important in Parkinson’s disease, which can involve tremor, rigidity, and slow movement.

Researchers study dopamine signaling in mood, learning, and several psychiatric conditions as well. There is no single global dopamine level that explains all of these functions or disorders.

Why it matters

Invoking dopamine can make an explanation sound scientific without making it informative. To explain a behavior, you still need to identify the process involved and what the evidence shows.