Two types of dopamine neuron distinctly convey positive and negative motivational signals

Dopamine neuron complexity Dopamine neurons at the base of the brain are crucial for normal motor behaviour, and their loss leads to conditions such as Parkinson's disease. Yet the activity of dopamine neurons is not related to body movements, but to reward events. Recent theories suggest that dopamine neurons, as a homogeneous functional group, guide motor learning via reward-related signals. Now a study in monkeys undergoing Pavlovian conditioning to 'positive' and 'negative' stimuli shows that dopamine neurons are more heterogeneous than this model implies. Different groups of dopamine neurons, located in slightly different areas of the brain, have specific responses to pleasant and unpleasant stimuli, as well as to the trigger stimuli associated with these events. This suggests that dopamine neurons have a more complex involvement in learning control, encoding more subtle signals than simple reward.