New insights on the subcortical representation of reward.

Reward information is represented by many subcortical areas and neuron types, which constitute a complex network. Its output is usually mediated by the basal ganglia where behaviors leading to rewards are disinhibited and behaviors leading to no reward are suppressed. Midbrain dopamine neurons modulate these basal ganglia neurons differentially using signals related to reward-prediction error. Recent studies suggest that other types of subcortical neurons assist, instruct, or work in parallel with dopamine neurons. Such reward-related neurons are found in the areas which have been associated with stress, pain, mood, emotion, memory, and arousal. These results suggest that reward needs to be understood in a larger framework of animal behavior.