Figure 1.

Illustration of proposed changes in tonic versus phasic dopamine signaling through adolescence. Tonic signals increase, reflecting increases in incentive motivation and enabling approach toward incentive contexts. As discussed in the text, phasic signals must be increasingly strong to be discriminated against the background tonic level. In adulthood, tonic levels return to the intraindividual baseline, and weaker phasic signals are able to influence reward-related learning.