"Functional" magnetic resonance imaging detects regions in the brain where extra oxygen in the blood flows in response to events in the environment. This is thought to represent compensation or replenishment of neurons in brain areas that have used energy to perform their roles. The diagrams above show a slice of the brain that includes a region called the ventral striatum, known to be involved in motivating organisms to seek natural (such as food and sex) and artificial (such as street drugs) rewards.

The colors indicate where extra oxygen flow occurred after research volunteers saw a signal indicating that they could win cash and while they anticipated pressing a button to win the money. In young adults (part A), both sides of the ventral striatum were robustly activated by the prospect of responding to win a reward. In adolescents (part B), however, the ventral striatum showed less activation.

Brain activity in response to learning that money had been won, however, did not differ between the two age groups. This suggests that adolescents "like" obtaining the money as much as adults do but that adolescent brains are less energized to prepare and respond to obtain it.

This illustration is from NIAAA's Laboratory of Clinical Studies, Section of Brain Electrophysiology and Imaging.

Prepared: February 2004