Disappointment may register in your brain as well as on your face.

Several areas in the brain are activated when humans and monkeys are motivated to perform a task in anticipation of a reward. When these rewards are expected, animals tend to choose an action more frequently than other alternatives. They also carry out the actions more quickly and with fewer errors.

However, in real life, rewards don't always come and we must choose an undesirable action.

The researchers set out to study the nerve circuitry involved in decision-making options set by reward bias. Their study shows that a specific area of monkeys' brains appears to be activated by disappointing results, like getting a less than expected reward for a task.

These results suggest the disappointment triggered by rewards not living up to expectations stimulates activity in yet another brain region, known as the centromedian nucleus of the thalamus. Activation of this area seems to play a complementary role, which allows animals to reach their final "action" goal when disappointment is expected.

Read WebMD's "Brain Region May Act as 'Sixth' Sense"

Disappointment Registers in the Brain

Researchers say the thalamus is associated with other brain regions that "bias" the brain to select options that will yield the biggest reward.

In the study, which appears in the current issue ofScience, researchers recorded brain activity in this region when a group of monkeys had to choose an action that would bring a smaller than anticipated reward.

They found activity in this particular area appeared to be specifically related to disappointment or unhappiness and was not activated by other stimulants. In addition, these feelings of disappointment and unhappiness interfered with the monkeys' ability to complete the task at hand.

The researchers say that this brain area participates in abolishing the bias of the large-reward action and in pursuing the requested small-reward action.

Read WebMD's "What Makes People Flinch?"

By Jennifer Warner, reviewed by Brunilda Nazario, MD

SOURCE: Minamimoto, T. Science, June 17, 2005; vol 308: pp 1798-1801.