The Brain's Happy Signal

For me, one of the most exciting findings was published early in 2009. It showed a happy signal activated in the brain.

This image is drawn based on the article, Altered striatal activation predicting real-world positive affect in adolescent major depressive disorder, by Forbes EE, Hariri AR, Martin SL, Silk JS, Moyles DL, Fisher PM, Brown SM, Ryan ND, Birmaher B, Axelson DA, Dahl RE, in the American Journal of Psychiatry. 2009 Jan;166(1):64-73. The scientists developed a game in which teenagers could win money while their heads were in the functional MRI scanner. The functional MRI scan detects which parts of the brain are energized and active based on the increased flow of oxygenated blood to the area of activity.

Teenagers who were depressed and matched teenagers who did not have depression were scanned at the moment they were told that they won. The teenagers who did not have depression showed activation in the caudate nucleus, shown in yellow and orange in the image. The teenagers who had depression had cortical activity reflecting thought, but no activation in the caudate. Thus, the yellow and orange in the image depicts a happy signal.

A similar finding was in a previous article, Reward, motivation, and emotion systems associated with early-stage intense romantic love, by Aron A, Fisher H, Mashek DJ, Strong G, Li H, Brown LL, in the Journal of Neurophysiology. 2005 Jul;94(1):327-37. When young adults who were in love were shown photos of their loved once, their scans showed activation in the ventral tegmental area, shown in red, and in the caudate. Brain cells in the ventral tegmental area send connections to the caudate.

This changed what I thought about depression. I used to think that depression involved excessive stress and negativity in life. But this showed that depression involves not having sufficient happy signals to balance out stress and negativity. This implies that to avoid depression and maintain a reasonably happy life, it is important to always make sure that there are enough positive activities to generate enough happy signals to balance out the signals of stress and dealing with negative events.

The two articles showed activation of the “reward circuit” (which I call “happy signals”) from winning a game and from seeing a beloved one. There are many other ways to activate happy signals in the brain, including, joking with friends, giving and receiving positive feedback, solving a problem, eating an amazing meal. Nerdy people get happy signals by learning something interesting or engaging in their own nerdy activities. There is even a quiet calming joy in doing an Obsessive-Compulsive activities such as organizing.

Although the research so far implies that happiness involves activity in the caudate, it seems to me that different kinds of happiness can have distinctly different feelings. Eating vanilla ice cream and chocolate ice cream are different experiences, but the both are ice cream. Happiness has different flavors as well.  The elation of love feels a little different from the excitement of a nerdy discovery, which is different yet from the thrill of watching home team win, yet all are happy feelings.

Other feelings don't appear to have different flavors. Anxiety and anger can be of different degrees and intensities, but anxiety or anger from one stress does not feel different from another stress.  Sadness, too, can be of different intensities, but there appears to be two versions, an agitated sadness with crying, and a low energy depression where it is difficult to accomplish tasks.

Copyright 2010, Henry A. Doenlen, M.D. All rights reserved.