In the MRI study, James Bjork, Ph.D., and others in the laboratory of Daniel Hommer, M.D., scanned the brains of twelve adolescents aged 12 to 17 years and twelve young adults aged 22 to 28 years. While being scanned, the subjects participated in a game-like scenario risking monetary gain or loss. The participants responded to targets on a screen by pressing a button to win or avoid losing 20 cents, $1, or $5.
For both age groups, the researchers found that the anticipation of potential gain activated portions of the ventral striatum, right insula, dorsal thalamus, and dorsal midbrain, with the magnitude of ventral striatum activation sensitive to gain amount. In adolescents, however, the researchers found lower activation of the right ventral striatum centered in the nucleus accumbens, a region at the base of the brain shown by earlier research (see Alcohol Researchers Localize Brain Region That Anticipates Reward August 3, 2001 at News Releases-http://www.niaaa.nih.gov) to be crucial for motivating behavior toward the prospect of rewards.
"Our observations help to resolve a longstanding debate among researchers about whether adolescents experience enhanced reward from risky behaviors--or seek out alcohol and other stimuli because they require enhanced stimulation. They also may help to explain why so many young people have difficulty achieving long-term goals," according to James Bjork, Ph.D., first author on the study.
When the researchers examined brain activity following gain outcomes, they saw that in both adolescents and young adults monetary gain similarly activated a region of the mesial frontal cortex. "These results suggest that adolescents selectively show reduced recruitment of motivational but not consummatory components of reward-directed behavior," state the authors.
In a nutshell: adolescents want stuff but they are too lazy to work to get as much as they want. Worse yet, they have few skills with which to work to get what they want. No wonder they frustrated, depressed, and angry.
The mentioned earlier research is here: Alcohol Researchers Localize Brain Region That Anticipates Reward
Researchers in the laboratory of Daniel Hommer, M.D., measured changes in blood oxygen level dependent contrast in a functional magnetic resonance (FMRI) scanner in order to track changes in brain activity that occurred while eight volunteers participated in a videogame task involving real money. In this monetary incentive delay (MID) task, participants saw cues that indicated that they might win or lose money, waited for a variable anticipatory delay period, then tried to either win or avoid losing money by pressing a button in response to a rapidly presented target. The researchers examined the response of the nucleus accumbens during anticipation of different amounts of potential rewards (i.e., gains of $0.20, $1.00, and $5.00) or punishments (i.e., losses of $0.20, $1.00, and $5.00). They found that nucleus accumbens activity increased as volunteers anticipated increasing monetary rewards but not punishments. Another nearby brain region, the medial caudate, showed increased activity not only during anticipation of increasing rewards but also during anticipation of increasing punishments.
Imagine a drug or gene therapy that stimulates the growth or activity of the nucleus accumbens. It might make adolescents and even adults more motivated. The educational and economic effects of such therapies could be enormous.
By contrast, stimulation of growth of the appropriate portion of the medial caudate might be more useful for treating criminals. If criminals could be made to have a greater fear of punishment they might become less likely to violate the law. I'm betting that most criminals will eventually be found by brain scan studies to have a lower fear of punishment than the population as a whole.
For more on young brains see my previous posts Adolescence Is Tough On The Brain and Adolescent Mice More Sensitive To Addictive Drugs and Early Nicotine Exposure Increases Nicotine Craving.
|Share |||Randall Parker, 2004 February 25 11:06 AM Brain Development|