On the teenage brain

Teenagers have the brain of adults, if one considers size, weight, folds and specialization in regional areas. Yet, there are some subtle but crucial neural differences that make teenagers into those strange animals we all know from Hollywood movies and personal experience.

A recent article by Kendall Powell in Nature magazine (24 August 2006) summarizes research on the neurobiology of the maturing brain that confirms some intuitive knowledge while undermining other common tales about teenagers. For example, folk psychology maintains that girls mature emotionally earlier than boys, and sure enough researchers have found that a crucial process of thinning of gray matter in the brain is completed earlier in teenage girls than boys. This process “awakes” prefrontal regions that are involved in decision making and in balancing emotional and rational inputs, providing a mechanism for the folk psychological observation.

Another interesting finding is that teenagers have a much harder time than adults at even simple tasks that involve controlling one's impulses, but with a twist. For example, when told to ignore a light visible through their peripheral vision, teenagers do as well as adults, but much larger portions of their frontal regions light up during the task. These are the regions involved in rational decisions, and apparently teenagers need to use them in overdrive to keep themselves from yielding to even very simple impulses. Imagine the extra work that teenage frontal regions have to do if the task is to keep away from sex, drugs or alcohol...

Current neurobiology also shows that, interestingly, we really ought not to give up too easily on teenagers. Contrary to the common wisdom that one can influence youngsters up to puberty, and then we simply ought to hope for the best, it turns out that the brains of even first-year college students undergo measurable changes within a span of a few months, changes that can be influenced by the educational environment to which the youngsters are exposed. This may be the last significant developmental window to help our children and students to better reason and integrate their emotional and rational circuits. So much for my many colleagues who think that teaching introductory courses to undergraduates is a waste of time (interestingly, a control group of postdoctoral students – a demographic group slightly older than graduate students – showed no such changes in the structure and activity of their brains...)

The research summarized in the Nature report also explains why people in their '50s are – on average – wiser than younger people. The brain undergoes a process of myelination (i.e., deposit of myelin, the substance that in part makes up the white matter of the brain) beginning with the teenage years. This process allows faster connections among different parts of the brain, sort of like switching from dial-up to broadband internet connection. The augmented gray matter allows an individual to recall information more quickly, and to make connections among previous experiences that better prepare her for new situations. This process of myelination has been shown to peak at around age 50, which has something to do with why middle-aged people can make use of their life experiences so much better than young people (the other reason, of course, is the 50-somethings simply have more experience, period). It seems that, indeed, youth is somewhat wasted on the young.