More Clues Found in Mystery of Adolescent Brain

(March 18) -- Any parent or middle-school teacher could tell you that adolescents often have, shall we say, a resistance to learning. In fact, behavioral scientists have shown that certain cognitive processes slow down through puberty. In video game tests of spatial learning, for example, middle-schoolers did not perform nearly as well as fifth-graders.

But now scientists say they have pinpointed the neurological mechanism that most likely clouds the adolescent brain, along with a possible trick for spurring those 'tween and teen neurons to start firing again.

In the latest issue of the journal Science, physiologist Sheryl Smith and her colleagues at the State University of New York's Downstate Medical Center describe a chemical receptor that becomes more prevalent during the pubescent years and limits certain kinds of learning. The group also identifies a stress hormone that can counteract these effects, dispersing the cloud from the teenage brain.

"The brain has excitatory forces and inhibitory forces," Smith told AOL News. "The nerve cells in the brain communicate by being activated and being excitable, but there are ways of quieting down brain cells."

The problem is that slowing this activity can have negative effects. "If there's too much inhibition in your brain," Smith explained, "you're not going to be able to learn."

A brain chemical known as GABA, which acts through sites called receptors, can increase inhibition. Smith likens the brain's GABA receptors to the brakes on a car. Those brakes are generally slammed during puberty.

Smith and her group found increases in these receptors during puberty, and they also noticed the presence of an unusual kind of receptor that isn't present prior to this stage and can be hard to find in adults too. In their experiment, they attempted to teach mice a specific task and found a marked difference between age groups. The pre-pubescent mice performed well, but the pubescent subjects did not. "They didn't learn at all," Smith said.

To test their theory that these strange receptors were to blame, they also tested mice that were genetically engineered to lack them. These mice performed beautifully. "That suggested that at puberty, this new kind of GABA receptor which suddenly appears is impairing learning," Smith said.

The good news? They also identified a stress hormone that puts the clamps on this anti-learning receptor. Injecting the slow-to-learn mice with this hormone reversed the effects, enabling them to recover and learn as well as their pre-pubescent counterparts did.

Smith cautioned that this phenomenon doesn't affect all kinds of learning, and the effect also varies among kids. Some have no trouble learning at all. As a parent, though, she has thought about how to put these findings into practice. "I don't want the message to be that stress is good," Smith said. "Too much stress is always bad."

Smith said the mild stress induced by the occasional parental nudge could counteract those receptors, but ultimately the child is the strongest force. "The best way to do it is to create a situation where they're internally motivated," she said. "If they put the stress on themselves, it's the appropriate level."