Risky Teenage Behavior Linked to Imbalanced Brain Activity

Imbalanced activity between OFC and NAC brain regions reduces impulse control.

Posted Oct 20, 2016

Mooshny/Shutterstock
Source: Mooshny/Shutterstock

A new study from Dartmouth College identifies a causal relationship between behavioral impulse control and an imbalance in brain function between the orbitofrontal cortex (OFC) and nucleus accumbens (NAC). The imbalance between these brain regions typically peaks during adolescence. The October 2016 findings appear in the journal Current Biology.

Wikimedia Commons/Public Domain
Orbitofrontal cortex (OFC) in green. 
Source: Wikimedia Commons/Public Domain

The orbitofrontal cortex (OFC) is a multi-faceted brain region that is involved in executive control and behavioral inhibition. The nucleus accumbens (NAC) plays a central role in reward-seeking behaviors and addiction.

The Dartmouth researchers discovered that functional imbalances between the OFC and NAC during adolescence disrupt impulse control by studying lab rats. This is the first time neuroscientists have pinpointed a causal link between behavioral inhibition and an imbalance between these two specific brain regions. 

Previous research has found that both human and non-human adolescent animals are neurobiologically hardwired to engage in risk-taking behavior. We all know from life experience that teenagers tend to have more trouble inhibiting reckless behavior than their pre-adolescent counterparts and adults.

From an evolutionary psychology perspective, the life experience that comes from novelty seeking and exploring uncharted territories is an important part of growing up. A fundamental aspect of becoming independent from one’s parents are the rites of passage and enriched life experiences teenagers have during adolescence.

Being a timid shrinking violet—who doesn't take risks and strictly adheres to the status quo—during adolescence makes it difficult to expand your horizons and can stunt your personal growth. Helicopter parenting (and being overly sheltered) sabotages teenagers' odds of evolving into well-rounded young adults who have resilience and chutzpah. 

Obviously, risk-taking behavior can be dangerous. The recklessness of adolescence and lack of impulse control often involves drug use, binge drinking, promiscuity, unsafe sex, reckless driving, playing hookie, flunking out of school, etc. But, there are many ways (such as sports) in which teenage girls and boys can take risks and push physical and psychological boundaries while fortifying self-control.

Low OFC Activity + High NAC Activity = Lack of Behavioral Inhibition

Geoff B Hall/Wikimedia Commons
Nucleus accumbens (NAC) in red. 
Source: Geoff B Hall/Wikimedia Commons

Prior to this new study, researchers in David J. Bucci's Neurobiology of Learning and Memory Laboratory at Dartmouth College had an inkling that low activity in the OFC combined with high activity in the NAC marked a specific imbalance that was linked to behavioral inhibition during adolescence. 

To test this causal imbalance between the OFC and NAC, Heidi C. Meyer, a graduate student working in Bucci's lab, used a chemogenetic approach on rats that simultaneously altered levels of activity in the OFC and NAC brain regions to mirror the imbalance that occurs during human adolescence.  

The chemogenetic technique enables researchers to "remotely control" the activity of brain cells by temporarily turning neurons in a particular brain region on or off for a short period of time.

Adult rats normally have balanced activity between the OFC and NAC. However, Meyer found that decreasing the levels of activity in the OFC and simultaneously increasing activity in NAC made it almost possible for adult rats to practice behavioral inhibition. 

The difficulty these adult rats had learning inhibitory responses matched the delay that the researchers observed in normal adolescent rats, who typically have an OFC/NAC imbalance. These findings illuminate why using executive function to exhibit self-control and behavioral inhibition is often age-dependent. The prefrontal cortex (PFC)—which houses the OFC—is not fully developed until our late teens or early 20s. 

These findings are consistent with the researchers' previous work on the brain mechanisms behind impaired inhibition during adolescence. In a statement to Dartmouth College, David J. Bucci concluded,

"Understanding how specific changes in brain function during development relate to behavior is critically important for determining why some individuals engage in excessive risk taking behavior during adolescence. Our hope is that these findings will inform new means to minimize the potential for engaging in drug use and other harmful behaviors during this important period of development."

The latest findings from Bucci et al. provide causal evidence that under activity in the OFC and overactivity in the NAC reduces behavioral control and increases risk-taking. These findings could lead to the development of targeted interventions to reduce the odds of self-harm in situations and stages of life where an individual is prone to take too much risk.

Risk-Taking Creates a Darwinian Slant Towards Survival of the Fittest

Although risk-taking can be dangerous, it's also a critical part of adolescence on a psychological and neurobiological level. Exploring uncharted territory and pushing the envelope as a teenager is how every individual finds a sweet spot between being a death-wish type of daredevil or a stick in the mud. Adolescent risk-taking is necessary to learn personalized ways to navigate life, fend for yourself, and become self-reliant.

In fact, a June 2015 study from Finland found that risk-taking behavior optimizes white matter tracts and improves the "superhighways" of connectivity between brain regions. The study concludes that taking risks improves functional connectivity and makes people smarter because they learn how to land on their feet both figuratively and literally. 

The Finnish researchers believe one reason risk-takers may become smarter is linked to the interconnection between white matter tracts, physical activity, the internal drive to seek out challenges, experience learning, and developing a sense of mastery over their environment.

This dynamic combination stimulates risk takers' brains because their daily activities often include a triad of playfulness, seriousness, and fun-loving pursuits. In a statement to SINTEF, co-author Dagfinn Moe said, 

"This finding is interesting and will be important to the way we understand the brain's development and our learning potential linked to risk-willingness. This will be useful information for parents, school teachers, sports coaches . . . All the positive brain chemicals respond under such conditions, promoting growth factors that contribute to the development of the robust neural networks that form the basis of our physical and mental skills.

The point here is that if you're going to take risks, you have to have the required skills. And these have to be learned. Sadly, many fail during this learning process—with tragic consequences. So this is why we're wording our findings with a Darwinian slant—it takes brains to take risks."

Finding a Sweet Spot that Balances NAC and OFC Activity Is Key

It's always going to be a tight-rope walk when trying to find the sweet spot between being a reckless high-risk taker with zero impulse control and a low-risk taker who completely lacks openness to experience and becomes a shut-in. 

Athletics and sports competition are always going to be a safe and constructive environment to take chances, push boundaries, and explore new territory without risking life and death. Research shows that regular physical activity can fortify your resilience and self-reliance on a neurobiological level throughout the human lifespan.

Hopefully, understanding the push-pull dynamic between the OFC and NAC will help parents, guidance counselors, and coaches pinpoint target behaviors that help adolescents achieve a healthy balance between being a reckless adrenaline junkie or falling into the trap of being a risk-averse couch potato during the teenage years.