Article of the Month | June 2021
Teens’ Tendency to Take Risks Exposed by their Brain’s Viscoelasticity
by Dr. Dimitria Bonizol Camasao
Senior Application Specialist, Rheolution Inc.
Is there anything you remember doing when you were younger that you would never do again? We usually say that children and adolescents are not aware of all the risks involved in an activity so it is easier for them to not hesitate. This is definitely a reasonable statement. But there is something else happening in our brain that can be related to this change when it comes to risk-taking decisions.
A research group from the University of Delaware led by Prof. Curtis L. Johnson investigated if physiological differences in the maturation of key brain regions could explain the heightened risk-taking tendencies during adolescence. In the article entitled “Viscoelasticity of reward and control systems in adolescent risk taking” published in the Neuroimage Journal, the authors mentioned that risk-taking behaviors were suggested to be controlled by two counterbalancing brain systems: the reward-system, also referred to as the socioemotional system, and the cognitive control system, which is responsible for regulating impulse responses. Since the first starts to develop first chronologically, this developmental imbalance potentially makes adolescents more susceptible to engaging in risky activities.
Tissue development and its stiffness
Human tissues develop progressively during childhood and adolescence, and the stiffness reflects their composition and arrangement. In particular, the relative increase of brain components such as myelin, extracellular matrix proteins and brain cells can contribute to tissue stiffening. The authors considered stiffness and brain viscoelasticity as an indicator of the integrity and development of the brain region. The group hypothesized that the difference in stiffness between the socioemotional and cognitive brain systems during adolescence reflects their level of maturation and consequently the high risk-taking tendencies.
Magnetic resonance elastography
To evaluate the stiffness of these brain regions, a technique known as magnetic resonance elastography (MRE) was used in this study. MRE evaluates the propagation of mechanical waves applied in the tissue with a magnetic resonance imaging (MRI) technique. The processing of the images generates elastograms which are quantitative maps of tissue stiffness. This technique is already used in clinical practice to detect the presence of liver fibrosis related to the formation of large amounts of scar tissue that can compromise organ function. In addition, health professionals and scientists are exploring applications in other diseases such as Alzheimer’s, heart failure and breast cancer.
The study recruited 44 adolescents (22/22 male/female from 12 to 14 years old) to participate in the MRE technique and in a risk-taking assessment study that included the Balloon Analogue Risk Task (BART) and the yellow light task (YLG). These two assessment tasks provide a model for the unpredictable rewards that exemplify real-world risky behaviors. The regions of the brain evaluated by MRE were the nucleus accumbens (NAcc) related to the reward system, and the ventromedial prefrontal cortex (vmPFC) and the orbitofrontal cortex (OFC), both related to the self-regulatory behavior.
The results showed a mean stiffness of 2.94 kPa for the NAcc (reward system), 2.75 kPa for the OFC, and 2.97 kPa for the vmPFC (both self-regulatory). These values individually did not show a significant correlation with risk taking behavior. Instead, the difference in stiffness between the socioemotional and cognitive brain regions significantly correlated with risk-taking tendencies evaluated by both the YLG and BART. These results suggested that a more developed socioemotional region or a more developed cognitive center among the participants are not mediators of risk, but the higher imbalance between these regions did correlate with higher risk-taking tendencies. This imbalance is more pronounced at early years of life and so, this can explain your answer to the first question of this publication.
In most cases, brain activity measured by functional magnetic resonance imaging (MRI) is used to study risk-taking tendencies. This study is one of a few articles that reported a correlation between tissue structure and human behavior. The authors believe that analyzing the brain structure through its stiffness can provide a more complete understanding of how physiology affects behavior. In addition, this technique could be used as an indicator of those adolescents who are more prone to real world risky activities and a useful measure for characterizing response to intervention.
 McIlvain, G., Clements, R. G., Magoon, E. M., Spielberg, J. M., Telzer, E. H., & Johnson, C. L. (2020). Viscoelasticity of reward and control systems in adolescent risk taking. NeuroImage, 215, 116850.