Orma Ravindranath, Ashley C Parr, Maria I Perica, Samuel Elliott, Beatriz Luna
Abstract
Adolescence is generally defined as beginning at the onset of puberty, and ending when adult independence is reached. The adolescent period reflects a time of peak sensation seeking, which supports information seeking and exploration that is necessary to gain new experiences required to support the transition to adulthood. Although adaptive, sensation seeking can also lead to risk-taking behavior, contributing to an increased risk for deleterious activities such as delinquency, substance use, and reckless driving. Adolescence is also a time of heightened vulnerability to the emergence of psychopathology, including mood disorders, substance use disorders, and psychosis. Thus, the significant developmental potential and risk during this period underscores the importance of understanding the neurobiological mechanisms supporting normative adolescent brain and behavioral development.
During adolescence, affective processes, including reward and emotion, have a disproportionate effect on behavior relative to cognitive processes which, according to Dual Systems models, reflects differing developmental trajectories of these systems. Behavioral findings indicate that adolescents can access many cognitive processes, such as inhibitory control, at adult-like levels in certain contexts (i.e., when offered rewards), but their cognitive processes are inconsistent and unreliable. Studies have also found that adolescents are more sensitive to rewards and are still developing the ability to process and regulate emotions. These behavioral changes are supported by changes in functional brain activation and connectivity across affective and cognitive networks. Additionally, it has been suggested that adolescence may be a critical period of plasticity for prefrontal cortical development, during which experience interacts with neurobiological factors to affect normative brain development. This critical period is likely initiated and maintained by neurobiological processes that support adolescent development in general, including large-scale changes in GABA, glutamate, and dopamine neurotransmitter systems. Cortical gray matter decreases across childhood, adolescence, and into early adulthood, believed to reflect synaptic pruning mechanisms of brain specialization, while white matter volume increases across this period to facilitate greater communication across brain regions. Furthermore, the myelination of these white matter tracts increases through adolescence and young adulthood, allowing for more effective signaling and contributing to the closing of the adolescent critical period.
Taken as a whole, the current literature suggests that the adolescent period encompasses key development of neurobiological and cognitive processes. These critical maturational processes, coupled with the increased risk of psychiatric disorders and life-threatening behaviors, highlight the importance of understanding normative adolescent neurocognitive development, its underlying mechanisms, and how these processes can go awry. Further research will seek to expand on our current knowledge of brain maturation and its mechanisms in order to improve mental health and cognitive outcomes during adolescence and into adulthood.