The contribution of neuroscience
There is now a significant body of research that explores the neurobiological and neuropsychological underpinnings of young people’s developmental experience.
This research confirms that the distinction between teenagers and adults is more than one of age. It provides for a more complex, affirmative explanation of young people’s developmental experience to replace the long held assumption that adolescents are inherently troubled and lacking in rationality and self restraint.
David Dobbs from National Geographic (see attached) writes that the adolescent is an “…exquisitely sensitive, highly adaptable creature wired almost perfectly for the job of moving from the safety of home into the complicated world outside”.
Neuroscience has the potential to reveal more about of how social learning and experience interacts with the physiology of brain processes so that a realistic appraisal of each young person’s capacity to cope with developmental challenges can be made. This will allow parents, teachers and health professionals to better understand and respond to the developmental needs of the young people in their care and form realistic expectations for them that are challenging without being overwhelming.
How does the brain develop during adolescence?
In the late 20th century, researchers developed brain-imaging technology that enabled the physical development and patterns of activity of the adolescent brain to be tracked. It emerged that as young people move through adolescence, their brains undergo extensive remodeling that is only completed until their mid-20s.
Physical changes move in a slow wave from the brain's rear to its front, from areas close to the brain stem that look after older and more behaviorally basic functions, such as vision, movement, and fundamental processing, to the evolutionarily newer and more complicated thinking areas up front.
Myelination & Pruning: 2 crucial physiological processes
Myelination is a process through which a fatty substance called myelin (the brain's white matter) envelops and insulates the brain's axons (the long nerve fibers that neurons use to send signals to other neurons). This boosts the transmission speed of axons. At the same time the dendrites (the branch like extensions at the end of each axon that receive signals from other axons) grow twiggier. The most heavily used synapses (the chemical junctures across which axons and dendrites send messages) grow richer and stronger. All this serves to stabilize the neural networks that are critical to the brain’s operation and makes them more efficient.
At the same time, the brain's cortex (the outer layer of gray matter where we do much of our conscious and complicated thinking) becomes thinner but more efficient through a process called synaptic pruning. This involves withering of the neural networks that are less used.
These changes evolve the brain into an organ more functional for coping with life as an adult but this comes with a decrease in the brain’s flexibility and adaptability.
The brain areas of most significance in adolescent development
The pre-fontal cortex – executive functions
The prefrontal cortex is the brain region most closely associated with the executive functions and the regulation of behaviour. The brain’s executive functions enable people to:
- Focus, organise and prioritise
- Link actions to logical consequences
- Control impulses, regulate emotions and moderate behaviour
- Balancing short term rewards with long-term goals (motivation)
The brain’s frontal areas, including the pre-frontal cortex are restructured in the teenage years but are not fully developed until the early to mid-twenties (Shonkoff & Phillips, 2000; Giedd, Blumenthal, & Jeffries, 1999)
Ventral striatum - reward based decision making
The ventral striatum is a reward centre in the brain where much adolescent brain functioning takes place. It is where decisions are made based on rewards and emotions without the back-up cognitive strength of the pre-frontal cortex. The ventral striatum plays a major role in reward-motivated behavior and is closely associated with the tendency of young people to engage more that adults in sensation seeking and risk taking behavior that is often viewed as impulsive and instinctive.
The corpus callosum - integrating logic and creativity
The corpus callosum connects the brain's left and right hemispheres and carries traffic essential to many advanced brain functions. During adolescence it steadily thickens and stronger links also develop between the hippocampus (a sort of memory directory) and frontal areas that set goals and weigh different agendas. As the corpus callosum develops young people get better at integrating memory and experience into decisions and become more self aware. Like the prefrontal cortex, it reaches full maturity in the mid-twenties.