Aspects of Neurodevelopment in Early Adolescence

During the process of brain development there are a variety of "micro- architectural" processes that take place to create the final mature and fully functional brain. Some of these processes such as neurogenesis (birth of nerve cells) take place primarily in utero; by the time we are born, for example, the vast majority of neurons we use throughout life are present - though a number of important examples of post-natal neurogenesis are seen in key parts of the brain under a variety of conditions. The process of creating the majority of connections from neuron to neuron - synaptogenesis - occurs primarily in the first years of life; again, by the time you are five, the majority of the neural connections that underlie core functioning in all domains are in place. And again, key sculpting and synaptogenesis take place throughout life, but far fewer than in early childhood. In early adolescence, however, the key microarchitectural process involved in development is myelination. Myelination creates an "insulating" covering of the axons that span the distance from the "receptive" dendritic areas, to the cell body and then down the axon to the pre-synaptic terminal (this is a bit of an oversimplification). In essence myelination plays a major role of increasing the efficiency and speed of existing neural connections; similar to the difference between a "dial-up" (slow) and fiber optic (blazing fast) internet connection. This increased efficiency allows a quantum leap in the speed and complexity of neural network communication that appears to underlie improved cortical functioning - including the improved capacity of the cortex to modulate and regulate the lower more "impulsive" networks/areas of the brain.  The process of myelination in key areas of the cortex plays a major role in increase the "executive functioning," and cortical modulating capacity of the brain. And the balance between the reactivity of the lower and simpler regulatory areas of the brain (which can be increased by trauma) and the strength of the cortical networks that modulate these lower areas is a major determinant of self control, attention, impulse control and a variety of inter-related crucial capacities of the developing child, youth and adult. The more myelinated and mature the cortex the more capable one is of "cortical modulation" (a capacity that can be estimated with the CTA's NMT Clinical Practice Tools "Brain Map") and self-regulation - key traits in a successful person.

The fact that an adolescent does not yet have these capacities developed is a major factor that the U.S. Supreme Court is being asked to consider in these cases that are challenging the sentencing of youth to life in prison. In 2009, the U.S. Supreme Court decided these neurodevelopmental factors were crucial to their decision to declare the death penalty for adolescents unconstitutional. You can read the Amicus Brief outlining some of the key research to be considered in these cases.

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