FIGURE 2-1 Profiles of parameters of human brain development and the estimated age ranges for research animal models. This figure illustrates the timing of changes in the number of brain synapses, cerebral blood flow, and metabolism (blue) and in brain myelination (green). The colored bars below the figure reflect the approximated human age equivalent of the rat (blue) and pig (green) based on species specific developmental profiles.
SOURCE: Adapted from Casey et al., 2005.
tional organization of the brain reflect a dynamic interplay of progressive and regressive events that occur simultaneously as the developing individual interacts with the environment. Although total brain size is about 90 percent of adult size by age 6 years, the brain continues to undergo dynamic changes throughout adolescence and into young adulthood (Yakovlev and Lecours, 1967). Current neuroimaging methods do not have the resolution to delineate the processes that underlie the observed developmental changes beyond observations of the brain’s gray and white matter subcomponents. The techniques do, however, allow for assessment of functional sequelae of concussions and, together with animal models, suggest that the developing brain responds differently to concussion than does the mature brain (Choe et al., 2012; Shrey et al., 2011).