ReviewBrain development in children and adolescents: Insights from anatomical magnetic resonance imaging
Introduction
Differences in cognition, behavior, and emotions between children, adolescents, and adults have been noted for millennia. Characterizing the neuroanatomical substrates of these differences has been more elusive. Data from animal and post-mortem studies has been able to tell us much about the basic processes underlying the development of the brain, but these types of studies are limited in what they can tell us about how individuals change over time, the extent of variability between individuals, what factors may impact that change, and the functional correlates of these differences. Magnetic resonance imaging (MRI) has opened the way for serial observations of brain changes during development in living people and thus the ability to address these questions. In this brief review we will first provide a context of the fundamental processes underlying brain formation, followed by a discussion of methodological issues in MRI. We will then summarize progress thus far on MRI studies of brain changes during development with an emphasis on the results from the longitudinal study of typically developing children and adolescents carried out by our group at National Institute of Mental Health (NIMH) over the past 15 years. We will conclude with a discussion of implications for brain–behavior relations and future directions.
Section snippets
Key events in brain development
The development of the nervous system occurs through the interaction of several synchronized processes, some of which are complete before birth, while others continue into adulthood. The first key event in the development of the central nervous system is the formation of a specialized fold of ectodermal tissue called the neural tube. The neural tube nears completion by 3–4 weeks of gestation (see Fig. 1) and is the basis for all further nervous system development. Birth defects such as spina
Methodology considerations in pediatric anatomical MRI studies
The brain is wrapped in a resilient membrane, immersed in a protective moat of fluid, and completely encased in bone. This protects the brain well from falls or attacks from predators but also creates a challenge for those interested in investigations of the organ responsible for our thinking and behavior.
Early methods of visualizing the brain in vivo, such as X-rays or computerized tomography, offered major advances but their use of ionizing radiation precluded their use in the study of
Early pediatric brain anatomical MRI studies
The first MRI studies of brain development were reported in the 1980s and focused on qualitative descriptions of gray and white matter during the first 2 years of life (Barkovich et al., 1988; Holland et al., 1986; Johnson and Bydder, 1983; Levene et al., 1982; McArdle et al., 1987). With conventional MRI sequences the gray and white matter intensities during the first 6 months are reversed from the adult pattern (i.e. gray matter appears lighter than white matter). From ages 6 to 12 months
NIMH pediatric brain imaging project
The long-term goals of the NIMH Pediatric Brain Imaging project are to (i) map the developmental trajectories of brain development; (ii) discern the genetic and environmental influences on these developmental pathways; and (iii) use knowledge of these influences to guide treatment interventions or optimize healthy brain development. Initial cross-sectional data indicated that large sample sizes or a longitudinal study design would be required to characterize the developmental changes of the
Brain–behavior relationships
A primary aim of developmental studies of brain structure is to better understand developmental changes in cognition and behavior. Although few would argue that the brain is the physical substrate for cognition and behavior, relationships between the size of a particular brain area and these functions are rarely straightforward. It is a considerable challenge to relate brain function to distributed neural networks or to the complex interactions of neurons, neurotransmitter systems, and synaptic
Conclusion and future directions
The field of pediatric structural neuroimaging has been growing rapidly in response to the realization of the complexity and potential malleability of postnatal brain development. There are now large-scale studies underway in several countries combining data from multiple sites in order to increase sample sizes and move towards the compilation of population-based measures of brain development. Advances in scanner technology are making it possible to obtain very high-resolution structural data
References (94)
- et al.
A typical trajectories of number development: a neuroconstructivist perspective
Trends in Cognitive Sciences
(2002) - et al.
Neuronal and glial cell biology
Current Opinion in Biotechnology
(2000) Age-related myelin breakdown: a developmental model of cognitive decline and Alzheimer's disease
Neurobiology of Aging
(2004)- et al.
A unified statistical approach to deformation-based morphometry
Neuroimage
(2001) - et al.
A developmental study of sex and age interactions in the human corpus callosum
Developmental Brain Research
(1992) - et al.
Cerebral MRI of human brain development—ages 4–18
Biological Psychiatry
(1995) - et al.
Relations between neuropsychological performance and brain morphological and physiological measures in monozygotic twins discordant for schizophrenia
Psychiatry Research
(1994) - et al.
Structural brain variation and general intelligence
Neuroimage
(2004) - et al.
Deformable registration of cortical structures via hybrid volumetric and surface warping
Neuroimage
(2004) - et al.
Semantic memory and the brain: structure and processes
Current Opinion in Neurobiology
(2001)