Changes in cerebral functional organization during cognitive development
Introduction
A fundamental goal of developmental cognitive neuroscience is to understand how age-related changes in the anatomy and physiology of the brain are linked to the maturation of cognitive abilities. It is well established that brain development and cognitive maturation occur concurrently during childhood and adolescence [1, 2, 3], but much less is known about the direct relationship between neural and cognitive development. Here, we review the available evidence linking patterns of change in neuroanatomy and neurophysiology to development in cognitive ability during childhood and adolescence.
This review is timely as neuroimaging tools, such as functional magnetic resonance imaging (fMRI), were first used to address developmental questions only a decade ago [4]. Measures of brain anatomy and connectivity, together with fMRI, are important tools in clarifying changes that occur in the brain during development. So, what has been learned about the biological substrates of cognitive development? What impact have studies had on our understanding of the biology of developmental disabilities and effective interventions? Finally, which directions is the field of developmental cognitive neuroscience currently moving towards?
Section snippets
Magnetic resonance imaging technologies measure brain development
Magnetic resonance imaging (MRI) technologies have introduced a new set of tools for capturing features of brain development in living, developing humans. MRI is particularly well suited to the study of children, as it provides exquisitely accurate anatomical images without the use of ionizing radiation [5]. This method not only permits the scanning of children's brains, but also the repeated scanning of the same individual over time, thus providing precise measurements of neuroanatomical
MRI-based anatomical studies show changes in gray and white matter
Several studies have used structural MRI to map the anatomical course of normal brain development [6]. Although total brain size is approximately 90% of its adult size by age six, the gray and white matter subcomponents of the brain continue to undergo dynamic changes throughout adolescence. Data from recent longitudinal MRI studies indicate that gray matter has an inverted U-shape pattern, with greater regional variation than white matter [18, 19••, 20, 21•]. Further, these developmental
Applications of imaging techniques to learning and intervention studies
MRI techniques are particularly well suited to tracking brain development and studying learning, as repeat scanning does not rely on ionizing radiation-based measures. Learning studies using these methods in adults show rapid training effects and changes in neural recruitment during the course of learning [45]. These studies show increasingly focal and enhanced activity in cognitive task-relevant regions, and decreased activity in task-irrelevant regions [46•], not unlike the developmental
Conclusions and future directions
Overall, the structural and functional studies reviewed here suggest that brain regions subserving primary functions, such as motor and sensory systems mature before higher-order association areas that integrate those primary functions (e.g. prefrontal cortex). In structural imaging studies, this is evidenced by cortical gray matter loss occurring earliest in primary sensorimotor areas and latest in dorsolateral prefrontal and lateral temporal regions [19••]. In functional imaging studies,
References and recommended reading
Papers of particular interest, published within the annual period of review, have been highlighted as:
• of special interest
•• of outstanding interest
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