### abstract ###
The mature human brain is organized into a collection of specialized functional networks that flexibly interact to support various cognitive functions.
Studies of development often attempt to identify the organizing principles that guide the maturation of these functional networks.
In this report, we combine resting state functional connectivity MRI, graph analysis, community detection, and spring-embedding visualization techniques to analyze four separate networks defined in earlier studies.
As we have previously reported, we find, across development, a trend toward segregation between regions close in anatomical space and integration between selected regions distant in space.
The generalization of these earlier trends across multiple networks suggests that this is a general developmental principle for changes in functional connectivity that would extend to large-scale graph theoretic analyses of large-scale brain networks.
Communities in children are predominantly arranged by anatomical proximity, while communities in adults predominantly reflect functional relationships, as defined from adult fMRI studies.
In sum, over development, the organization of multiple functional networks shifts from a local anatomical emphasis in children to a more distributed architecture in young adults.
We argue that this local to distributed developmental characterization has important implications for understanding the development of neural systems underlying cognition.
Further, graph metrics are similar in child and adult graphs, with both showing small-world -like properties, while community detection by modularity optimization reveals stable communities within the graphs that are clearly different between young children and young adults.
These observations suggest that early school age children and adults both have relatively efficient systems that may solve similar information processing problems in divergent ways.
### introduction ###
The mature human brain is both structurally and functionally specialized, such that discrete areas of the cerebral cortex perform distinct types of information processing.
These areas are organized into functional networks that flexibly interact to support various cognitive functions.
Studies of development often attempt to identify the organizing principles that guide the maturation of these functional networks.
CITATION CITATION .
A major portion of the work investigating the nature of functional human brain development is based on results from functional magnetic resonance imaging studies.
By examining the differences in the fMRI activation profile of a particular brain region between children, adolescents, and adults, the developmental trajectory of that region's involvement in a cognitive task can be outlined CITATION, CITATION, CITATION CITATION.
These experiments have been crucial to our current understanding of typical and atypical brain development.
In addition to fMRI activation studies, the relatively new and increasingly utilized method of resting state functional connectivity MRI allows for a complementary examination of the functional relationships between regions across development.
Resting state fcMRI is based on the discovery that spontaneous low-frequency blood oxygen level dependent signal fluctuations in sometimes distant, but functionally-related grey matter regions, show strong correlations at rest CITATION.
These low frequency BOLD fluctuations appear to relate to spontaneous neural activity CITATION CITATION.
In effect, rs-fcMRI evaluates regional interactions that occur when a subject is not performing an explicit task CITATION, CITATION, CITATION CITATION.
To date, rs-fcMRI has been used in several domains to examine systems-level organization of motor CITATION, memory CITATION, CITATION, attention CITATION, and task control systems CITATION, CITATION, CITATION .
In addition, because rs-fcMRI does not require active engagement in a behavioral task, it unburdens experimental design, subject compliance, and training demands.
Thus, rs-fcMRI is becoming a frequently used tool for examining changes in network structure in disease CITATION CITATION, in aging CITATION, CITATION, and across development CITATION, CITATION CITATION .
In previous work regarding task-level control in adults, we applied rs-fcMRI to a set of regions derived from an fMRI meta-analysis that included studies of control-demanding tasks.
This analysis revealed that brain regions exhibiting different combinations of control signals across many tasks are grouped into distinct fronto-parietal and cingulo-opercular functional networks CITATION, CITATION.
Based on functional activation profiles of these regions characterized in the previous fMRI study, the fronto-parietal network appears to act on a shorter timescale, initiating and adjusting top-down control.
In contrast, the cingulo-opercular network operates on a longer timescale providing set-initiation and stable set-maintenance for the duration of task blocks CITATION .
Along with these two task control networks CITATION, CITATION, a set of cerebellar regions showing error-related activity across tasks CITATION formed a separate cerebellar network.
In adults, the cerebellar network is functionally connected with both the fronto-parietal and cingulo-opercular networks CITATION, CITATION.
These functional connections may represent the pathways involved in task level control that provide feedback information to both control networks CITATION, CITATION .
Another functional network, and one of the most prominent sets of regions to be examined with rs-fcMRI, is the default mode network.
The default mode network was first characterized by a consistent decrease in activity during goal-directed tasks compared to baseline CITATION, CITATION.
Resting-state fcMRI analyses have repeatedly shown that these regions, along with associated medial temporal regions, are correlated at rest in adults CITATION, CITATION, CITATION, CITATION.
While the distinct function of the default mode network is often linked to internally directed mental activity CITATION, this notion continues to be debated CITATION, CITATION, CITATION CITATION .
