Development of brain networks and relevance of environmental and genetic factors: A systematic review

- A review of brain network development and the influence of genetics and environment.
- Mixed findings for functional connectivity, dependent on function of network.
- DWI networks: developmental patterns for clustering, modularity and efficiency.
- CT networks: efficiency and modularity may stabilize in adolescence.
- Sparse research on genetic or environmental influence on connectivity development.

This study conducted a systematic review to synthesize findings on the development of functional and structural brain networks from the prenatal to late adolescent period. In addition, evidence for environmental and genetic influences on the development of brain networks was reviewed. Ninety two studies fulfilled the inclusion criteria. Diffusion MRI findings indicated that clustering decreases, local and global efficiency increase and modularity stabilizes or decreases with age. Structural covariance findings indicated that local efficiency, global efficiency and modularity, may stabilize in adolescence. Findings for resting-state functional MRI were mixed. Few studies have investigated genetic or environmental influences on development of structural or functional networks. For functional networks, genetic effects have been reported with few significant environmental factors. While no studies of this nature were found for structural networks, other research has provided evidence of age-related changes in heritability of white matter volume, fractional anisotropy, and cortical thickness. Further research is required to understand the development of brain networks and the relevance of environmental and genetic factors.