These results demonstrate that functionally relevant effects of genetic variation can be detected in brain structure, an important step toward supporting the validity of brain anatomy as an intermediate phenotype between genes and behavior. The regional variation of heritability is also intriguing regarding implications of the relative balance of genetic and environmental factors for specific cognitive functions. In the studies described above, primary motor and sensory cortices fell within regions shaped most strongly by environmental factors, possibly congruent with the role of these regions in adapting to the varying sensory experiences and motor activities of daily life. By contrast, regions of association cortex which integrate information from other brain regions and support higher cognitive activities such as language and executive function were those that more clearly showed effects of genetic variation.
