It will also be important to begin to look more closely at how the interactions between brain regions are affected by genetic and environmental factors. Behaviors arise from the interactions of many different brain regions, and a variety of neuropsychiatric disorders have demonstrated the presence of impaired functional or structural connections between brain regions (Friston, 2005; Minshew & Williams, 2007; Rich et al., 2008). Studies have found measures of brain connectivity such as EEG coherence to be highly heritable (van Beijsterveldt, Molenaar, de Geus, & Boomsma, 1998) and to show developmental changes (Thatcher, North, & Biver, 2007; van Baal, Boomsma, & de Geus, 2001). Resting state fMRI studies have also found increased correlations between activity in different brain regions with maturation (Fair et al., 2008). In a previous study of a subset of this population, we found that variance decreased and strength of intracortical correlations increased in several of the same association areas that demonstrate increasing heritability in the current study (Lerch et al., 2006). It is tempting to speculate that increasing heritability in these late-developing regions may be also be related to the increasing functional integration of these areas in maturing cortical networks.
