Integrating neurodevelopmental imaging and genetic designs

Genetic influences on behaviour are complex and, as such, the effect of any single gene is likely to be modest. The focus of this paper is on integrating neuroimaging measures with genetic designs, where neuroimaging measures may serve as an intermediate phenotype in investigating the effect of single genes on human behaviour, and by extension, in neuropsychiatric disease. To qualify as a potential intermediate phenotype, these measures should meet a number of criteria, including being heritable, implicated in the disorder of interest, being stable over time, and firmly grounded in neuroscience. Furthermore, a number of other factors should be considered in investigating single gene effects to maximize the power of the investigation. Throughout the text, we briefly discuss examples to illustrate each of these points. We end by discussing a recent study of single gene effects on brain morphometric measures in attention deficit hyperactivity disorder (ADHD) to illustrate a number of these points in more detail.