It was posited that the effects of susceptibility genes would be more penetrant, ie, “closer to the gene,” at the level of biologically based neuroimaging intermediate phenotypes rather than at the level of a complex and phenotypically heterogeneous psychiatric syndrome.4 Neuroimaging intermediate phenotypes, akin to cognitive or electrophysiological intermediate phenotypes, could therefore be used to enhance the potential to link genetic
variation to a complex psychiatric disorder, such as schizophrenia. Hundreds Inhibitors,research,lifescience,medical of published articles have ensued, describing studies to investigate the association of genetic variation with brain activity as pertinent to schizophrenia and other CNS disorders. We currently review Inhibitors,research,lifescience,medical several critical trends in the evolution of the field of imaging genetics as applied to schizophrenia LY2157299 datasheet research. We then discuss where we are poised to go next: innovations in imaging analysis and genetics analysis, effective connectivity modeling, and polygenic risk models are on the peak of the next wave of imaging genetics. The neuroimaging intermediate phenotype The neuroimaging intermediate phenotype is conceptually analogous to an intermediate phenotype for
common complex medical disorders. Inhibitors,research,lifescience,medical It is logical to assume that genes would show stronger associations with the biological substrates contributing to risk of a disorder, with measurable quantitative traits along a pathophysiologic causal pathway, intermediate to the end complex
syndrome. Intermediate phenotypes in other realms of medicine include lipid level as an intermediate phenotype for Inhibitors,research,lifescience,medical heart disease, sodium homeostasis as an intermediate phenotype for hypertension, and body mass index as an intermediate phenotype for diabetes.5,6 We favor the term “intermediate phenotype” over the more popular term “endophenotype,” though the Inhibitors,research,lifescience,medical two terms are essentially interchangeable. The term “endophenotype” (which was introduced into psychiatric genetics in the 1970s7) initially referred to a trait that is “internal” that may be discoverable by a “biochemical test or microscopic examination,” but is not external or overtlymanifest. Also, the term “endophenotype” does not emphasize the concept of intermediacy in pathogenicity. Criteria for the establishment of a neuroimaging-based intermediate medroxyprogesterone phenotype for schizophrenia, as in other fields of medicine, are that the intermediate phenotype: (i) is heritable; (ii) is found with increased frequency in healthy relatives of ill probands; (iii) exists temporally before the onset of the clinical illness in the pathophysiological pathway to the emergence of the clinical syndrome. As expounded in a review by Tan et al, evidence for each of these criteria has accumulated for the syndrome of schizophrenia, with cognitive dysfunction often integral and assayable at the brain level by task-based neuroimaging intermediate phenotypes.