Dysfunctional connectivity in schizophrenia.

Our understanding of brain function has developed considerably since the advent of cognitive neuroscience and functional neuroimaging. Apparently, there are two central principles that functional brain architectures conform to: functional specialisation and functional integration. The former posits that brain systems are specialised for various perceptual and cognitive functions, and the latter emphasises interactions among these specialised systems. This integration is mediated by the functional equivalent of anatomical connections, i.e. effective connectivity (defined as the influence one neuronal system exerts over another). The notion of effective connectivity engendered the disconnection hypothesis, which represented an attempt to understand schizophrenia in mechanistic terms. This paper reviews the disconnection hypothesis and its implications for how one might use the powerful tools that are emerging from functional neuroimaging and genomics, to pinpoint the mechanisms that might cause schizophrenia.