The neurobiology of MMN and implications for schizophrenia

•MMN reduction in schizophrenia most likely arises from reduced neural synchrony of brain activity.•Decreased expression of the obligatory NR1 subunit of NMDA receptors in schizophrenia could underpin reduced neural synchrony.•Early ERP components in the middle latency range (MLR) and MMN exhibit deviance detection in healthy individuals.•Whether deviance detection in MLRs is affected in schizophrenia has not been investigated.•An unresolved issue is whether reduced MMN in schizophrenia is due to deficits in adaptation or impaired deviance detection•Use of animal models and novel methodologies are needed to advance understanding of reduced MMN in schizophrenia. Although the scientific community appears to know a lot about MMN, about its neural generators and the computational processes that underlie its generation, do we have sufficient knowledge to understand what causes the reduction of MMN amplitude in schizophrenia? Here we attempt to integrate the evidence presented in this series of papers for the special issue on MMN in schizophrenia together with evidence from other new relevant research and ask—what have we learnt? While MMN research was the purview for decades of psychophysiologists interested in event-related potentials derived from scalp recorded EEG, it is now part of mainstream neuroscience research attracting the interest of basic auditory neuroscientists, neurobiologists and computational modellers. The confluence of these developments together with increasing clinical research has certainly advanced our understanding of the causes of reduced MMN in schizophrenia as this integrative review attempts to demonstrate—but much remains to be learnt. Future advances will rely on the application of multiple methodologies and approaches in order to arrive at better understanding of the neurobiology of MMN and implications for schizophrenia.