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.