Mismatch Negativity as a Psychophysiological Index of Cognitive Function in Schizophrenia

It is now widely accepted that cognitive deficits, beyond other psychiatric symptoms (e.g., delusion, hallucination, emotional flattening, social withdrawal and apathy), is far most relevant to social functional outcome in schizophrenia. Accordingly, the treatment target has been shifted to the area, developing new drugs that facilitate cognitive function and building up new psychosocial rehabilitation programs that directly approach the cognitive deficits. Despite the desirability to target these deficits, no standard neuropsychological test batteries exist for assessing the level of cognitive function. Mismatch negativity (MMN), an auditory event-related potential component, is a measure of preattentive information processing and its amplitude has repeatedly been demonstrated to be reduced in schizophrenia. MMN deficits are a robust feature in chronic schizophrenia and indicate abnormalities in automatic context-dependent auditory information processing and auditory sensory memory in schizophrenia. Moreover, the deficits have been related to poor social functioning level and social skills acquisition, hypofunction of NMDA system, and illness duration, which indicate the validity of accepting MMN as a biomarker of the disease. In this article, we present a summary of the discussions about the plausibility of MMN to be used as a neurobiological index for assessing the cognitive function and also its predictability of social functional outcome in schizophrenia.