title: Mismatch negativity in chronic schizophrenia and first-episode schizophrenia.
abstract: BACKGROUND
  Mismatch negativity (MMN) is an event-related brain potential that is sensitive to stimulus deviation from a repetitive pattern. The MMN is thought primarily to reflect the activity of sensory memory, with, at most, moderate influences of higher-level cognitive processes, such as attention. The MMN is reported to be reduced in patients with chronic schizophrenia. However, it is unknown whether MMN is reduced in patients with first-episode schizophrenia (at first hospitalization).
  
  
  METHODS
  Subject groups comprised patients with chronic schizophrenia (n = 16) and older control subjects (n = 13), and patients with first-episode schizophrenia (n = 21) and younger control subjects (n = 27). The MMN was visualized by subtracting the averaged event-related brain potential to standard tones (1 kHz [95% of all tones]) from the event-related brain potential to pitch-deviant tones (1.2 kHz [5% of all tones]). The MMN voltage was the mean voltage from 100 to 200 milliseconds.
  
  
  RESULTS
  Pitch-deviant MMN was reduced by approximately 47% in patients with chronic illness along the sagittal midline relative to controls. The MMN was not reduced in patients with first-episode schizophrenia. All 4 groups showed approximately 64% larger MMN to pitch-deviant tones over the right hemisphere compared with the left hemisphere.
  
  
  CONCLUSIONS
  The pitch-deviant MMN reductions present in patients with chronic schizophrenia are not present at first hospitalization. The sensory, echoic memory functions indexed by MMN seem unaffected early in the schizophrenia disease process. Reductions in MMN amplitude may develop over time and index the progression of the disorder, although that can only be definitively determined by longitudinal assessments.
authors.affiliation: Harvard Medical School, Department of Psychiatry, McLean Hospital, Belmont, MA, USA.
authors.forename: Dean F
authors.initials: DF
authors.lastname: Salisbury
authors.forename: Martha E
authors.initials: ME
authors.lastname: Shenton
authors.forename: Carlye B
authors.initials: CB
authors.lastname: Griggs
authors.forename: Aaron
authors.initials: A
authors.lastname: Bonner-Jackson
authors.forename: Robert W
authors.initials: RW
authors.lastname: McCarley
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D000367:Age Factors; D001288:Attention / Q000502:physiology; D001303:Auditory Cortex / Q000502:physiology; D002540:Cerebral Cortex / Q000502:physiology; D002908:Chronic Disease; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D007839:Functional Laterality / Q000502:physiology; D006760:Hospitalization; D006801:Humans; D008297:Male; D008568:Memory / Q000502:physiology; D009483:Neuropsychological Tests; D010898:Pitch Perception / Q000502:physiology*; D011569:Psychiatric Status Rating Scales; D012559:Schizophrenia / Q000175:diagnosis* / Q000503:physiopathology; D012565:Schizophrenic Psychology; D014796:Visual Perception / Q000502:physiology