title: Preattentive dysfunction in patients with bipolar disorder as revealed by the pitch-mismatch negativity: a magnetoencephalography (MEG) study.
abstract: OBJECTIVE
  Mismatch negativity (MMN) and its magnetic counterpart (MMNm) are thought to reflect an automatic process that detects a difference between an incoming stimulus and the sensory memory trace of preceding stimuli. In patients with schizophrenia, an attenuation of the MMN/MMNm amplitude has been repeatedly reported. Heschl's gyrus (HG) is one of the major generators of MMN and the functional alteration of HG has been reported in patients with bipolar disorder. The present study investigated the pitch-MMNm in patients with bipolar disorder using whole-head 306-ch magnetoencephalography (MEG).
  
  
  METHODS
  Twenty-two patients and 22 healthy controls participated in this study. Subjects were presented with two types of auditory stimulus sequences. One consisted of 1,000 Hz standards (probability = 90%) and 1,200 Hz deviants (probability = 10%), and the other consisted of 1,000 Hz standards (90%) and 1,200 Hz deviants (10%). These two tasks were each performed twice. Event-related brain responses to standard tones were subtracted from responses to deviant tones.
  
  
  RESULTS
  Patients with bipolar disorder showed a significant bilateral reduction in magnetic global field power (mGFP) amplitudes (p = 0.02) and dipole moments of the MMNm (p = 0.04) compared with healthy controls. Patients with admission experience showed significantly reduced mGFP amplitudes of MMNm compared with patients without admission experience (p = 0.004). Additionally, patients with more severe manic symptoms had smaller mGFP amplitudes of MMNm (ρ = -0.50, p = 0.05).
  
  
  CONCLUSIONS
  The results of this study suggest that patients with bipolar disorder may exhibit preattentive auditory dysfunction indexed by reduced pitch-MMNm responses. Pitch-MMNm could be a potential trait marker reflecting the global severity of bipolar disorder.
authors.affiliation: Department of Neuropsychiatry, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Satomi
authors.initials: S
authors.lastname: Shimano
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Onitsuka
authors.forename: Naoya
authors.initials: N
authors.lastname: Oribe
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Maekawa
authors.forename: Rikako
authors.initials: R
authors.lastname: Tsuchimoto
authors.forename: Shogo
authors.initials: S
authors.lastname: Hirano
authors.forename: Takefumi
authors.initials: T
authors.lastname: Ueno
authors.forename: Yoji
authors.initials: Y
authors.lastname: Hirano
authors.forename: Tomofumi
authors.initials: T
authors.lastname: Miura
authors.forename: Shigenobu
authors.initials: S
authors.lastname: Kanba
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D001714:Bipolar Disorder / Q000150:complications*; D001931:Brain Mapping; D003244:Consciousness Disorders / Q000175:diagnosis* / Q000209:etiology*; D003265:Contingent Negative Variation / Q000502:physiology*; D004569:Electroencephalography; D005072:Evoked Potentials, Auditory / Q000502:physiology; D005260:Female; D007839:Functional Laterality; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D008875:Middle Aged; D010897:Pitch Discrimination / Q000502:physiology*; D013223:Statistics as Topic; D055815:Young Adult
keywords: bipolar disorder; magnetoencephalography; mismatch negativity; preattentive dysfunction