title: Reduced early auditory evoked gamma-band response in patients with schizophrenia.
abstract: BACKGROUND
  There is growing evidence for abnormalities of certain gamma-aminobutyric acid (GABA)-ergic interneurons and their interaction with glutamatergic pyramidal cells in schizophrenia. These interneurons are critically involved in generating neural activity in the gamma-band (30-100 Hz) of the electroencephalogram. One example of such gamma oscillations is the early auditory evoked gamma-band response (GBR). Although auditory processing is obviously disturbed in schizophrenia, there is no direct evidence providing a reduced early auditory evoked GBR so far. We addressed two questions: 1) Is the early auditory evoked GBR decreased regarding power and phase-locking in schizophrenic patients?; and 2) Is this possible decrease a result of reduced activity in the auditory cortex and/or the anterior cingulate cortex (ACC), which were identified as sources of the GBR previously?
  
  
  METHODS
  We investigated the early auditory evoked GBR and its sources in the ACC and the auditory cortex in 90 medicated patients with schizophrenia and in age-, gender-, and education-matched healthy control subjects with an auditory reaction task.
  
  
  RESULTS
  Patients with schizophrenia showed a significant reduction of power and phase-locking of the early auditory evoked GBR. This effect was due to a reduced activity in the auditory cortex and the ACC/medial frontal gyrus region (low-resolution brain electromagnetic tomography analysis).
  
  
  CONCLUSIONS
  Generally, these findings are in line with earlier reports on the impaired ability of schizophrenic patients in generating gamma activity. In addition, this is the first study to demonstrate disturbance of gamma activity in auditory processing as assessed by the early auditory GBR power.
authors.affiliation: Department of Psychiatry and Psychotherapy, Ludwig-Maximilians-University, 7D-80336 Munich, Germany. gregor.leicht@med.uni-muenchen.de
authors.forename: Gregor
authors.initials: G
authors.lastname: Leicht
authors.forename: Valerie
authors.initials: V
authors.lastname: Kirsch
authors.forename: Ina
authors.initials: I
authors.lastname: Giegling
authors.forename: Susanne
authors.initials: S
authors.lastname: Karch
authors.forename: Irmgard
authors.initials: I
authors.lastname: Hantschk
authors.forename: Hans-Jürgen
authors.initials: HJ
authors.lastname: Möller
authors.forename: Oliver
authors.initials: O
authors.lastname: Pogarell
authors.forename: Ulrich
authors.initials: U
authors.lastname: Hegerl
authors.forename: Dan
authors.initials: D
authors.lastname: Rujescu
authors.forename: Christoph
authors.initials: C
authors.lastname: Mulert
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D001931:Brain Mapping; D016009:Chi-Square Distribution; D004569:Electroencephalography; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009716:Numerical Analysis, Computer-Assisted; D011930:Reaction Time / Q000502:physiology; D012559:Schizophrenia / Q000503:physiopathology*; D055815:Young Adult