title: Reduced connectivity of the auditory cortex in patients with auditory hallucinations: a resting state functional magnetic resonance imaging study.
abstract: BACKGROUND
  Previous research has reported auditory processing deficits that are specific to schizophrenia patients with a history of auditory hallucinations (AH). One explanation for these findings is that there are abnormalities in the interhemispheric connectivity of auditory cortex pathways in AH patients; as yet this explanation has not been experimentally investigated. We assessed the interhemispheric connectivity of both primary (A1) and secondary (A2) auditory cortices in n=13 AH patients, n=13 schizophrenia patients without auditory hallucinations (non-AH) and n=16 healthy controls using functional connectivity measures from functional magnetic resonance imaging (fMRI) data.
  
  
  METHODS
  Functional connectivity was estimated from resting state fMRI data using regions of interest defined for each participant based on functional activation maps in response to passive listening to words. Additionally, stimulus-induced responses were regressed out of the stimulus data and the functional connectivity was estimated for the same regions to investigate the reliability of the estimates.
  
  
  RESULTS
  AH patients had significantly reduced interhemispheric connectivity in both A1 and A2 when compared with non-AH patients and healthy controls. The latter two groups did not show any differences in functional connectivity. Further, this pattern of findings was similar across the two datasets, indicating the reliability of our estimates.
  
  
  CONCLUSIONS
  These data have identified a trait deficit specific to AH patients. Since this deficit was characterized within both A1 and A2 it is expected to result in the disruption of multiple auditory functions, for example, the integration of basic auditory information between hemispheres (via A1) and higher-order language processing abilities (via A2).
authors.affiliation: Howard Florey Institute, Florey Neuroscience Institutes, Florey Neuroscience Institutes, University of Melbourne, Parkville, 3010, Victoria, Australia. maria.gavrilescu@florey.edu.au
authors.forename: M
authors.initials: M
authors.lastname: Gavrilescu
authors.forename: S
authors.initials: S
authors.lastname: Rossell
authors.forename: G W
authors.initials: GW
authors.lastname: Stuart
authors.forename: T L
authors.initials: TL
authors.lastname: Shea
authors.forename: H
authors.initials: H
authors.lastname: Innes-Brown
authors.forename: K
authors.initials: K
authors.lastname: Henshall
authors.forename: C
authors.initials: C
authors.lastname: McKay
authors.forename: A A
authors.initials: AA
authors.lastname: Sergejew
authors.forename: D
authors.initials: D
authors.lastname: Copolov
authors.forename: G F
authors.initials: GF
authors.lastname: Egan
mesh_terms: D000328:Adult; D001303:Auditory Cortex / Q000503:physiopathology*; D005260:Female; D006212:Hallucinations / Q000175:diagnosis / Q000503:physiopathology* / Q000523:psychology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008960:Models, Psychological; D009415:Nerve Net / Q000503:physiopathology*; D012559:Schizophrenia / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology; D012720:Severity of Illness Index; D013067:Speech Perception / Q000502:physiology; D014825:Vocabulary