title: Pathways that make voices: white matter changes in auditory hallucinations.
abstract: BACKGROUND
  The origin of auditory hallucinations, which are one of the core symptoms of schizophrenia, is still a matter of debate. It has been hypothesized that alterations in connectivity between frontal and parietotemporal speech-related areas might contribute to the pathogenesis of auditory hallucinations. These networks are assumed to become dysfunctional during the generation and monitoring of inner speech. Magnetic resonance diffusion tensor imaging is a relatively new in vivo method to investigate the directionality of cortical white matter tracts.
  
  
  OBJECTIVE
  To investigate, using diffusion tensor imaging, whether previously described abnormal activation patterns observed during auditory hallucinations relate to changes in structural interconnections between the frontal and parietotemporal speech-related areas.
  
  
  METHODS
  A 1.5 T magnetic resonance scanner was used to acquire twelve 5-mm slices covering the Sylvian fissure. Fractional anisotropy was assessed in 13 patients prone to auditory hallucinations, in 13 patients without auditory hallucinations, and in 13 healthy control subjects. Structural magnetic resonance imaging was conducted in the same session. Based on an analysis of variance, areas with significantly different fractional anisotropy values between groups were selected for a confirmatory region of interest analysis. Additionally, descriptive voxel-based t tests between the groups were computed.
  
  
  RESULTS
  In patients with hallucinations, we found significantly higher white matter directionality in the lateral parts of the temporoparietal section of the arcuate fasciculus and in parts of the anterior corpus callosum compared with control subjects and patients without hallucinations. Comparing patients with hallucinations with patients without hallucinations, we found significant differences most pronounced in the left hemispheric fiber tracts, including the cingulate bundle.
  
  
  CONCLUSIONS
  Our findings suggest that during inner speech, the alterations of white matter fiber tracts in patients with frequent hallucinations lead to abnormal coactivation in regions related to the acoustical processing of external stimuli. This abnormal activation may account for the patients' inability to distinguish self-generated thoughts from external stimulation.
authors.affiliation: Department of Psychiatric Neurophysiology, University Hospital of Clinical Psychiatry, Bern, Switzerland. hubl@puk.unibe.ch
authors.forename: Daniela
authors.initials: D
authors.lastname: Hubl
authors.forename: Thomas
authors.initials: T
authors.lastname: Koenig
authors.forename: Werner
authors.initials: W
authors.lastname: Strik
authors.forename: Andrea
authors.initials: A
authors.lastname: Federspiel
authors.forename: Roland
authors.initials: R
authors.lastname: Kreis
authors.forename: Chris
authors.initials: C
authors.lastname: Boesch
authors.forename: Stephan E
authors.initials: SE
authors.lastname: Maier
authors.forename: Gerhard
authors.initials: G
authors.lastname: Schroth
authors.forename: Karl
authors.initials: K
authors.lastname: Lovblad
authors.forename: Thomas
authors.initials: T
authors.lastname: Dierks
mesh_terms: D000328:Adult; D016880:Anisotropy; D002540:Cerebral Cortex / Q000503:physiopathology*; D003337:Corpus Callosum / Q000503:physiopathology; D038524:Diffusion Magnetic Resonance Imaging / Q000706:statistics & numerical data; D005260:Female; D005625:Frontal Lobe / Q000503:physiopathology; D007839:Functional Laterality / Q000502:physiology; D006212:Hallucinations / Q000175:diagnosis / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008959:Models, Neurological; D009434:Neural Pathways / Q000503:physiopathology; D010296:Parietal Lobe / Q000503:physiopathology; D011569:Psychiatric Status Rating Scales; D012559:Schizophrenia / Q000175:diagnosis / Q000503:physiopathology*; D012565:Schizophrenic Psychology; D013067:Speech Perception / Q000502:physiology*; D013702:Temporal Lobe / Q000503:physiopathology