title: Left hemisphere lateralisation of auditory hallucinations in schizophrenia: a dichotic listening study.
abstract: BACKGROUND
  We propose that auditory hallucinations are internally generated speech misrepresentations that are lateralised to the left temporal lobe. If hallucinations are misrepresentations involving the speech perception area of the left temporal lobe, then hallucinating patients should have problems identifying a simultaneously presented external speech sound, especially when the sound is lateralised to the left hemisphere. Lateralisation of speech perception can be experimentally studied with the dichotic listening task with consonant-vowel syllables. We predicted a negative relation between frequency of auditory hallucinations and performance on the dichotic listening task.
  
  
  METHODS
  We studied 87 right-handed patients with schizophrenia. Hallucination scores were taken from the BPRS symptom scale. Right and left ear scores in the dichotic listening task were recorded. A right ear advantage is expected in healthy individuals, indicating left temporal lobe processing superiority. The patients were compared with 36 right-handed healthy reference subjects.
  
  
  RESULTS
  A gradual decrease in the ability to process and report the right ear stimulus with increasing frequency of hallucinations was seen in the schizophrenia patients. No such relationship was found for processing and reporting of the left ear stimulus. There were no significant correlations with negative symptoms. Thus, the results were not the consequence of illness severity. There was however a significant correlation with unusual thought content symptom, pointing to a relationship also between delusions and auditory hallucinations.
  
  
  CONCLUSIONS
  The results support that auditory hallucinations may be internally generated speech misrepresentations, originating in the left temporal lobe.
authors.affiliation: Department of Biological and Medical Psychology, University of Bergen, Bergen, Norway. hugdahl@psybp.uib.no
authors.forename: Kenneth
authors.initials: K
authors.lastname: Hugdahl
authors.forename: Else-Marie
authors.initials: EM
authors.lastname: Løberg
authors.forename: Hugo A
authors.initials: HA
authors.lastname: Jørgensen
authors.forename: Arvid
authors.initials: A
authors.lastname: Lundervold
authors.forename: Anders
authors.initials: A
authors.lastname: Lund
authors.forename: Michael F
authors.initials: MF
authors.lastname: Green
authors.forename: Bjørn
authors.initials: B
authors.lastname: Rund
mesh_terms: D000328:Adult; D001921:Brain / Q000503:physiopathology*; D004007:Dichotic Listening Tests; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006212:Hallucinations / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology*; D006801:Humans; D008297:Male; D012559:Schizophrenia / Q000150:complications* / Q000503:physiopathology*; D012720:Severity of Illness Index