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Auditory verbal hallucinations and language lateralization

Research output: Chapter in Book/Report/Conference proceedingChapter

Kelly Diederen, Iris E.C. Sommer

Original languageEnglish
Title of host publicationLanguage Lateralization and Psychosis
PublisherCambridge University Press
Pages157-168
Number of pages12
ISBN (Electronic)9780511576744
ISBN (Print)9780521882842
DOIs
Publication statusPublished - 1 Jan 2009

King's Authors

Abstract

The pathophysiology of auditory verbal hallucinations (AVH) is largely unknown. Several functional imaging studies have measured cerebral activation during AVH, but sample sizes were relatively small (1-8 subjects) and findings were inconsistent. In this chapter we describe cerebral activation during AVH in a relatively large sample to enable group-wise analysis and obtain a representative view of the biological substrate of hallucinations. Activity during AVH is compared to activity during normal language production in the same patients. We measured cerebral activation with fMRI in 24 psychotic patients while they experienced AVH in the scanner, and also while they silently generated words (verbal fluency). Patients indicated the presence of AVH by squeezing a balloon with their right hand. Patients were right-handed and diagnosed with schizophrenia, schizo-affective disorder, or psychosis NOS (not otherwise specified). Despite adequate pharmacotherapy, patients experienced AVH frequently. Group-wise analysis was performed on 24 fMRI scans during AVH and during word generation. Lateralization indices of both conditions were compared. Group analysis for AVH revealed activation in the right homolog of Broca’s area, bilateral insula, bilateral supramarginal gyri, right superior temporal gyrus, and in motor related areas (associated with squeezing the balloon). Broca’s area and left superior temporal gyrus were not activated during AVH, nor were the hippocampi. Group analysis for word generation yielded activation in Broca’s and Wernicke’s area and to a lesser degree their right-sided homologs, bilateral insula, and anterior cingulate gyrus. The mean lateralization index during hallucinations (−0.11, SD = 0.41) was significantly lower than during word generation (+ 0.14, SD = 0.34) (T (23) = −2.4, p < 0.02). Lateralization of activity during AVH was not correlated with language lateralization, but rather with the degree to which the content of the AVH had a negative emotional valence. The main difference between cerebral activity during AVH and activity during normal inner speech appears to be the lateralization. The predominant engagement of the right inferior frontal area during AVH may be related to the typical low semantic complexity and negative emotional content of AVH.

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