Cerebral activity associated with auditory verbal hallucinations: a functional magnetic resonance imaging case study

TLDR

Auditory verbal hallucinations are thought to arise either from misinterpreted inner speech or from aberrant activation of the primary auditory cortex. The study examined whether these hypotheses hold by observing a schizophrenic patient whose hallucinations ceased when she listened to loud external speech. Functional MRI recorded activity in the patient’s temporal and inferior frontal regions during hallucinations and during listening, with a matched control scanned under identical conditions. Hallucinations were linked to heightened activity in the left primary auditory cortex and right middle temporal gyrus, indicating a possible interaction that supports both hypotheses. Limitations to generalizing the findings are acknowledged.

Abstract

Among the many theories that have been advanced to explain the mechanism by which auditory verbal hallucinations (AVH) arise, 2 that have received a degree of empirical support are: the hypothesis that AVHs arise from misinterpreted inner speech and the proposal that they arise from aberrant activation of the primary auditory cortex. To test these hypotheses, we were fortunate to be able to study the interesting and rare case of a woman with schizophrenia who experienced continuous AVH which disappeared when she listened to loud external speech. Functional magnetic resonance imaging (fMRI) was used to measure the patient’s brain activity in the temporal and inferior frontal regions during the AVHs and while the she was listening to external speech. The brain activity of a matched control subject was also recorded under the same experimental conditions. AVHs were associated with increased metabolic activity in the left primary auditory cortex and the right middle temporal gyrus. Our results suggest a possible interaction between these areas during AVHs and also that the hypotheses of defective internal monitoring and aberrant activation are not mutually exclusive. Potential limitations to the generalization of our results are discussed.