398. Functional MRI studies of auditory hallucinations

Abstract

We used functional MRI to examine the neural correlates of 1) cognitive processes putatively relevant to auditory hallucinations, and 2) auditory hallucinations themselves. Images were acquired on a 1.5T system and analysed using nonparametric methods. In study 1, patients with schizophrenia who had a history of frequent hallucinations were compared with volunteers. Images were acquired while subjects imagined another person’s speech, which entails the implicit generation and monitoring of inner speech. Volunteers engaged a network of areas including the inferior frontal and temporal cortex bilaterally, the SMA, cingulate cortex, and the cerebellar cortex. Patients prone to hallucinations differed from controls in showing attenuated activation in the lateral temporal cortex and fusiform gyrus/cerebellum. Study 2 employed a within-subject event related design, comparing activity in patients with schizophrenia when they were and were not experiencing auditory hallucinations. Hallucinations were associated with activation in a network that resembled that engaged during imagining speech, except that there was an absence of activation in the SMA and cerebellum, but additional activation in the left parahippocampal cortex, and in the right thalamus and inferior colliculus. These data suggest there is a close relationship between auditory hallucinations and inner speech, and are consistent with the notion that hallucinations represent inner speech which has been misidentified as “alien” due to defective verbal self-monitoring.