M146. NEUROCHEMICAL MODULATION OF AUDITORY CORTEX FUNCTIONAL CONNECTIVITY IN PATIENTS WITH AUDITORY VERBAL HALLUCINATIONS

BACKGROUND: Auditory hallucinations have been linked to aberrant functioning of the left superior temporal gyrus (STG) and are associated with impaired cognitive control regulated by areas in the prefrontal cortex. However, the mechanisms behind these dysfunctions are still unclear. METHODS: The current study combined resting state connectivity fMRI with MR spectroscopy (MRS) in a sample of 81 psychosis patients to explore how neurochemical correlates of auditory hallucinations modulate left STG functioning. The analyses were focused on glutamate (Glu) and gamma-aminobutyric acid (GABA), two neurotransmitters with excitatory and inhibitory functions, respectively, since these have previously been implicated in psychosis. RESULTS: Glu and GABA showed differential relationships with left STG connectivity in patients with and without hallucinations. Specifically, Glu concentration in the anterior cingulate cortex (ACC) was positively related to functional connectivity between the left and right temporal lobe in hallucinating patients only. In contrast, GABA concentration in the ACC was negatively related to connectivity between the left and right temporal lobe in non-hallucinating patients only. DISCUSSION: These findings support a recently proposed model of interhemispheric temporal lobe miscommunication in auditory hallucinations and indicate prefrontal neurochemical modulation as a potential underlying mechanism. The results can further be integrated with previously suggested excitatory/inhibitory imbalances as neurochemical modulators in AVH.