S72. FUNCTIONAL DISCONNECTION WITHIN THE PRESENCE HALLUCINATION NETWORK IN PSYCHOTIC PATIENTS WITH FIRST-RANK SYMPTOMS

Abstract

Abstract Background Psychosis is an abnormal mental state including hallucinations and delusions, typical of psychiatric conditions such as schizophrenia. Recent theories posit that psychosis is driven by inaccurate sensorimotor predictions causing the misattribution of self-related events to external sources. This misattribution has been linked to first-rank symptoms (FRS), including a loss of sense of agency and, particularly, the occurrence of an alien agent. The subjective experience of an alien agent while no one is actually there is called presence hallucination (PH). PH has been observed in schizophrenia, Parkinson’s disease and neurological patients with circumscribed brain lesions. In healthy participants, PH can be induced by exerting sensorimotor conflicts between the participants’ upper-limb movements and a tactile feedback received on the back using MRI-compatible robotics. Crucially, the neural network associated with this robotically-induced version of PH overlap with the symptomatic-PH network derived from neurological patients suffering from PH in right dorso-lateral prefrontal cortex (dlPFC) and middle temporal gyrus (MTG), suggesting a common neural mechanism (PH network). Methods Given that experiencing an alien agent is a specific feature of FRS, we tested whether bilateral functional connectivity in PH network comprising of dlPFC and MTG can specifically differentiate psychotic patients with (N = 39) versus without (N = 24) FRS. Results We observed reduced functional connectivity in patients with FRS as compared to patients without FRS between the right MTG and the dlPFC bilaterally. Interestingly, connectivity between these areas was negatively correlated with the FRS severity (rho = -0.29 and rho = -0.26, respectively). Discussion We propose that reduced functional connectivity between the right MTG and bilateral dlPFC areas could be a specific biomarker of first rank symptoms in patients with psychosis.