Network dynamics during the different stages of hallucinations in schizophrenia
Résumé
The majority of patients with schizophrenia suffer from hallucinations. While the triple-network model, which includes the default mode network (DMN), the central executive network (CEN) and the salience network (SAL), has recently been applied to schizophrenia, how this framework could explain the emergence of hallucinations remains unclear. Therefore, complementary brain regions that have been linked to hallucinations, such as the left hippocampus, should also be considered and added to this model. Accordingly, the present study explored the effective connectivity across these four components (i.e., the quadripartite model) during the different stages of hallucinations. Twenty-five patients with schizophrenia participated in a single session of resting-state functional magnetic resonance imaging to capture hallucinatory experiences. Based on the participants' self-report of the psychosensory experiences that occurred during scanning, hallucinatory experiences were identified and divided into four stages: periods without hallucination ("OFF"), periods with hallucination ("ON"), transition periods between "OFF" and "ON", and the extinction of the hallucinatory experience ("END"). Using stochastic dynamic causal modeling analysis, this study first confirmed that the SAL played a critical and causal role in switching between the CEN and the DMN in schizophrenia. In addition, effective connectivity within the quadripartite model depended on the hallucinatory stage. In particular, "ON" periods were linked to memory-based sensory input from the hippocampus to the SAL, while "END" periods were associated with a takeover of the CEN in favor of a voluntary process. Finally, the pathophysiological and therapeutic implications of these findings are critically discussed.
Mots clés
intrinsic connectivity networks
effective connectivity
hallucinations
schizophrenia
brain imaging
dynamic causal modeling
Mesh:Hallucinations/physiopathology*
Mesh:Humans
Mesh:Male
Mesh:Models
Mesh:Neurological
Mesh:Neural Pathways/diagnostic imaging
Mesh:Neural Pathways/physiopathology
Mesh:Psychiatric Status Rating Scales
Mesh:Brain/diagnostic imaging
Mesh:Bayes Theorem
Mesh:Adult
Mesh:Schizophrenia/physiopathology*
Mesh:Schizophrenia/diagnostic imaging
Mesh:Rest
Mesh:Brain Mapping
Mesh:Brain/physiopathology*
Mesh:Self Report
Mesh:Female
Mesh:Hallucinations/diagnostic imaging