Hallucinations and negative symptoms differentially revealed by frontal and temporal responses to speech in schizophrenia

Hyper-Activated Brain Resting-State Network and Mismatch Negativity Deficit in Schizophrenia With Auditory Verbal Hallucination Revealed by an Event-Related Potential Evidence

Schizophrenia is a holergasia with unclear mechanism and high heterogeneity. Auditory verbal hallucination (AVH) study might help in understanding schizophrenia from the perspective of individual symptoms. This study aimed to investigate the activities of the resting-state networks (RSN) in the electroencephalogram (EEG) and mismatch negativity (MMN) in task-related state of schizophrenia patients with AVH. We recruited 30 schizophrenia patients without any medication for more than 4 weeks (15 AVH patients and 15 Non-AVH patients) and 15 healthy controls. We recorded the EEG data of the participants in the resting-state for 7 min and the event-related potential (ERP) data under an auditory oddball paradigm. In the resting-state EEG network, AVH patients exhibited a higher clustering coefficient than Non-AVH patients and healthy controls on delta and beta bands and a shorter characteristic path length than Non-AVH patients and healthy controls on all frequency bands. For ERP data, AVH patients showed a lower MMN amplitude than healthy controls (p = 0.017) and Non-AVH patients (p = 0.033). What's more, MMN amplitude was positively correlated with clustering coefficient, and negatively correlated with characteristic path length on delta, theta, beta and gamma band in AVH patients. Our results indicate that AVH patients showed a hyper-activity in resting-state and may have impaired higher-order auditory expectations in the task-related state than healthy controls and Non-AVH patients. And it seems reasonable to conclude that the formation of AVH may occupy certain brain resources and compete for brain resources with external auditory stimuli.

Resting State Effective Connectivity Allows Auditory Hallucination Discrimination

Hallucinations are elusive phenomena that have been associated with psychotic behavior, but that have a high prevalence in healthy population. Some generative mechanisms of Auditory Hallucinations (AH) have been proposed in the literature, but so far empirical evidence is scarce. The most widely accepted generative mechanism hypothesis nowadays consists in the faulty workings of a network of brain areas including the emotional control, the audio and language processing, and the inhibition and self-attribution of the signals in the auditive cortex. In this paper, we consider two methods to analyze resting state fMRI (rs-fMRI) data, in order to measure effective connections between the brain regions involved in the AH generation process. These measures are the Dynamic Causal Modeling (DCM) cross-covariance function (CCF) coefficients, and the partially directed coherence (PDC) coefficients derived from Granger Causality (GC) analysis. Effective connectivity measures are treated as input classifier features to assess their significance by means of cross-validation classification accuracy results in a wrapper feature selection approach. Experimental results using Support Vector Machine (SVM) classifiers on an rs-fMRI dataset of schizophrenia patients with and without a history of AH confirm that the main regions identified in the AH generative mechanism hypothesis have significant effective connection values, under both DCM and PDC evaluation.

Impact of childhood adversities on the short-term course of illness in psychotic spectrum disorders

Accumulating evidence indicates an impact of childhood adversities on the severity and course of mental disorders, whereas this impact on psychotic disorders remains to be specified. Effects of childhood adversities on comorbidity, on symptom severity of the Positive and Negative Syndrome Scale and global functioning across four months (upon admission, 1 and 4 months after initial assessment), as well as the course of illness (measured by the remission rate, number of re-hospitalizations and dropout rate) were evaluated in 62 inpatients with psychotic spectrum disorders. Adverse experiences (of at least 1 type) were reported by 73% of patients. Patients with higher overall level of childhood adversities (n=33) exhibited more co-morbid disorders, especially alcohol/substance abuse and dependency, and higher dropout rates than patients with a lower levels of adverse experiences (n=29), together with higher levels of positive symptoms and symptoms of excitement and disorganization. Emotional and physical neglect were particularly related to symptom severity. Results suggest that psychological stress in childhood affects the symptom severity and, additionally, a more unfavorable course of disorder in patients diagnosed with psychoses. This impact calls for its consideration in diagnostic assessment and psychiatric care.