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Background: Auditory hallucinations (AH) are typically associated with schizophrenia (SZ), but they are also prevalent in bipolar disorder (BD). Despite the large body of research on the neural correlates of AH in SZ, the pathophysiology underlying AH remains unclear. Few studies have examined the neural substrates associated with propensity for AH in BD. Investigating AH across the psychosis spectrum has the potential to inform about the neural signature associated with the trait of AH, irrespective of psychiatric diagnosis., Methods: We compared resting state functional magnetic resonance imaging data in psychosis patients with (n = 90 AH; 68 SZ, 22 BD) and without (n = 55 NAH; 16 SZ, 39 BD) lifetime AH. We performed region of interest (ROI)-to-ROI functional connectivity (FC) analysis using 91 cortical, 15 subcortical, and 26 cerebellar atlas-defined regions. The primary aim was to identify FC differences between patients with and without lifetime AH. We secondarily examined differences between AH and NAH within each diagnosis., Results: Compared to the NAH group, patients with AH showed higher FC between cerebellum and frontal (left precentral gyrus), temporal [right middle temporal gyrus (MTG), left inferior temporal gyrus (ITG), left temporal fusiform gyrus)], parietal (bilateral superior parietal lobules), and subcortical (left accumbens, left palldium) brain areas. AH also showed lower FC between temporal lobe regions (between right ITG and right MTG and bilateral superior temporal gyri) relative to NAH., Conclusions: Our findings suggest that dysconnectivity involving the cerebellum and temporal lobe regions may be common neurofunctional elements associated with AH propensity across the psychosis spectrum. We also found dysconnectivity patterns that were unique to lifetime AH within SZ or bipolar psychosis, suggesting both common and distinct mechanisms underlying AH pathophysiology in these disorders., (Copyright © 2021. Published by Elsevier Inc.)

Background: In schizophrenia (SZ), disturbances in integration of activity among brain regions seem to be as important as abnormal activity of any single region. Brain regions are connected through white matter (WM) tracts, and diffusion tensor imaging has provided compelling evidence for WM abnormalities in SZ. However, diffusion tensor imaging alone cannot currently pinpoint the biological basis of these abnormalities., Methods: In this study, we combined a myelin-specific and an axon-specific magnetic resonance imaging approach to examine potentially distinct abnormalities of WM components in SZ. Magnetization transfer ratio (MTR) provides information on myelin content, whereas diffusion tensor spectroscopy provides information on metabolite diffusion within axons. We collected data from a 1 × 3 × 3 cm voxel within the right prefrontal cortex WM at 4 Tesla and studied 23 patients with SZ and 22 age- and sex-matched healthy control participants., Results: The MTR was significantly reduced in SZ, suggesting reduced myelin content. By contrast, the apparent diffusion coefficient of N-acetylaspartate (NAA) was significantly elevated, suggesting intra-axonal abnormalities. Greater abnormality of both MTR and the apparent diffusion coefficient of NAA correlated with more adverse outcomes in the patient group., Conclusions: The results suggest that WM abnormalities in SZ include both abnormal myelination and abnormal NAA diffusion within axons. These processes might be associated with abnormal signal transduction and abnormal information processing in SZ., (Copyright © 2013 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.)

Background: Sleep spindles are thought to induce synaptic changes and thereby contribute to memory consolidation during sleep. Patients with schizophrenia show dramatic reductions of both spindles and sleep-dependent memory consolidation, which may be causally related., Methods: To examine the relations of sleep spindle activity to sleep-dependent consolidation of motor procedural memory, 21 chronic, medicated schizophrenia outpatients and 17 healthy volunteers underwent polysomnography on two consecutive nights. On the second night, participants were trained on the finger-tapping motor sequence task (MST) at bedtime and tested the following morning. The number, density, frequency, duration, amplitude, spectral content, and coherence of stage 2 sleep spindles were compared between groups and examined in relation to overnight changes in MST performance., Results: Patients failed to show overnight improvement on the MST and differed significantly from control participants who did improve. Patients also exhibited marked reductions in the density (reduced 38% relative to control participants), number (reduced 36%), and coherence (reduced 19%) of sleep spindles but showed no abnormalities in the morphology of individual spindles or of sleep architecture. In patients, reduced spindle number and density predicted less overnight improvement on the MST. In addition, reduced amplitude and sigma power of individual spindles correlated with greater severity of positive symptoms., Conclusions: The observed sleep spindle abnormalities implicate thalamocortical network dysfunction in schizophrenia. In addition, the findings suggest that abnormal spindle generation impairs sleep-dependent memory consolidation in schizophrenia, contributes to positive symptoms, and is a promising novel target for the treatment of cognitive deficits in schizophrenia., (Copyright © 2012 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.)