Evaluating delay of gamma oscillations in patients with schizophrenia using evoked response audiometry system.

Impaired gamma oscillations found in a 40-Hz auditory steady-state response (ASSR) in patients with schizophrenia are the robust findings that can be used for future biomarker-based therapeutics. To apply these significant observations into the clinical practice, a clinical system for evoked response audiometry (ERA) may be available. In this study, the delayed 40-Hz ASSR, which was reported as a potent biomarker for schizophrenia, was examined using the ERA system in patients with schizophrenia and its clinical relevance was investigated. The phase of ASSR was significantly delayed in patients with schizophrenia compared with the healthy subjects. The delayed phase was associated with severity of the disease symptoms in the patients. A phase delay with aging was found in healthy subjects, but not in patients with schizophrenia. These findings show availability of the ERA system to identify the delayed 40-Hz ASSR and its clinical implication in patients with schizophrenia. Further applications of the ERA system in clinical psychiatry are warranted in developing biological assessments of schizophrenia with 40-Hz ASSR.

Application of evoked response audiometry for specifying aberrant gamma oscillations in schizophrenia.

Gamma oscillations probed using auditory steady-state response (ASSR) are promising clinical biomarkers that may give rise to novel therapeutic interventions for schizophrenia. Optimizing clinical settings for these biomarker-driven interventions will require a quick and easy assessment system for gamma oscillations in psychiatry. ASSR has been used in clinical otolaryngology for evoked response audiometry (ERA) in order to judge hearing loss by focusing on the phase-locked response detectability via an automated analysis system. Herein, a standard ERA system with 40- and 46-Hz ASSRs was applied to evaluate the brain pathophysiology of patients with schizophrenia. Both ASSRs in the ERA system showed excellent detectability regarding the phase-locked response in healthy subjects and sharply captured the deficits of the phase-locked response caused by aberrant gamma oscillations in individuals with schizophrenia. These findings demonstrate the capability of the ERA system to specify patients who have aberrant gamma oscillations. The ERA system may have a potential to serve as a real-world clinical medium for upcoming biomarker-driven therapeutics in psychiatry.

Application of Near-Infrared Spectroscopy for Understanding Spontaneous Brain Activity During Resting State in Schizophrenia: A Mini Review.

Spontaneous brain activity occurs at rest, as represented by the default mode network. A resting paradigm is suitable for investigating brain function of patients with psychiatric diseases who may have difficulties adhering to goal-oriented tasks. Evidence accumulated in neuroimaging studies using functional magnetic resonance imaging has shown that the resting cerebral blood flow is impaired in psychiatric diseases. Near-infrared spectroscopy (NIRS), a simple neuroimaging modality, is an optimal tool for the resting paradigm, because it can offer a comfortable environment for measurement. Recent NIRS studies have demonstrated some promising data of altered resting activity in the prefrontal cortex of patients with schizophrenia, which may be exploited to develop further applications of NIRS in clinical psychiatry. Based on these findings, we emphasize the benefits of NIRS for assessing the prefrontal pathophysiology during the resting state and some methodological issues to be noted while analyzing cerebral blood flow using NIRS; moreover, we focus on interpreting these changes based on the complex nature of the spontaneous brain activity during resting state.

A decrease in spontaneous activity in medial prefrontal cortex is associated with sustained hallucinations in chronic schizophrenia: An NIRS study.

In functional imaging, accumulating evidence suggests that spontaneous activity decreases during the resting state in the core brain regions of the default-mode network [e.g. medial prefrontal cortex (mPFC)] in schizophrenia. However, the significance of this decreased activity has not been clarified in relation to its clinical symptoms. In this study, near-infrared spectroscopy (NIRS), which is a simple imaging modality suitable for resting state paradigm, was used to evaluate the intensity of the spontaneous activity during the resting state in chronic schizophrenia. Consistent with previous findings of fMRI studies, spontaneous activity decreased in the mPFC of patients with schizophrenia. In addition, the decreased spontaneous activity was associated with severe hallucinations in this region where reality monitoring is fundamentally engaged. These results may encourage additional application of NIRS with the resting state paradigm into daily clinical settings for addressing the broad phenotypes and unstable course of schizophrenia.

Reduced GluN1 in mouse dentate gyrus is associated with CA3 hyperactivity and psychosis-like behaviors.

Recent findings from in vivo-imaging and human post-mortem tissue studies in schizophrenic psychosis (SzP), have demonstrated functional and molecular changes in hippocampal subfields that can be associated with hippocampal hyperexcitability. In this study, we used a subfield-specific GluN1 knockout mouse with a disease-like molecular perturbation expressed only in hippocampal dentate gyrus (DG) and assessed its association with hippocampal physiology and psychosis-like behaviors. First, we used whole-cell patch-clamp recordings to measure the physiological changes in hippocampal subfields and cFos immunohistochemistry to examine cellular excitability. DG-GluN1 KO mice show CA3 cellular hyperactivity, detected using two approaches: (1) increased excitatory glutamate transmission at mossy fibers (MF)-CA3 synapses, and (2) an increased number of cFos-activated pyramidal neurons in CA3, an outcome that appears to project downstream to CA1 and basolateral amygdala (BLA). Furthermore, we examined psychosis-like behaviors and pathological memory processing; these show an increase in fear conditioning (FC), a reduction in prepulse inhibition (PPI) in the KO animal, along with a deterioration in memory accuracy with Morris Water Maze (MWM) and reduced social memory (SM). Moreover, with DREADD vectors, we demonstrate a remarkably similar behavioral profile when we induce CA3 hyperactivity. These hippocampal subfield changes could provide the basis for the observed increase in human hippocampal activity in SzP, based on the shared DG-specific GluN1 reduction. With further characterization, these animal model systems may serve as targets to test psychosis mechanisms related to hippocampus and assess potential hippocampus-directed treatments.

Mitochondrial DNA Copy Number Raises the Potential of Left Frontopolar Hemodynamic Response as a Diagnostic Marker for Distinguishing Bipolar Disorder From Major Depressive Disorder.

Background: Given a lack of markers, diagnoses of bipolar disorder (BD) and major depressive disorder (MDD) rely on clinical assessment of symptoms. However, the depressive mood states of BD and depressive symptoms of MDD are often difficult to distinguish, which leads to misdiagnoses, which in turn leads to inadequate treatment. Previous studies have shown that the hemodynamic responses of the left frontopolar cortex measured by near-infrared spectroscopy (NIRS) differ between BD and MDD; these hemodynamic responses are associated with altered mitochondrial metabolism; and mitochondrial DNA copy number (mtDNAcn), an index of mitochondrial dysfunction, tends to decrease in BD and increase in MDD patients. In this study, we confirmed that mtDNAcn trends in opposite directions in BD and MDD. We then determined whether mtDNAcn could enhance the utility of NIRS as a diagnostic marker to distinguish between BD and MDD. Methods: We determined mtDNAcn in peripheral blood samples from 58 healthy controls, 79 patients with BD, and 44 patients with MDD. Regional hemodynamic responses during a verbal fluency task (VFT) in 24 BD patients and 44 MDD patients, matched by age and depression severity, were monitored using NIRS. Results: Measurements of mtDNAcn were lower in BD patients and higher in MDD patients than in controls. The left frontopolar region exhibited the most significant differences in mean VFT-related oxy-Hb changes between the BD and MDD groups. Multivariate logistic regression analysis with variables including age, sex, hemodynamic response of the left frontopolar region, and mtDNAcn showed high accuracy for distinguishing BD from MDD (area under the curve = 0.917; 95% confidence interval = 0.849-0.985). For the BD group, we observed a positive correlation between hemodynamic responses in the left frontopolar region and mtDNAcn, while for the MDD group, we observed a negative correlation. Conclusions: Our findings suggest that the association between hemodynamic response and mitochondrial dysfunction in BD or MDD plays an important role in differentiating the pathophysiological mechanisms of BD from those of MDD.

Capturing spontaneous activity in the medial prefrontal cortex using near-infrared spectroscopy and its application to schizophrenia.

Near-infrared spectroscopy (NIRS) is an optimal imaging modality used to examine spontaneous brain activity because it can quietly measure blood flow changes with less physical restriction during the resting state. Here, NIRS was used at rest to measure spontaneous activity in the medial prefrontal cortex (mPFC), a main locus of default mode network. Consistent with previous fMRI studies, magnitude of the spontaneous activity in this region declined with increasing age in healthy subjects. The magnitude reduced in the mPFC of patients with schizophrenia. Additionally, in the mPFC of patients with schizophrenia, the spontaneous activity did not show any age-related decline; the activity was already low in younger patients. Further analysis using fractional amplitude of low-frequency fluctuations confirmed the reduction of spontaneous activity in the mPFC of patients with schizophrenia, consistent with the findings of fMRI studies. Our findings demonstrate the ability of NIRS to evaluate the spontaneous activity in the mPFC of patients with schizophrenia, particularly younger patients. Considering the safety and ease of the NIRS measurements, the current NIRS study of the resting-state activity indicates its utility for clinical applications to schizophrenia, which may facilitate chronological assessment of larger cohorts of patients with schizophrenia in further studies.

Mitochondrial DNA copy number of peripheral blood in bipolar disorder: The present study and a meta-analysis.

Numerous evidence indicated mitochondrial abnormalities in the pathophysiology of bipolar disorder (BD); however, it remains unclear whether aberrant mitochondrial DNA (mtDNA) copy number (cn) occur in BD due to the conflicting results in previous studies. Here, peripheral blood mtDNAcn in 69 BD patients and 54 controls were analysed via qPCR. BD patients had significantly lower mtDNAcn compared to controls (regardless of their BD type [BD I or II]). Meta-analysis for all previous BD-mtDNAcn studies combining our results with previously published studies failed to identify any significant association. Meanwhile, Asian-specific meta-analysis remarkably revealed lower mtDNAcn in BD patients.

Repetition of verbal fluency task attenuates the hemodynamic activation in the left prefrontal cortex: Enhancing the clinical usefulness of near-infrared spectroscopy.

In applications of near-infrared spectroscopy (NIRS) in clinical psychiatry settings in Japan, a phonemic verbal fluency test (VFT) that includes "switching" (the ability to shift efficiently to a new word subcategory) to assess phonemic fluency is employed to capture disease-specific hemodynamic changes in the prefrontal cortex (PFC). In this study, to extend the specific features of this test, the VFT was repeated to examine an activation change in NIRS measurements in 20 healthy males. Without task performance change, the hemodynamic activation induced by the VFT was significantly attenuated in the left PFC through repetition of the task. These findings suggest that the left PFC is involved in processing of the VFT. Further, it may be possible to extend the current VFT using this repetition to provide a more sensitive examination of the left PFC, whose dysfunction has been reported in several psychiatric diseases such as major depression, bipolar disorder, and schizophrenia.

Right temporal activation differs between melancholia and nonmelancholic depression: a multichannel near-infrared spectroscopy study.

The aim of this study was to determine whether melancholia differs from nonmelancholic depression in frontotemporal functioning by means of multichannel near-infrared spectroscopy. We recruited 32 major depressive disorder (MDD) patients with melancholic features (MDD-MF), 28 MDD patients with nonmelancholic features (MDD-NMF), and 24 healthy controls. Regional hemodynamic changes induced by a verbal fluency task (VFT) were monitored, and their correlations with depressive symptoms were examined. In comparison with the controls, significant differences were observed in mean oxygenated hemoglobin (oxy-Hb) changes induced by VFT in patients with MDD-MF in 25 channels (p = 0.000-0.047) and in those with MDD-NMF in 12 channels (p = 0.000-0.023). Moreover, patients with MDD-MF had significantly smaller mean oxy-Hb changes than those with MDD-NMF in 8 channels of the right temporal region (p = 0.001-0.048). No significant correlations were observed between mean oxy-Hb changes and the Hamilton rating scale for depression (HAMD) 17 total score in both groups of patients with MDD. On examining each item of HAMD17, psychomotor retardation in patients with MDD-MF showed a significant positive correlation with mean oxy-Hb changes in the right temporal region (ch43; ρ = 0.55; p = 0.001), whereas that in patients with MDD-NMF showed a significant negative correlation with mean oxy-Hb changes in the frontal and left temporal regions in 3 channels (ρ = -0.60 to -0.53; p = 0.000-0.004). In conclusion, our results indicate that melancholia is qualitatively distinct from nonmelancholic depression both clinically and biologically.

Animal models of schizophrenia emphasizing construct validity.

Achieving animal models of schizophrenia which are representative of clear aspects of the illness is critical to understanding pathophysiology and developing novel treatments for the complex syndrome. This chapter reviews the various approaches that have been used in the past to create animal models of schizophrenia, including pharmacological approaches, environmental risk conditions and schizophrenia risk genes. In addition, we present a new animal model which derives directly from human tissue and brain imaging data used to develop a human schizophrenia model. This chapter emphasizes the crucial need for construct validity and of modeling discrete elements of schizophrenia's illness presentation as the way to successful advances.

Association of calcineurin A gamma subunit (PPP3CC) and early growth response 3 (EGR3) gene polymorphisms with susceptibility to schizophrenia in a Japanese population.

To examine the association of PPP3CC (rs10108011 and rs2461491) and EGR3 (rs3750192) single-nucleotide polymorphisms (SNPs) with Japanese schizophrenia, we performed a case-control association study using 337 patients and 369 healthy controls. As a result, by our moderated cohort-size study, PPP3CC and EGR3 are not genetic risk factors for schizophrenia, whereas meta-analysis showed weak association of rs10108011 with schizophrenia in the Japanese population (odds ratio (OR)=1.12, P=0.01).

A putative cis-acting polymorphism in the NOS1 gene is associated with schizophrenia and NOS1 immunoreactivity in the postmortem brain.

Schizophrenia is a devastating neurodevelopmental disorder whose genetic influences remain elusive. Recent genome-wide scans revealed that rare structural variants disrupted multiple genes in neurodevelopmental pathways, which strongly implicate nitric oxide (NO) signaling in schizophrenia. NO acts as a second messenger of N-methyl-D aspartate receptor activation, which further interacts with both dopaminergic and serotonergic pathways. NO is mainly synthesized by neuronal nitric oxide synthase (NOS1) in the brain, and its gene locus, 12q24.2, has attracted much attention as a major linkage region for schizophrenia. Genetic variations of NOS1 have also been associated with schizophrenia, and differential expression of NOS1 was observed in the postmortem brain of schizophrenic patients. Here, we explored the hypothesis that a putative cis-acting G-84A single nucleotide polymorphism (SNP; rs41279104) in the exon 1c promoter region of the NOS1 gene is associated with the levels of NOS1 immunoreactivity in postmortem prefrontal cortex specimens regardless of disease phenotype. Individuals with the A-allele of this SNP showed significantly lower levels of NOS1 immunoreactivity than did GG homozygotes (p=0.002). Furthermore, a case-control study using 720 individuals in a Japanese population revealed a significant association between the SNP and schizophrenia (genotypic p=0.0013 and allelic p=0.0011). Additionally, the average of onset age in schizophrenic patients with the A-allele was significantly earlier than GG homozygotes (p=0.018). When the analyses took gender into account, this significance was more significant for female. These findings provide further evidences that NOS1 is associated with a biological susceptibility gene to schizophrenia.

Expression of Kruppel-like factor 5 gene in human brain and association of the gene with the susceptibility to schizophrenia.

Genome-wide gene expression analysis using DNA microarray technology is a potential tool to search for unexpected genes that have a susceptibility to schizophrenia. We carried out a microarray analysis in the postmortem prefrontal cortex and found that the expression of the KLF5 gene, whose locus is on 13q21, was down-regulated in schizophrenia patients. This result was confirmed by a Western blot analysis. In a genetic study, we found that a polymorphism of the KLF5 gene (-1593T>C) was associated with schizophrenia. We identified neurons in the prefrontal cortex of human brain as sites of KLF5 expression by in situ hybridization and immunohistochemistry. KLF5 was immunohistochemically localized in granular and pyramidal cells in the hippocampus, which are the principal source of glutamatergic neurotransmission. These findings suggest that the KLF5 gene is a novel schizophrenia-susceptibility gene, and that the expression of the gene is involved in the pathophysiology of schizophrenia via glutamatergic neurotransmission.

Association of RGS2 gene polymorphisms with suicide and increased RGS2 immunoreactivity in the postmortem brain of suicide victims.

Regulators of G-protein signaling are a family of proteins that negatively regulate the intracellular signaling of G protein-coupled receptors, such as the serotonin receptor. Recent studies have suggested that one of these proteins, the regulator of G-protein signaling 2 (RGS2), plays an important part in anxiety and/or aggressive behavior. To explore the involvement of the RGS2 gene in the vulnerability to suicide, we screened Japanese suicide victims for sequence variations in the RGS2 gene and carried out an association study of RGS2 gene polymorphisms with suicide victims. In the eight identified polymorphisms that were identified by mutation screening, we genotyped four common single-nucleotide polymorphisms (SNPs) in the RGS2 gene, and found significant differences in the distribution of the SNP3 (C+2971G, rs4606) genotypes and alleles of the SNP2 (C-395G, rs2746072) and the SNP3 between completed suicides and the controls. The distribution of the haplotype was also significantly different between the two groups (global p<0.0001). Furthermore, RGS2 immunoreactivity significantly increased in the amygdala and the prefrontal cortex (Brodmann area 9 (BA9)) of the postmortem brain of the suicide subjects. These findings suggest that RGS2 is genetically involved in the biological susceptibility to suicide in the Japanese population.

Association of 14-3-3 epsilon gene haplotype with completed suicide in Japanese.

Genetic factors have been suggested to be involved in suicide. Although some genetic factors, such as serotonergic transduction, have been associated with suicide, the results are inconsistent. There is a possibility that various signaling anomalies are involved in the biological vulnerability to suicide. We carried out a genome-wide gene-expression study in the brains of suicide victims using DNA microarrays;14-3-3 epsilon, which is related to neurogenesis, was one of the genes upregulated in the brains of suicide victims in the microarray analysis. This was confirmed by Western blot analysis. To examine the possibility of the involvement of 14-3-3 epsilon in the pathogenesis of suicide, we investigated the association of the 14-3-3 epsilon gene and completed suicide. We used three high-frequency SNPs (rs1532976, rs3752826, and rs9393) and found a significant association of two alleles (rs1532976 and rs3752826) with completed suicide (p < 0.05). Moreover, the distribution of haplotype revealed a more significant difference between completed suicide and controls (p=0.0005). This finding suggests that 14-3-3 epsilon is a potential suicide susceptibility gene and implies that dysregulation of neurogenesis may be involved in suicide.