Alpha oscillation mediates the interaction between suicide risk and symptom severity in Major Depressive Disorder

ObjectiveThe aim of our study was to explore the relationship between changes in neural oscillatory power in the EEG, the severity of depressive-anxiety symptoms, and the risk of suicide in MDD.Methods350 MDD patients’ demographic and clinical data were collected, and their depressive and anxious symptoms were evaluated using HDRS-17 and HAMA-14, along with a suicide risk assessment using the Nurses’ Global Assessment of Suicide Risk (NGASR). EEG data were captured, processed, and analyzed to study brain activity patterns related to MDD. The participants were divided based on suicide risk levels, and statistical analyses, including chi-square, t-tests, Pearson’s correlations were used to explore the associations between brain activity, symptom severity, and suicide risk. Closely related variables were identified and ultimately the optimal model was screened using stepwise regression analysis with a forward strategy, and mediation effects were further used to determine the possible interactions between the variables in the regression model.ResultsThe regression model showed a significant effect of HDRS-17 and alpha power of Medial Occipital Cortex (MOC) on suicide risk, with elevated HDRS-17 increasing suicide risk and elevated alpha power decreasing suicide risk. Mediation effect analyses showed that MOC alpha power partially mediated the effect of depression level on suicide risk, and that an increase in depression severity may lead to a decrease in MOC alpha power, while a decrease in MOC alpha power may lead to an increase in suicide risk.ConclusionThe severity of depression directly increases suicide risk, whereas higher alpha power in the MOC serves as a protective factor, reducing this risk. Notably, MOC alpha power not only directly impacts suicide risk but also mediates the effects of both depression severity and anxiety levels on this risk.LimitationsThe relatively small sample size of this study may limit the representativeness of the overall MDD patient population and the detailed analysis of different subgroups. This study did not delve into the relationship between the severity of cognitive symptoms in MDD patients and suicide risk

Alterations in electroencephalographic functional connectivity in individuals with major depressive disorder: a resting-state electroencephalogram study

BackgroundMajor depressive disorder (MDD) is the leading cause of disability among all mental illnesses with increasing prevalence. The diagnosis of MDD is susceptible to interference by several factors, which has led to a trend of exploring objective biomarkers. Electroencephalography (EEG) is a non-invasive procedure that is being gradually applied to detect and diagnose MDD through some features such as functional connectivity (FC).MethodsIn this research, we analyzed the resting-state EEG of patients with MDD and healthy controls (HCs) in both eyes-open (EO) and eyes-closed (EC) conditions. The phase locking value (PLV) method was utilized to explore the connection and synchronization of neuronal activities spatiotemporally between different brain regions. We compared the PLV between participants with MDD and HCs in five frequency bands (theta, 4–8 Hz; alpha, 8–12 Hz; beta1, 12–16 Hz; beta2, 16–24 Hz; and beta3, 24–40 Hz) and further analyzed the correlation between the PLV of connections with significant differences and the severity of depression (via the scores of 17-item Hamilton Depression Rating Scale, HDRS-17).ResultsDuring the EO period, lower PLVs were found in the right temporal-left midline occipital cortex (RT-LMOC; theta, alpha, beta1, and beta2) and posterior parietal-right temporal cortex (PP-RT; beta1 and beta2) in the MDD group compared with the HC group, while PLVs were higher in the MDD group in LT-LMOC (beta2). During the EC period, for the MDD group, lower theta and beta (beta1, beta2, and beta3) PLVs were found in PP-RT, as well as lower theta, alpha, and beta (beta1, beta2, and beta3) PLVs in RT-LMOC. Additionally, in the left midline frontal cortex-right temporal cortex (LMFC-RT) and posterior parietal cortex-right temporal cortex (PP-RMOC), higher PLVs were observed in beta2. There were no significant correlations between PLVs and HDRS-17 scores when connections with significantly different PLVs (all p > 0.05) were checked.ConclusionOur study confirmed the presence of differences in FC between patients with MDD and healthy individuals. Lower PLVs in the connection of the right temporal-left occipital cortex were mostly observed, whereas an increase in PLVs was observed in patients with MDD in the connections of the left temporal with occipital lobe (EO), the circuits of the frontal-temporal lobe, and the parietal-occipital lobe. The trends in FC involved in this study were not correlated with the level of depression.LimitationsThe study was limited due to the lack of further analysis of confounding factors and follow-up data. Future studies with large-sampled and long-term designs are needed to further explore the distinguishable features of EEG FC in individuals with MDD

Measurement of the neutron total cross sections of aluminum at the back-n white neutron source of CSNS

Aluminum and its alloys are widely used in the nuclear industry. Therefore, it is essential to precisely measure and accurately know the neutron total cross section of aluminum in the wider energy region. The measurement is performed by using the transmission method at the Back-n White Neutron Source of CSNS. Two aluminum samples 70 mm in diameter and thicknesses of 40 and 60 mm, respectively, were positioned at 55 m from the neutron source. The transmission detector consisted of a multi-layer fast fission chamber loaded with $$^{235}$$U and $$^{238}$$U, and it was located at the 76-m measurement station. By applying the time-of-flight technique, it was possible to extract the n+$$^{27}$$Al total cross section in a wide energy region, from 1 eV to 20 MeV, after the correction for the double-bunch mode of the CSNS accelerator. The total cross sections obtained with the two Al samples are consistent and the results obtained with the $$^{235}$$U fission cells are in good agreement with that with $$^{238}$$U in the energy range of 1–20 MeV. The uncertainty of neutron total cross section measured with $$^{235}$$U for 40 mm and 60 mm thick aluminum is 0.7–22.3% and 0.6–12.4% in the energy range of 10 keV–20 MeV. Results are in fair agreement with respect to previous data and evaluations

Erratum to: Neutron energy spectrum measurement of the Back-n white neutron source at CSNS

In the original article, there were some errors in the list of authors and affiliations. Their correct version is given in this erratum

Neutron energy spectrum measurement of the Back-n white neutron source at CSNS

China Spallation Neutron Source (CSNS) has been built and commissioned successfully in 2018 which is implemented by impinging 1.6 GeV protons onto a tungsten target with 25 Hz repetition frequency. An associated white neutron beam line exploiting the back-streaming neutrons, named Back-n, with a flight path of 55 m in endstation 1 (#ES1) and 76 m in endstation 2 (#ES2) was built mainly for nuclear data measurements. The Back-n beam line started running since the beginning of 2018 and the neutron energy spectrum was measured at the very beginning since it is an essential information for feasibility study and analysis of any measurement. In this paper, the measurement of the neutron energy spectrum of Back-n #ES2 is reported. The first result of the neutron flux from 1 eV to 100 MeV measured by a fission chamber based on the 235U(n, f) reaction is presented. The total neutron flux normalized to the proton beam power of 100 kW is $7.03 \times 10^{6}$ neutrons/cm2/s. The results show a good agreement with that of the Monte Carlo simulation as well

Measurement of the neutron energy spectrum of Back-n #ES1 at CSNS

The China spallation neutron source (CSNS) was built and started running since 2018. It produces neutrons by impinging 1.6 GeV protons onto a tungsten target with 25 Hz repetition frequency. A beam line exploiting the back-streaming neutrons (Back-n) was built mainly for nuclear data measurement and started commissioning simultaneously with CSNS in 2018. There are two experimental endstations along the Back-n beam line: endstation 1 (#ES1) with a neutron flight path of about 55 m and endstation 2 (#ES2) with about 76 m. The neutron energy spectra of both #ES1 and #ES2 were measured since it is important for feasibility study and analysis. In this paper, the measurement of the neutron energy spectrum of Back-n #ES1 is reported. It is measured by a multi-layer fission chamber using the 235U samples as the neutron converters. The neutron energy spectrum from 0.1 eV to 30 MeV is obtained. The integral neutron flux (from 0.1 eV to 30 MeV) normalized to the proton beam power of 100 kW is 1.55×107 neutrons/cm2/s