Dynamic functional network connectivity based on spatial source phase maps of complex-valued fMRI data: Application to schizophrenia.

BACKGROUND: Dynamic spatial functional network connectivity (dsFNC) has shown advantages in detecting functional alterations impacted by mental disorders using magnitude-only fMRI data. However, complete fMRI data are complex-valued with unique and useful phase information. METHODS: We propose dsFNC of spatial source phase (SSP) maps, derived from complex-valued fMRI data (named SSP-dsFNC), to capture the dynamics elicited by the phase. We compute mutual information for connectivity quantification, employ statistical analysis and Markov chains to assess dynamics, ultimately classifying schizophrenia patients (SZs) and healthy controls (HCs) based on connectivity variance and Markov chain state transitions across windows. RESULTS: SSP-dsFNC yielded greater dynamics and more significant HC-SZ differences, due to the use of complete brain information from complex-valued fMRI data. COMPARISON WITH EXISTING METHODS: Compared with magnitude-dsFNC, SSP-dsFNC detected additional and meaningful connections across windows (e.g., for right frontal parietal) and achieved 14.6% higher accuracy for classifying HCs and SZs. CONCLUSIONS: This work provides new evidence about how SSP-dsFNC could be impacted by schizophrenia, and this information could be used to identify potential imaging biomarkers for psychotic diagnosis.

[Characteristics of Hydrogen and Oxygen Isotopes in Different Water Bodies in Hilly and Gully Regions of the Loess Plateau].

Studying the isotope characteristics and water body transformation relationships among different water bodies in the hilly and gully region of the Loess Plateau can provide a theoretical foundation for evaluating regional climate, ecology, and water resources. In this study, daily and monthly averaged δD and δ18O in precipitation, river water, and shallow groundwater were measured in 2017 in the Jiuyuangou watershed, which has a good ecological condition. The compositional relationship between the stable hydrogen and oxygen isotopes in difference water bodies was explored, the influence factors and spatio-temporal variation of δ18O in precipitation and river water were analyzed, and the stable isotope conversion ratios between different water bodies in the study area were calculated using the two-terminal mixed model. The main conclusions of the study are as follows:the d-excess of river water showed an increasing trend with elevation during the observation period; the δ18O of river water was enriched with increasing distance from the river source and decreased with increasing altitude; temperature, wind speed, and relative humidity had significant effects on the hydrogen and oxygen isotopes of precipitation; precipitation and shallow groundwater replenish the river during the non-flood period, the proportions of which were 46% and 54%, respectively; and during the flood season, the shallow groundwater is replenished by river water and precipitation, the proportions were 60% and 40%, respectively. These results indicate that there is a good conversion relationship between "precipitation-river-shallow groundwater" in the study area. The implementation of soil and water conservation measures has had some influence on the conversion of different water bodies in small watersheds. The results provide a basis for the establishment of water cycle models for hilly and gully regions of the Loess Plateau.