The hierarchical organization of the precuneus captured by functional gradients.

The precuneus shows considerable heterogeneity in multiple dimensions including anatomy, function, and involvement in brain disorders. Leveraging the state-of-the-art functional gradient approach, we aimed to investigate the hierarchical organization of the precuneus, which may hold promise for a unified understanding of precuneus heterogeneity. Resting-state functional MRI data from 793 healthy individuals were used to discover and validate functional gradients of the precuneus, which were calculated based on the voxel-wise precuneus-to-cerebrum functional connectivity patterns. Then, we further explored the potential relationships of the precuneus functional gradients with cortical morphology, intrinsic geometry, canonical functional networks, and behavioral domains. We found that the precuneus principal and secondary gradients showed dorsoanterior-ventral and ventroposterior-dorsal organizations, respectively. Concurrently, the principal gradient was associated with cortical morphology, and both the principal and secondary gradients showed geometric distance dependence. Importantly, precuneus functional subdivisions corresponding to canonical functional networks (behavioral domains) were distributed along both gradients in a hierarchical manner, i.e., from the sensorimotor network (somatic movement and sensation) at one extreme to the default mode network (abstract cognitive functions) at the other extreme for the principal gradient and from the visual network (vision) at one end to the dorsal attention network (top-down control of attention) at the other end for the secondary gradient. These findings suggest that the precuneus functional gradients may provide mechanistic insights into the multifaceted nature of precuneus heterogeneity.

Functional connectivity gradients of the cingulate cortex.

Heterogeneity of the cingulate cortex is evident in multiple dimensions including anatomy, function, connectivity, and involvement in networks and diseases. Using the recently developed functional connectivity gradient approach and resting-state functional MRI data, we found three functional connectivity gradients that captured distinct dimensions of cingulate hierarchical organization. The principal gradient exhibited a radiating organization with transitions from the middle toward both anterior and posterior parts of the cingulate cortex and was related to canonical functional networks and corresponding behavioral domains. The second gradient showed an anterior-posterior axis across the cingulate cortex and had prominent geometric distance dependence. The third gradient displayed a marked differentiation of subgenual and caudal middle with other parts of the cingulate cortex and was associated with cortical morphology. Aside from providing an updated framework for understanding the multifaceted nature of cingulate heterogeneity, the observed hierarchical organization of the cingulate cortex may constitute a novel research agenda with potential applications in basic and clinical neuroscience.

Genetic mechanisms underlying brain functional homotopy: a combined transcriptome and resting-state functional MRI study.

Functional homotopy, the high degree of spontaneous activity synchrony and functional coactivation between geometrically corresponding interhemispheric regions, is a fundamental characteristic of the intrinsic functional architecture of the brain. However, little is known about the genetic mechanisms underlying functional homotopy. Resting-state functional magnetic resonance imaging data from a discovery dataset (656 healthy subjects) and 2 independent cross-race, cross-scanner validation datasets (103 and 329 healthy subjects) were used to calculate voxel-mirrored homotopic connectivity (VMHC) indexing brain functional homotopy. In combination with the Allen Human Brain Atlas, transcriptome-neuroimaging spatial correlation analysis was conducted to identify genes linked to VMHC. We found 1,001 genes whose expression measures were spatially associated with VMHC. Functional enrichment analyses demonstrated that these VMHC-related genes were enriched for biological functions including protein kinase activity, ion channel regulation, and synaptic function as well as many neuropsychiatric disorders. Concurrently, specific expression analyses showed that these genes were specifically expressed in the brain tissue, in neurons and immune cells, and during nearly all developmental periods. In addition, the VMHC-associated genes were linked to multiple behavioral domains, including vision, execution, and attention. Our findings suggest that interhemispheric communication and coordination involve a complex interaction of polygenes with a rich range of functional features.

Assessing diagnostic value of contrast-enhanced ultrasound and contrast-enhanced computed tomography in detecting small hepatocellular carcinoma: A meta-analysis.

BACKGROUND: This study aimed to compare the diagnostic values of contrast-enhanced ultrasound (CEUS) and contrast-enhanced computed tomography (CECT) in detecting small hepatocellular carcinoma (SHCC). METHODS: A series of related articles from 2001 to 2015 were searched in PubMed and Embase databases. Data from selected articles were pooled to analyze the sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR), and summary receiver operating characteristic (SROC) curve using Meta-DiSc software. Heterogeneity was estimated using χ-based Cochran-Q test and I-statistics, and publication bias was estimated using Egger test in Stata software. RESULTS: In total, 8 high-quality articles based on 623 subjects including 318 SHCC cases were included. For the extracted data, no heterogeneity and publication bias were observed among these studies. The following respective data on CEUS and CECT were pooled: sensitivities: 0.75 (95% confidence interval [CI]: 0.70-0.80) and 0.74 (95% CI: 0.68-0.78); specificity: 0.91 (95% CI: 0.87-0.94) and 0.92 (95% CI: 0.89-0.95); PLRs: 5.99 (95%CI: 3.28-10.92) and 7.76 (95% CI: 3.12-19.28); NLRs: 0.31 (95% CI: 0.20-0.49) and 0.32 (95% CI: 0.20-0.50); DORs: 27.38 (95% CI: 14.38-52.11) and 30.02 (95% CI: 9.32-96.62). Area under the SROC curve: 0.91 and 0.89 and no significant statistical result was identified between them (Z = 0.23, P = .82). CONCLUSION: CEUS showed a diagnostic ability comparable to that of CECT in detecting SHCC.