Results of the different PCGC algorithms on simulated data (k = 20). Left: pairwise GC, center: PCGC<i>^d</i>, right: PCGC<i>^t</i>.

<p>Results of the different PCGC algorithms on simulated data (k = 20). Left: pairwise GC, center: PCGC<i>^d</i>, right: PCGC<i>^t</i>.</p

The spatial distribution of hub voxels in a graph binarized with a threshold .

<p>The first row illustrates the spatial distribution of global functional connectivity density hubs. The second (third) row indicates the DC incoming (outgoing) network hubs. The last row indicates the regions which are DC hubs both for FC and EC (incoming/outgoing) networks.</p

Reproducibility of the causal flow from mPFC (purple sphere) when using pairwise GC(left) and PCGC<i>^t</i> (right) under .

<p>Relative frequency with which a voxel was selected as a hub for outgoing information.</p

Visualization of the group-level voxel-wise directed graph.

<p>Upper panel: layout at a sparse 2.4% connection density, 8156 voxels with degree>11 are displayed; the 17 bigger communities (detected from the directed network at group level) are indicated by different colors. Lower panel: the spatial distributions of the voxels in the upper panel are mapped on the anatomical image with the same colors.</p

The functional connectome: layout and communities.

<p>The full brain contains about 43413 3-mm cubic voxels for AAL-90 (A), AAL-512(B) and AAL-0124 (C) template. On average 6 functional communities were found. They are colored distinctly within multiple axial slices and 3D rendered on MNI152 standard brain surface (Bottom). To highlight the overall layout at a sparse 2% connection density, the functional connectome was further visualized as a network layout with the same colors (Top).</p

Treatment effects of olanzapine on homotopic connectivity in drug-free schizophrenia at rest

<p><b>Objectives:</b> Deficits in homotopic connectivity have been implicated in schizophrenia. However, alterations in homotopic connectivity associated with antipsychotic treatments in schizophrenia remain unclear due to lack of longitudinal studies.</p> <p><b>Methods:</b> Seventeen drug-free patients with recurrent schizophrenia and 24 healthy controls underwent resting-state functional magnetic resonance imaging scans. The patients were scanned at three time points (baseline, at 6 weeks of treatment, and at 6 months of treatment). Voxel-mirrored homotopic connectivity (VMHC) was applied to analyse the imaging data to examine alterations in VMHC associated with antipsychotic treatment.</p> <p><b>Results:</b> The results showed that patients with schizophrenia exhibited decreased VMHC in the default-mode network (such as the precuneus and inferior parietal lobule) and the motor and sensory processing regions (such as the lingual gyrus, fusiform gyrus and cerebellum lobule VI), which could be normalised or denormalised by olanzapine treatment. In addition, negative correlations were found between decreased VMHC and symptom severity in the patients at baseline.</p> <p><b>Conclusions:</b> The present study shows that olanzapine treatment can normalise or denormalise decreased homotopic connectivity in schizophrenia. The findings also provide a new perspective to understand treatment effects of antipsychotic drugs on homotopic connectivity in schizophrenia that contribute to the disconnection hypothesis of this disease.</p

The DMN mask determined by ICA from the control group and statistical maps showing NH differences between subject groups.

<p>Red and blue denote higher and lower NH, respectively. Colored bars indicate the <i>T</i> value from two-sample <i>t</i>-tests. DMN = default mode network; ICA = independent component analysis; NH = network homogeneity.</p

Aberrant Functional Connectivity of Resting State Networks in Transient Ischemic Attack

<div><p>Background</p><p>Transient ischemic attack (TIA) is usually defined as a neurologic ischemic disorder without permanent cerebral infarction. Studies have showed that patients with TIA can have lasting cognitive functional impairment. Inherent brain activity in the resting state is spatially organized in a set of specific coherent patterns named resting state networks (RSNs), which epitomize the functional architecture of memory, language, attention, visual, auditory and somato-motor networks. Here, we aimed to detect differences in RSNs between TIA patients and healthy controls (HCs).</p><p>Methods</p><p>Twenty one TIA patients suffered an ischemic event and 21 matched HCs were enrolled in the study. All subjects were investigated using cognitive tests, psychiatric tests and functional magnetic resonance imaging (fMRI). Independent component analysis (ICA) was adopted to acquire the eight brain RSNs. Then one-sample t-tests were calculated in each group to gather the spatial maps of each RSNs, followed by second level analysis to investigate statistical differences on RSNs between twenty one TIA patients and 21 controls. Furthermore, a correlation analysis was performed to explore the relationship between functional connectivity (FC) and cognitive and psychiatric scales in TIA group.</p><p>Results</p><p>Compared with the controls, TIA patients exhibited both decreased and increased functional connectivity in default mode network (DMN) and self-referential network (SRN), and decreased functional connectivity in dorsal attention network (DAN), central-executive network (CEN), core network (CN), somato-motor network (SMN), visual network (VN) and auditory network (AN). There was no correlation between neuropsychological scores and functional connectivity in regions of RSNs.</p><p>Conclusions</p><p>We observed selective impairments of RSN intrinsic FC in TIA patients, whose all eight RSNs had aberrant functional connectivity. These changes indicate that TIA is a disease with widely abnormal brain networks. Our results might put forward a novel way to look into neuro-pathophysiological mechanisms in TIA patients.</p></div

Decreased Interhemispheric Coordination in Treatment-Resistant Depression: A Resting-State fMRI Study

<div><p>Background</p><p>Previous studies have demonstrated that patients with treatment-resistant depression (TRD) and treatment-sensitive depression (TSD) differed at neural level. However, it remains unclear if these two subtypes of depression differ in the interhemispheric coordination. This study was undertaken for two purposes: (1) to explore the differences in interhemispheric coordination between these two subtypes by using the voxel-mirrored homotopic connectivity (VMHC) method; and (2) to determine if the difference of interhemispheric coordination can be used as a biomarker(s) to differentiate TRD from both TSD and healthy subjects (HS).</p><p>Methods</p><p>Twenty-three patients with TRD, 22 with TSD, and 19 HS participated in the study. Data of these participants were analyzed with the VMHC and seed-based functional connectivity (FC) approaches.</p><p>Results</p><p>Compared to the TSD group, the TRD group showed significantly lower VMHC values in the calcarine cortex, fusiform gyrus, hippocampus, superior temporal gyrus, middle cingulum, and precentral gyrus. Lower VMHC values were also observed in the TRD group in the calcarine cortex relative to the HS group. However, the TSD group had no significant change in VMHC value in any brain region compared to the HS group. Receiver operating characteristic curves (ROC) analysis revealed that the VMHC values in the calcarine cortex had discriminatory function distinguishing patients with TRD from patients with TSD as well as those participants in the HS group.</p><p>Conclusions</p><p>Lower VMHC values of patients with TRD relative to those with TSD and those in the HS group in the calcarine cortex appeared to be a unique feature for patients with TRD and it may be used as an imaging biomarker to separate patients with TRD from those with TSD or HS.</p></div

Receiver operating characteristic (ROC) curves using the mean NH in the left dorsal MPFC and the right ITG to separate the patients from healthy controls.

<p>NH = network homogeneity; MPFC = medial prefrontal cortex; ITG = inferior temporal gyrus.</p