New neuroimaging techniques have led to significant advancements in our understanding of cerebral mechanisms of primary insomnia. However, the neuronal low-frequency oscillation remains largely uncharacterized in chronic primary insomnia (CPI). In this study, the amplitude of low-frequency fluctuation (ALFF), a data-driven method based on resting-state functional MRI, was used to examine local intrinsic activity in 27 patients with CPI and 27 age-, sex-, and education-matched healthy controls. We examined neural activity in two frequency bands, slow-4 (between 0.027 and 0.073 Hz) and slow-5 (0.010-0.027 Hz), because blood-oxygen level dependent (BOLD) fluctuations in different low-frequency bands may present different neurophysiological manifestations that pertain to a spatiotemporal organization. The ALFF associated with the primary disease effect was widely distributed in the cerebellum posterior lobe (CPL), dorsal and ventral prefrontal cortex, anterior cingulate cortex, precuneus, somatosensory cortex, and several default-mode sub-regions. Several brain regions (i.e., the right cerebellum, anterior lobe, and left putamen) exhibited an interaction between the frequency band and patient group. In the slow-5 band, increased ALFF of the right postcentral gyrus/inferior parietal lobule (PoCG/IPL) was enhanced in association with the sleep quality (ρ = 0.414, P = 0.044) and anxiety index (ρ = 0.406, P = 0.049) of the CPI patients. These findings suggest that during chronic insomnia, the intrinsic functional plasticity primarily responds to the hyperarousal state, which is the loss of inhibition in sensory-informational processing. Our findings regarding an abnormal sensory input and intrinsic processing mechanism might provide novel insight into the pathophysiology of CPI. Furthermore, the frequency factor should be taken into consideration when exploring ALFF-related clinical manifestations.

Brain entropy (BEN) mapping provides a novel approach to characterize brain temporal dynamics, a key feature of human brain. Using resting state functional magnetic resonance imaging (rsfMRI), reliable and spatially distributed BEN patterns have been identified in normal brain, suggesting a potential use in clinical populations since temporal brain dynamics and entropy may be altered in disease conditions. The purpose of this study was to characterize BEN in multiple sclerosis (MS), a neurodegenerative disease that affects millions of people. Since currently there is no cure for MS, developing treatment or medication that can slow down its progression represents a high research priority, for which validating a brain marker sensitive to disease and the related functional impairments is essential. Because MS can start long time before any measurable symptoms and structural deficits, assessing the dynamic brain activity and correspondingly BEN may provide a critical way to study MS and its progression. Because BEN is new to MS, we aimed to assess BEN alterations in the relapsing-remitting MS (RRMS) patients using a patient versus control design, to examine the correlation of BEN to clinical measurements, and to check the correlation of BEN to structural brain measures which have been more often used in MS studies. As compared to controls, RRMS patients showed increased BEN in motor areas, executive control area, spatial coordinating area, and memory system. Increased BEN was related to greater disease severity as measured by the expanded disability status scale (EDSS) and greater tissue damage as indicated by the mean diffusivity. Patients also showed decreased BEN in other places, which was associated with less disability or fatigue, indicating a disease-related BEN re-distribution. Our results suggest BEN as a novel and useful tool for characterizing RRMS.

Little is known about the interactions between the default mode network (DMN) subregions in relapsing-remitting multiple sclerosis (RRMS). This study used diffusion tensor imaging (DTI) and resting-state functional MRI (rs-fMRI) to examine alterations of long white matter tracts in paired DMN subregions and their functional connectivity in RRMS patients. Twenty-four RRMS patients and 24 healthy subjects participated in this study. The fiber connections derived from DTI tractography and the temporal correlation coefficient derived from rs-fMRI were combined to examine the inter-subregion structural-functional connectivity (SC-FC) within the DMN and its correlations with clinical markers. Compared with healthy subjects, the RRMS patients showed the following: 1) significantly decreased SC and increased FC in the pair-wise subregions; 2) two significant correlations in SC-FC coupling patterns, including the positive correlation between slightly increased FC value and long white matter tract damage in the PCC/PCUN-MPFC connection, and the negative correlations between significantly increased FC values and long white matter tract damage in the PCC/PCUN-bilateral mTL connections; 3) SC alterations [log(N track) of the PCC/PCUN-left IPL, RD value of the MPFC-left IPL, FA value of the PCC/PCUN-left mTL connections] correlated with EDSS, increases in the RD value of MPFC-left IPL connection was positively correlated to the MFIS; and decreases in the FA value of PCC/PCUN-right IPL connection was negatively correlated with the PASAT; 4) decreased SC (FA value of the MPFC-left IPL, track volume of the PCC/PCUN-MPFC, and log(N track) of PCC/PCUN-left mTL connections) was positively correlated with brain atrophy. In the connections of paired DMN subregions, we observed decreased SC and increased FC in RRMS patients. The relationship between MS-related structural abnormalities and clinical markers suggests that the disruption of this long-distance “inter-subregion” connectivity (white matter) may significantly impact the integrity of the network's function.

Several neuroimaging studies have suggested brain reorganisation in patients with cervical spondylotic myelopathy (CSM); however, the changes in spontaneous neuronal activity that are associated with connectedness remain largely unknown. In this study, functional connectivity strength (FCS), a data-driven degree centrality method based on a theoretical approach, was applied for the first time to investigate changes in the sensory-motor network (SMN) at the voxel level. Comparatively, CSM not only showed significantly decreased FCS in the operculum-integrated regions, which exhibited reduced resting-state functional connectivity (rsFC) around the Rolandic sulcus, but it also showed increased FCS in the premotor, primary somatosensory and parietal-integrated areas, which primarily showed an enhanced rsFC pattern. Correlation analysis showed that altered FCS (in the left premotor-ventral/precentral-operculum, right operculum-parietale 4 and right S1) was associated with worsening Japanese Orthopaedic Association scores and that the rsFC pattern was influenced by cervical cord micro-structural damage at the C2 level. Together, these findings suggest that during myelopathy, the intrinsic functional plasticity of the SMN responds to the insufficient sensory and motor experience in CSM patients. This knowledge may improve our understanding of the comprehensive functional defects found in CSM patients and may inspire the development of new therapeutic strategies in the future.

Objective: The aim of this study was to explore the amplitude of intrinsic low-frequency oscillations (LFOs) in patients with discogenic low-back and leg pain (LBLP). Participants and methods: We obtained and compared the LFO amplitude from 25 right-handed discogenic LBLP patients (13 males; mean age 55.16±1.83 years) and 27 well-matched healthy controls (15 males; mean age 52.96±1.63 years). The LFO amplitude was examined using the voxel-wise amplitude of low-frequency fluctuations (ALFFs), and partial correlation analysis was performed to determine the relationship between the regions with altered ALFF values and clinical parameters in discogenic LBLP patients. Results: Compared with healthy controls, the patients with discogenic LBLP showed a significant increase in ALFF in the affective system of the pain matrix (left anterior cingulate cortex, right anterior insula/frontal operculum, and bilateral orbitofrontal cortex) and information-processing regions (middle occipital/temporal gyrus). In addition, a significant decrease in ALFF was observed in the default mode network (DMN; inferior parietal lobule (IPL) and medial prefrontal cortex [mPFC]) and the processing system of the pain matrix (basal ganglia/thalamus/midbrain, postcentral gyrus [PoCG], and fusiform gyrus). Several regions with altered ALFF were associated with disease duration, visual analog scale scores, Barthel index, and fine sensory modality measurements (two-point tactile discrimination of the left and/or right leg). Further operating characteristic curves analysis suggested that the mean ALFF values in the right IPL, left IPL/PoCG, left anterior cingulate cortex, and left mPFC could serve as markers to separate individuals with discogenic LBLP from healthy subjects. Conclusion: Our results revealed widespread abnormalities in ALFF in the pain matrix and information-processing regions as well as a decrease in ALFF in the DMN. These results open up an important new avenue to better understand the nature of the link between intrinsic activity and peripheral pain and sensory impairment in discogenic LBLP patients.

Resting-state functional MRI provides a viable tool for assessing brain dysfunctions in amyotrophic lateral sclerosis (ALS) without using explicit tasks. Altered resting brain functional connectivity (FC) in ALS has been reported in several studies but with large discrepancies in terms of the alteration directions. The purpose of this study was to provide new evidence for the resting FC disruptions in ALS. We focused on FC in the motor network as motor dysfunctions are a hallmark of ALS pathology. To test the hypothesis that ALS is associated with intermotor network FC changes, we compared FC of the key nodes of motor network between 12 ALS patients and 12 matched controls, and found both decreased and increased within-motor network FC in ALS patients. Increased FC between the bilateral superior parietal lobule and the right anterior inferior cerebellum was found to be correlated with disease severity, with higher FC related to more severe disease. The decreased motor network FC may be a result of motor function degradation in ALS, whereas the increased FC and its correlation to disease severity might suggest a brain mechanism to compensate the loss of the normal motor functionality in ALS. Our results also showed that the within-motor cortex FC except the within premotor area FC did not change in these early disease stage patients.