Interhemispheric Resting-state Functional Connectivity Research Articles

Brain-Hand Function Relationships Based on Level of Grasp Function in Chronic Left-Hemisphere Stroke

Background and Objective The biomarkers of hand function may differ based on level of motor impairment after stroke. The objective of this study was to determine the relationship between resting state functional connectivity (RsFC) and unimanual contralesional hand function after stroke and whether brain-behavior relationships differ based on level of grasp function. Methods Sixty-two individuals with chronic, left-hemisphere stroke were separated into three functional levels based on Box and Blocks Test performance with the contralesional hand: Low (moved 0 blocks), Moderate (moved >0% but <90% of blocks relative to the ipsilesional hand), and High (moved ≥90% of blocks relative to the ipsilesional hand). Results RsFC in the ipsilesional and interhemispheric motor networks was reduced in the Low group compared to the Moderate and High groups. While interhemispheric RsFC correlated with hand function (grip strength and Stroke Impact Scale Hand) across the sample, contralesional RsFC correlated with hand function in the Low group and no measures of connectivity correlated with hand function in the Moderate and High groups. Linear regression modeling found that contralesional RsFC significantly predicted hand function in the Low group, while no measure correlated with hand function in the High group. Corticospinal tract integrity was the only predictor of hand function for the Moderate group and in an analysis across the entire sample. Conclusions Differences in brain-hand function relationships based on level of motor impairment may have implications for predictive models of treatment response and the development of intervention protocols aimed at improving hand function after stroke.

Parkinson's disease patients show delayed hemodynamic changes in primary motor cortex in fine motor tasks and decreased resting-state interhemispheric functional connectivity: a functional near-infrared spectroscopy study.

People with Parkinson's disease (PD) experience changes in fine motor skills, which is viewed as one of the hallmark signs of this disease. Due to its non-invasive nature and portability, functional near-infrared spectroscopy (fNIRS) is a promising tool for assessing changes related to fine motor skills. We aim to compare activation patterns in the primary motor cortex using fNIRS, comparing volunteers with PD and sex- and age-matched control participants during a fine motor task and walking. Moreover, inter and intrahemispheric functional connectivity (FC) was investigated during the resting state. We used fNIRS to measure the hemodynamic changes in the primary motor cortex elicited by a finger-tapping task in 20 PD patients and 20 controls matched for age, sex, education, and body mass index. In addition, a two-minute walking task was carried out. Resting-state FC was also assessed. Patients with PD showed delayed hypoactivation in the motor cortex during the fine motor task with the dominant hand and delayed hyperactivation with the non-dominant hand. The findings also revealed significant correlations among various measures of hemodynamic activity in the motor cortex using fNIRS and different cognitive and clinical variables. There were no significant differences between patients with PD and controls during the walking task. However, there were significant differences in interhemispheric connectivity between PD patients and control participants, with a statistically significant decrease in PD patients compared with control participants. Decreased interhemispheric FC and delayed activity in the primary motor cortex elicited by a fine motor task may one day serve as one of the many potential neuroimaging biomarkers for diagnosing PD.

Functional connectivity interacts with visual perceptual learning for visual field recovery in chronic stroke

A reciprocal relationship between perceptual learning and functional brain changes towards perceptual learning effectiveness has been demonstrated previously; however, the underlying neural correlates remain unclear. Further, visual perceptual learning (VPL) is implicated in visual field defect (VFD) recovery following chronic stroke. We investigated resting-state functional connectivity (RSFC) in the visual cortices associated with mean total deviation (MTD) scores for VPL-induced VFD recovery in chronic stroke. Patients with VFD due to chronic ischemic stroke in the visual cortex received 24 VPL training sessions over 2 months, which is a dual discrimination task of orientation and letters. At baseline and two months later, the RSFC in the ipsilesional, interhemispheric, and contralesional visual cortices and MTD scores in the affected hemi-field were assessed. Interhemispheric visual RSFC at baseline showed the strongest correlation with MTD scores post-2-month VPL training. Notably, only the subgroup with high baseline interhemispheric visual RSFC showed significant VFD improvement following the VPL training. The interactions between the interhemispheric visual RSFC at baseline and VPL led to improvement in MTD scores and largely influenced the degree of VFD recovery. The interhemispheric visual RSFC at baseline could be a promising brain biomarker for the effectiveness of VPL-induced VFD recovery.

Alterations in Resting-State Interhemispheric Coordination With Refractory Auditory Verbal Hallucinations in Schizophrenia.

The purpose of this study was to investigate resting-state interhemispheric functional connectivity in patients with schizophrenia and refractory auditory verbal hallucinations (RAVHs) by using voxel-mirrored homotopic connectivity (VMHC). Thirty-four patients with schizophrenia and RAVHs (RAVH group), 23 patients with schizophrenia but no auditory verbal hallucinations (non-AVH group), and 28 matched healthy volunteers (healthy control group) were recruited in China. VMHC analyses were used to identify brain areas with significant differences in functional connectivity among the three groups, and correlations between symptom scores and neurological measures were examined. VMHC analyses showed aberrant bilateral connectivity between several homotopic brain regions: the RAVH and non-AVH groups showed differences in bilateral connectivity of the superior and middle temporal gyri, and the RAVH and healthy control groups showed differences in bilateral connectivity of the gyrus rectus, inferior frontal gyrus, and putamen. In addition, interhemispheric connectivity of the superior and middle temporal gyri correlated with patients' positive symptom scores. These findings may help to elucidate the pathophysiological mechanisms underlying auditory verbal hallucinations. The results revealed interhemispheric functional dysconnectivity among patients with schizophrenia and suggest that the dysconnectivity of homotopic brain regions may play an important role in the development of auditory verbal hallucinations.

Enhanced interhemispheric resting-state functional connectivity of the visual network is an early treatment response of paroxetine in patients with panic disorder.

This study aimed to detect alterations in interhemispheric interactions in patients with panic disorder (PD), determine whether such alterations could serve as biomarkers for the diagnosis and prediction of therapeutic outcomes, and map dynamic changes in interhemispheric interactions in patients with PD after treatment. Fifty-four patients with PD and 54 healthy controls (HCs) were enrolled in this study. All participants underwent clinical assessment and a resting-state functional magnetic resonance imaging scan at (i) baseline and (ii) after paroxetine treatment for 4weeks. A voxel-mirrored homotopic connectivity (VMHC) indicator, support vector machine (SVM), and support vector regression (SVR) were used in this study. Patients with PD showed reduced VMHC in the fusiform, middle temporal/occipital, and postcentral/precentral gyri, relative to those of HCs. After treatment, the patients exhibited enhanced VMHC in the lingual gyrus, relative to the baseline data. The VMHC of the fusiform and postcentral/precentral gyri contributed most to the classification (accuracy = 87.04%). The predicted changes were accessed from the SVR using the aberrant VMHC as features. Positive correlations (p < 0.001) were indicated between the actual and predicted changes in the severity of anxiety. These findings suggest that impaired interhemispheric coordination in the cognitive-sensory network characterized PD and that VMHC can serve as biomarkers and predictors of the efficiency of PD treatment. Enhanced VMHC in the lingual gyrus of patients with PD after treatment implied that pharmacotherapy recruited the visual network in the early stages.

Increased resting-state interhemispheric functional connectivity of striatum in first-episode drug-naive adolescent-onset schizophrenia.

Compared to adult-onset schizophrenia, relatively few neuroimaging studies have examined functional connectivity (FC) abnormalities in adolescent-onset schizophrenia (AOS). The present study was designed to investigate resting-state interhemispheric connectivity patterns among drug-naive first-episode AOS patients and potential changes following short-term antipsychotic drug treatment. This study included 107 drug-naïve, first-episode AOS patients (age: 15.33±1.62, 45 males) and 67 matched healthy controls (age: 15.43±1.86, 30 males). All participants underwent resting-state functional magnetic resonance imaging (rs-fMRI) scans, and 34 AOS patients (age: 15.12±1.68, 12 males) also underwent a follow-up scan after 8 weeks of antipsychotic drug treatment. Interhemispheric functional connectivity was measured by voxel-mirrored homotopic connectivity (VMHC). Compared to healthy controls, AOS patients showed increased VMHC values in putamen and caudate. No significant differences were observed between the patients at baseline and after 8 weeks of treatment. First-episode, drug-naive AOS patients demonstrate abnormalities in interhemispheric FC, and these are not mitigated by short-term antipsychotic treatment.

Motor inhibition and its contribution to recovery of dexterous hand use after stroke.

Recovery of dexterous hand use is critical for functional outcome after stroke. Grip force recordings can inform on maximal motor output and modulatory and inhibitory cerebral functions, but how these actually contribute to recovery of dexterous hand use is unclear. This cohort study used serially assessed measures of hand kinetics to test the hypothesis that behavioural measures of motor modulation and inhibition explain dexterity recovery beyond that explained by measures of motor output alone. We also investigated the structural and functional connectivity correlates of grip force control recovery.Eighty-nine adults (median age = 54 years, 26% females) with first-ever ischaemic or haemorrhagic stroke and persistent arm and hand paresis were assessed longitudinally, at 3 weeks, and at 3 and 6 months after stroke. Kinetic measures included: maximal grip force, accuracy of precision and power grip force control, and ability to release force abruptly. Dexterous hand use was assessed clinically with the Box and Block Test and motor impairment with the upper extremity Fugl-Meyer Assessment. Structural and functional MRI was used to assess weighted corticospinal tract lesion load, voxel-based lesion symptom mapping and interhemispheric resting-state functional connectivity.Fifty-three per cent of patients had severe initial motor impairment and a majority still had residual force control impairments at 6 months. Force release at 3 weeks explained 11% additional variance of Box and Block Test outcome at 6 months, above that explained by initial scores (67%). Other kinetic measures did not explain additional variance of recovery. The predictive value of force release remained significant when controlling for corticospinal tract lesion load and clinical measures. Corticospinal tract lesion load correlated with recovery in grip force control measures. Lesions involving the parietal operculum, insular cortex, putamen and fronto-striatal tracts were also related to poorer force modulation and release. Lesions to fronto-striatal tracts explained an additional 5% of variance in force release beyond the 43% explained by corticospinal injury alone. Interhemispheric functional connectivity did not relate to force control recovery.We conclude that not only voluntary force generation but also force release (reflecting motor inhibition) are important for recovery of dexterous hand use after stroke. Although corticospinal injury is a main determinant of recovery, lesions to integrative somatosensory areas and fronto-parietal white matter (involved in motor inhibition) explain additional variance in post-stroke force release recovery. Our findings indicate that post-stroke upper limb motor impairment profiling, which is essential for targeted treatment, should consider both voluntary grasp generation and inhibition.

Disrupted interhemispheric functional connectivity in primary angle-closure glaucoma: a functional MRI study: voxel-mirrored homotopic connectivity in primary angle-closure glaucoma patients.

The purpose of the study is to use the voxel-mirrored homotopic connectivity (VMHC) technique to explore the pattern of the interhemispheric functional connectivity in patients with primary angle-closure glaucoma (PACG). The interhemispheric functional connectivity was compared between 31 individuals with PACG and 31 healthy controls closely matched with sex, age, and educational level using the VMHC technique. Significant differences in VMHC between two groups were selected to be classification features for classifying individuals with PACG from healthy controls using the support vector machine algorithm of the machine learning. We used the permutation test analysis to assess the classification performance. In addition, the Pearson analysis was applied to explore the relationship between changed VMHC and clinical varieties in patients with PACG. Compared with healthy controls, individuals with PACG exhibited significantly lower VMHC signal values in the right calcarine, right cuneus, right superior occipital gyrus, and right postcentral gyrus [voxel level: P < 0.001, Gaussian random field correction, cluster level: P < 0.05]. Moreover, the results displayed that the total accuracy, sensitivity, and specificity of the machine learning classification were 0.758, 0.710, and 0.807, respectively (P < 0.001, nonparametric permutation test). The findings demonstrated that there is disturbed interhemispheric resting-state functional connectivity in the vision-related brain areas of individuals with PACG; and the VMHC variability can classify individuals with PACG from healthy controls with high accuracy, which provided novel evidence for understanding the neuropathological mechanism of PACG.

Rho-Kinase Inhibition Improves the Outcome of Focal Subcortical White Matter Lesions.

Subcortical white matter lesions are exceedingly common in cerebral small vessel disease and lead to significant cumulative disability without an available treatment. Here, we tested a rho-kinase inhibitor on functional recovery after focal white matter injury. A focal corpus callosum lesion was induced by stereotactic injection of N5-(1-iminoethyl)-L-ornithine in mice. Fasudil (10 mg/kg) or vehicle was administered daily for 2 weeks, starting one day after lesion induction. Resting-state functional connectivity and grid walk performance were studied longitudinally, and lesion volumes were determined at one month. Resting-state interhemispheric functional connectivity significantly recovered between days 1 and 14 in the fasudil group (P<0.001), despite worse initial connectivity loss than vehicle before treatment onset. Grid walk test revealed an increased number of foot faults in the vehicle group compared with baseline, which persisted for at least 4 weeks. In contrast, the fasudil arm did not show an increase in foot faults and had smaller lesions at 4 weeks. Immunohistochemical examination of reactive astrocytosis, synaptic density, and mature oligodendrocytes did not reveal a significant difference between treatment arms. These data show that delayed fasudil posttreatment improves functional outcomes after a focal subcortical white matter lesion in mice. Future work will aim to elucidate the mechanisms.

Impaired Interhemispheric Synchrony in Parkinson's Disease with Fatigue.

The characteristics of interhemispheric resting-state functional connectivity (FC) in Parkinson’s disease (PD) with fatigue remain unclear; therefore, we aimed to explore the changes in interhemispheric FC in PD patients with fatigue. Sixteen PD patients with fatigue (PDF), 16 PD patients without fatigue (PDNF) and 15 matched healthy controls (HCs) were enrolled in the retrospective cross-sectional study. We used voxel-mirrored homotopic connectivity (VMHC) to analyze the resting-state functional magnetic resonance imaging (fMRI) data of these subjects. Compared to PDNF, PDF patients had decreased VMHC values in the supramarginal gyri (SMG). Furthermore, the mean VMHC values of the SMG were negatively correlated with the mean fatigue severity scale (FSS/9) scores (r = −0.754, p = 0.001). Compared to HCs, PDF patients had decreased VMHC in the SMG and in the opercular parts of the inferior frontal gyri (IFG operc). The VMHC values in the IFG operc and middle frontal gyri (MFG) were notably decreased in PDNF patients compared with HCs. Our findings suggest that the reduced VMHC values within the bilateral SMG may be the unique imaging features of fatigue in PD, and may illuminate the neural mechanisms of fatigue in PD.

Aberrant resting-state interhemispheric functional connectivity in patients with anti-N-methyl-D-aspartate receptor encephalitis.

Previous studies have discovered different neuroimaging features in anti-NMDAR encephalitis associated with cognitive dysfunction. However, it is unknown whether there is a correlation between abnormal homotopic connectivity and cognitive impairment in anti-NMDAR encephalitis. We aim to explore the homotopic connectivity patterns of patients with anti-NMDAR encephalitis and their associations with clinical characteristics. Resting-state functional magnetic resonance imaging (rs-fMRI) was performed on 29 patients with anti-NMDAR encephalitis and 26 healthy controls (HCs). Voxel-mirrored homotopic connectivity (VMHC) and multivariate pattern analysis (MVPA) were applied to analyze the imaging data. A correlation was also performed between aberrant brain regions and clinical parameters. Compared to HCs, the performance of alertness in the patient group was typically worse (p < 0.05). A significant decrease in VMHC was observed in many regions of the patients in comparison to HCs, including the cerebellar 6, para-hippocampal gyrus, insula, precuneus, and middle frontal gyrus (p < 0.001). The insula and middle frontal gyrus were found to show positive correlations with alertness. The MVPA method achieved a classification accuracy of 74.55% with a sensitivity of 82.76% and a specificity of 65.38% in discriminating patients from HCs. Our findings indicate that interhemispheric functional imbalance may play a significant role in the pathophysiology of cognitive dysfunction in anti-NMDAR encephalitis. The MVPA results suggest that abnormal VMHC may play a crucial role in the identification of patients with anti-NMDAR encephalitis from HCs.

Dynamic Relationship Between Interhemispheric Functional Connectivity and Corticospinal Tract Changing Pattern After Subcortical Stroke

Background and PurposeIncreased interhemispheric resting-state functional connectivity (rsFC) between the bilateral primary motor cortex (M1) compensates for corticospinal tract (CST) impairment, which facilitates motor recovery in chronic subcortical stroke. However, there is a lack of data on the evolution patterns and correlations between M1–M1 rsFC and diffusion indices of CSTs with different origins after subcortical stroke and their relations with long-term motor outcomes.MethodsA total of 44 patients with subcortical stroke underwent longitudinal structural and functional magnetic resonance imaging (MRI) examinations and clinical assessments at four time points. Diffusion tensor imaging was used to extract fractional anisotropy (FA) values of the affected CSTs with different origins. Resting-state functional MRI was used to calculate the M1–M1 rsFC. Longitudinal patterns of functional and anatomic changes in connections were explored using a linear mixed-effects model. Dynamic relationships between M1–M1 rsFC and FA values of the affected specific CSTs and the impact of these variations on the long-term motor outcomes were analyzed in patients with subcortical stroke.ResultsStroke patients showed a significantly decreased FA in the affected specific CSTs and a gradually increasing M1–M1 rsFC from the acute to the chronic stage. The FA of the affected M1 fiber was negatively correlated with the M1–M1 rsFC from the subacute to the chronic stage, FA of the affected supplementary motor area fiber was negatively correlated with the M1–M1 rsFC in the subacute stage, and FA of the affected M1 fiber in the acute stage was correlated with the long-term motor recovery after subcortical stroke.ConclusionOur findings show that the FA of the affected M1 fiber in the acute stage had the most significant correlation with long-term motor recovery and may be used as an imaging biomarker for predicting motor outcomes after stroke. The compensatory role of the M1–M1 rsFC enhancement may start from the subacute stage in stroke patients with CST impairment.

FV 25 Interhemispheric connectivity of frontoparietal motor regions aids grasping performance after stroke

Introduction: After a stroke, increased neural activation in the contralesional primary motor cortex (M1) and the anterior intraparietal sulcus (aIPS) has been discussed to indicate supporting or disturbing roles for motor function, depending on patients‘ impairment and motor network connectivity (Di Pino et al., 2014). Prior studies have focused on interfering with M1 during the execution of simple motor tasks to test this hypothesis using online-rTMS. However, parietal areas are typically engaged in more demanding tasks. We hence combined task and resting-state fMRI, followed by neuronavigated online-rTMS to assess the roles of M1 and aIPS for complex upper limb movements in relation to interhemispheric resting-state functional connectivity (RSFC) with their ipsilesional counterparts. Methods: Resting fMRI and task fMRI were acquired from 18 chronic stroke patients and 18 age-matched controls. Task-related activation peaks in bilateral aIPS as well as the electrophysiological hotspot in contralesional M1 were identified in each participant and targeted by online-rTMS (10 Hz trains, 90% of resting motor threshold) during (i) index finger-tapping, (ii) reach-to-point, and (iii) reach-to-grasp movements. For sham rTMS, the coil was tilted over the parieto-occipital vertex. We analyzed 3D hand kinematics (smoothness, efficiency, accuracy, speed) in each task and clustered well and poorly recovered patients using K means. Additionally, we extracted performance across all kinematic data by multiple factor analysis. Kinematics during real online rTMS were normalized to the sham condition and correlated with RSFC between bilateral M1, aIPS, and dorsal premotor cortex (dPMC; Rehme et al., 2012). Results: Clustering of kinematics yielded one cluster with healthy controls and recovered patients as opposed to a second cluster with impaired patients. RSFC between bilateral aIPS and between ipsilesional aIPS and dorsal premotor cortex was higher in recovered compared to impaired patients. Interhemispheric connectivity between bilateral M1 and ipsilesional aIPS with contralesional M1 correlated with better motor performance. Online rTMS revealed that patients with increased RSFC between bilateral M1 were impaired in grasping speed when interfering with contralesional M1, whereas patients with increased RSFC between bilateral aIPS deteriorated in grasping accuracy when interfering with contralesional aIPS. Conclusion: The present findings suggest a link between stroke impairment and interhemispheric RSFC between bilateral M1 and aIPS. Interfering with contralesional M1 and aIPS further showed a supportive role of M1 and aIPS in patients with higher interhemispheric connectivity. This finding may indicate that resources from the contralesional M1 and aIPS are accessed via transcallosal connections, aiding different aspects of complex hand movements in chronic stroke. References Di Pino G et al. Nat Rev Neurol 2014. Rehme AK et al. NeuroImage 2012.

Altered Static and Dynamic Interhemispheric Resting-State Functional Connectivity in Patients With Thyroid-Associated Ophthalmopathy.

Purpose: Thyroid-associated ophthalmopathy (TAO) is a debilitating and sight-threatening autoimmune disease that severely impairs patients’ quality of life. Besides the most common ophthalmic manifestations, the emotional and psychiatric disturbances are also usually observed in clinical settings. This study was to investigate the interhemispheric functional connectivity alterations in TAO patients using resting-state functional magnetic resonance imaging (rs-fMRI).Methods: Twenty-eight TAO patients and 22 healthy controls (HCs) underwent rs-fMRI scans. Static and dynamic voxel-mirrored homotopic connectivity (VMHC) values were calculated and compared between the two groups. A linear support vector machine (SVM) classifier was used to examine the performance of static and dynamic VMHC differences in distinguishing TAOs from HCs.Results: Compared with HCs, TAOs showed decreased static VMHC in lingual gyrus (LG)/calcarine (CAL), middle occipital gyrus, postcentral gyrus, superior parietal lobule, inferior parietal lobule, and precuneus. Meanwhile, TAOs demonstrated increased dynamic VMHC in orbitofrontal cortex (OFC). In TAOs, static VMHC in LG/CAL was positively correlated with visual acuity (r = 0.412, P = 0.036), whilst dynamic VMHC in OFC was positively correlated with Hamilton Anxiety Rating Scale (HARS) score (r = 0.397, P = 0.044) and Hamilton Depression Rating Scale (HDRS) score (r = 0.401, P = 0.042). The SVM model showed good performance in distinguishing TAOs from HCs (area under the curve, 0.971; average accuracy, 94%).Conclusion: TAO patients had altered static and dynamic VMHC in the occipital, parietal, and orbitofrontal areas, which could serve as neuroimaging prediction markers of TAO.

Disrupted resting-state interhemispheric functional connectivity in systemic lupus erythematosus patients with and without neuropsychiatric lupus.

The aim of the study is to explore interhemispheric homotopic functional connectivity alterations in systemic lupus erythematosus (SLE) patients with and without neuropsychiatric lupus (NPSLE and non-NPSLE, respectively) and their potential correlations with clinical characteristics and neuropsychological performance. Based on resting-state functional MRI (rs-fMRI) data collected from SLE patients and matched healthy controls (HCs), the voxel-mirrored homotopic connectivity (VMHC) analysis was conducted to measure functional homotopy. Subsequently, correlations between altered functional homotopy and clinical/neuropsychological data were analyzed. Compared with the HC group, both NPSLE and non-NPSLE groups showed attenuated homotopic connectivity in middle temporal gyrus (MTG), cuneus (CUN), middle occipital gyrus (MOG), angular gyrus (ANG), and postcentral gyrus (PoCG). NPSLE patients also exhibited decreased homotopic connectivity in inferior parietal gyrus (IPG) and middle frontal gyrus (MFG). Compared with non-NPSLE patients, NPSLE patients showed weaker interhemispheric homotopic functional connectivity in MOG. Decreased homotopic functional connectivity in PoCG, IPG, and MOG were associated with the anxiety state of SLE patients. Our findings revealed attenuated functional homotopy in both NPSLE and non-NPSLE groups compared to the HC group, which appeared to be more severe in patients with comorbid neuropsychiatric lupus. Interhemispheric homotopy dysconnectivity may participate in the neuropathology of anxiety symptoms in SLE.

Abnormal interhemispheric resting state functional connectivity in Parkinson\u2019s disease patients with impulse control disorders

Impulse control disorders (ICD) in Parkinson’s disease (PD) might be attributed to misestimate of rewards or the failure to curb inappropriate choices. The mechanisms underlying ICD were reported to involve the lateralization of monoamine network. Our objective was to probe the significant role of lateralization in the pathogenesis of ICD. Twenty-one PD patients with ICD (PD-ICD), thirty-three without ICD (PD-no ICD), and thirty-seven healthy controls (HCs) were recruited and performed T1-weighted, diffusion tensor imaging (DTI) scans and resting state functional magnetic resonance imaging (rs-fMRI). By applying the Voxel-mirrored Homotopic Connectivity (VMHC) and Freesurfer, we evaluated participants’ synchronicity of functional connectivity and structural changes between hemispheres. Also, tract-based spatial statistics (TBSS) was applied to compare fiber tracts differences. Relative to PD-no ICD group, PD-ICD group demonstrated reduced VMHC values in middle frontal gyrus (MFG). Compared to HCs, PD-ICD group mainly showed decreased VMHC values in MFG, middle and superior orbital frontal gyrus (OFG), inferior frontal gyrus (IFG) and caudate, which were related to reward processing and inhibitory control. The severity of impulsivity was negatively correlated with the mean VMHC values of MFG in PD-ICD group. Receiver operating characteristic (ROC) curves analyses uncovered that the mean VMHC values of MFG might be a potential marker identifying PD-ICD patients. However, we found no corresponding asymmetrical alteration in cortical thickness and no significant differences in fractional anisotropy (FA) and mean diffusivity (MD). Our results provided further evidence for asymmetry of functional connectivity in mesolimbic reward and response inhibition network in ICD.

Narrowband Resting-State fNIRS Functional Connectivity in Autism Spectrum Disorder.

Hemispheric asymmetry in the power spectrum of low-frequency spontaneous hemodynamic fluctuations has been previously observed in autism spectrum disorder (ASD). This observation may imply a specific narrow-frequency band in which individuals with ASD could show more significant alteration in resting-state functional connectivity (RSFC). To test this assumption, we evaluated narrowband RSFC at several frequencies for functional near-infrared spectroscopy signals recorded from the bilateral temporal lobes on 25 children with ASD and 22 typically developing (TD) children. In several narrow-frequency bands, we observed altered interhemispheric RSFC in ASD. However, in the band of 0.01–0.02 Hz, more mirrored channel pairs (or cortical sites) showed significantly weaker RSFC in the ASD group. Receiver operating characteristic analysis further demonstrated that RSFC in the narrowband of 0.01–0.02 Hz might have better differentiation ability between the ASD and TD groups. This may indicate that the narrowband RSFC could serve as a characteristic for the prediction of ASD.

Increased Resting-State Interhemispheric Functional Connectivity of Posterior Superior Temporal Gyrus and Posterior Cingulate Cortex in Congenital Amusia.

Interhemispheric connectivity of the two cerebral hemispheres is crucial for a broad repertoire of cognitive functions including music and language. Congenital amusia has been reported as a neurodevelopment disorder characterized by impaired music perception and production. However, little is known about the characteristics of the interhemispheric functional connectivity (FC) in amusia. In the present study, we used a newly developed voxel-mirrored homotopic connectivity (VMHC) method to investigate the interhemispheric FC of the whole brain in amusia at resting-state. Thirty amusics and 29 matched participants underwent a resting-state functional magnetic resonance imaging (fMRI) scanning. An automated VMHC approach was used to analyze the fMRI data. Compared to the control group, amusics showed increased VMHC within the posterior part of the default mode network (DMN) mainly in the posterior superior temporal gyrus (pSTG) and posterior cingulate cortex (PCC). Correlation analyses revealed negative correlations between the VMHC value in pSTG/PCC and the music perception ability among amusics. Further ROC analyses showed that the VMHC value of pSTG/PCC showed a good sensibility/specificity to differentiate the amusics from the controls. These findings provide a new perspective for understanding the neural basis of congenital amusia and imply the immature state of DMN may be a credible neural marker of amusia.

Decreased homotopic interhemispheric functional connectivity in children with autism spectrum disorder.

While several functional and structural changes occur in large-scale brain networks in autism spectrum disorder (ASD), reduced interhemispheric resting-state functional connectivity (rsFC) between homotopic regions may be of particular importance as a biomarker. ASD is an early-onset developmental disorder and neural alterations are often age-dependent. Although there is some evidence for homotopic interhemispheric rsFC alterations in language processing regions in ASD children, wider analyses using large data sets have not been performed. The present study, therefore, conducted a voxel-based homotopic interhemispheric rsFC analysis in 146 ASD and 175 typically developing children under-age 10 and examined associations with symptom severity in the autism brain imaging data exchange data sets. Given the role of corpus callosum (CC) in interhemispheric connectivity and reported CC volume changes in ASD we additionally examined whether there were parallel volumetric changes. Results demonstrated decreased homotopic rsFC in ASD children in the posterior cingulate cortex (PCC) and precuneus of the default mode network, the precentral gyrus of the mirror neuron system, and the caudate of the reward system. Homotopic rsFC of the PCC was associated with symptom severity. Furthermore, although no significant CC volume changes were found in ASD children, there was a significant negative correlation between the anterior CC volumes and homotopic rsFC strengths in the caudate. The present study shows that a reduced pattern of homotopic interhemispheric rsFC in ASD adults/adolescents is already present in children of 5-10 years old and further supports their potential use as a general ASD biomarker. LAY SUMMARY: Homotopic interhemispheric functional connectivity plays an important role in synchronizing activity between the two hemispheres and is altered in adults and adolescents with autism spectrum disorder (ASD). In the present study focused on children with ASD, we have observed a similar pattern of decreased homotopic connectivity, suggesting that alterations in homotopic interhemispheric connectivity may occur early in ASD and be a useful general biomarker across ages.

Reduced Inter-hemispheric Resting State Functional Connectivity and Its Association With Social Deficits in Autism.

Autism spectrum disorder (ASD) is an early onset developmental disorder which persists throughout life and is increasing in prevalence over the last few decades. Given its early onset and variable cognitive and emotional functional impairments, it is generally challenging to assess ASD individuals using task-based behavioral and functional MRI paradigms. Consequently, resting state functional MRI (rs-fMRI) has become a key approach for examining ASD-associated neural alterations and revealed functional alterations in large-scale brain networks relative to typically developing (TD) individuals, particularly those involved in social-cognitive and affective processes. Recent progress suggests that alterations in inter-hemispheric resting state functional connectivity (rsFC) between regions in the 2 brain hemispheres, particularly homotopic ones, may be of great importance. Here we have reviewed neuroimaging studies examining inter-hemispheric rsFC abnormities in ASD and its associations with symptom severity. As an index of inter-hemispheric functional connectivity, we have additionally reviewed previous studies on corpus callosum (CC) volumetric and fiber changes in ASD. There are converging findings on reduced inter-hemispheric (including homotopic) rsFC in large-scale brain networks particularly in posterior hubs of the default mode network, reduced volumes in the anterior and posterior CC, and on decreased FA and increased MD or RD across CC subregions. Associations between the strength of inter-hemispheric rsFC and social impairments in ASD together with their classification performance in distinguishing ASD subjects from TD controls across ages suggest that the strength of inter-hemispheric rsFC may be a more promising biomarker for assisting in ASD diagnosis than abnormalities in either brain wide rsFC or brain structure.