Gender differences in cerebral regional homogeneity of adult healthy volunteers: a resting-state FMRI study

Female Cerebellum Seems Sociable; An iTBS Investigation

The cerebellum has been shown to be engaged in tasks other than motor control, including cognitive and affective functions. Prior neuroimaging studies have documented the role of this area in social cognition and despite these findings, no studies have yet examined the causal relationship between the cerebellum and social cognition. This study aimed to investigate the role of the cerebellum in empathy and theory of mind (ToM) in a randomized, placebo-controlled, double-blind, parallel study. 32 healthy participants were assigned to either a sham or active group. For the active group, an intermittent theta-burst stimulation (iTBS) protocol at 100% of the motor threshold was applied to the cerebellum, while the control group received sham stimulation. An eyes-closed EEG session, the Empathy Quotient (EQ) test, and the Reading the Mind in the Eyes Test (RMET) were administered before and after the iTBS session. The results demonstrated differences in cognitive empathy, ToM, and a decrease in the activity of the default mode network (DMN) between the active and sham groups in females. Females also showed a decrease in the activity of the affective empathy network and connectivity in the DMN. We conclude that cognitive empathy and ToM are associated with cerebellar activity, and due to sex-related differences in the cortical organization of this area which is modulated by sex hormones, the stimulation of the cerebellum in males and females yields different results.

Hodge Laplacian of Brain Networks

The closed loops or cycles in a brain network embeds higher order signal transmission paths, which provide fundamental insights into the functioning of the brain. In this work, we propose an efficient algorithm for systematic identification and modeling of cycles using persistent homology and the Hodge Laplacian. Various statistical inference procedures on cycles are developed. We validate the our methods on simulations and apply to brain networks obtained through the resting state functional magnetic resonance imaging. The computer codes for the Hodge Laplacian are given in https://github.com/laplcebeltrami/hodge.

Sexual Differences in Internet Gaming Disorder (IGD): From Psychological Features to Neuroanatomical Networks

Internet gaming disorder (IGD) has been included in the 2013 Diagnostic and Statistical Manual of Mental Disorders (DSM-5) as a condition in need of further study, and gaming disorder was recognized by the World Health Organization as a mental disorder in the International Classification of Disease (ICD-11) of 2018. IGD has different characteristics in the two sexes and is more prevalent in males than females. However, even if the female gamer population is constantly growing, the majority of available studies analyzed only males, or the data were not analyzed by sex. To better elucidate sex differences in IGD, we selectively reviewed research publications that evaluated IGD separately for males and females collected in approximately one hundred publications over the past 20 years. The available data in this narrative review indicate that IGD is strongly dimorphic by sex for both its psychological features and the involvement of different brain areas. Impulsivity, low self-control, anxiety, emotion dysregulation, and depression are some of the psychological features associated with IGD that show a sex dimorphism. At the same time, IGD and its psychological alterations are strongly correlated to dimorphic functional characteristics in relevant brain areas, as evidenced by fMRI. More research is needed to better understand sex differences in IGD. Animal models could help to elucidate the neurological basis of this disorder.

Effect of Phase-Encoding Direction on Gender Differences: A Resting-State Functional Magnetic Resonance Imaging Study

Aim

Neuroimaging studies have highlighted gender differences in brain functions, but conclusions are not well established. Few studies paid attention to the influence of phase-encoding (PE) direction in echo-planar imaging on gender differences, which is a commonly used technique in functional magnetic resonance imaging (fMRI). A disadvantage of echo-planar images is the geometrical distortion and signal loss due to large susceptibility effects along the PE direction. The present research aimed to clarify how PE direction can affect the outcome of a specific research on gender differences.

Methods

We collected resting-state fMRI using anterior to posterior (AP) and posterior to anterior (PA) directions from 113 healthy participants. We calculated several commonly used indices for spontaneous brain activity including amplitude of low frequency fluctuations (ALFF), fractional ALFF (fALFF), regional homogeneity (ReHo), degree centrality (DC), and functional connectivity (FC) of posterior cingulate cortex for each session, and performed three group comparisons: (i) AP versus PA; (ii) male versus female; (iii) interaction between gender and PE direction.

Results

The estimated indices differed substantially between the two PE directions, and the regions that exhibited differences were roughly similar for all the indices. In addition, we found that multiple brain regions showed gender differences in these estimated indices. Further, we observed an interaction effect between gender and PE direction in the bilateral middle frontal gyrus, right precentral gyrus, right postcentral gyrus, right lingual gyrus, and bilateral cerebellum posterior lobe.

Conclusion

These apparent findings revealed that PE direction can partially influence gender differences in spontaneous brain activity of resting-state fMRI. Therefore, future studies should document the adopted PE direction and appropriate selection of PE direction will be important in future resting-state fMRI studies.

The Changes of Brain Function After Spinal Manipulation Therapy in Patients with Chronic Low Back Pain: A Rest BOLD fMRI Study

OBJECTIVE

To investigate the changes of regional homogeneity (Reho) values before and after spinal manipulative therapy (SMT) in patients with chronic low back pain (CLBP) through rest blood-oxygen-level-dependent functional magnetic resonance imaging (BOLD fMRI).

METHODS

Patients with CLBP (Group 1, n = 20) and healthy control subjects (Group 2, n = 20) were recruited. The fMRI was performed three times in Group 1 before SMT (time point 1, TP1), after the first SMT (time point 2, TP2), after the sixth SMT (time point 3, TP3), and for one time in Group 2, which received no intervention. The clinical scales were finished in Group 1 every time before fMRI was performed. The Reho values were compared among Group 1 at different time points, and between Group 1 and Group 2. The correlation between Reho values with the statistical differences and the clinical scale scores were calculated.

RESULTS

The bilateral precuneus and right mid-frontal gyrus in Group 1 had different Reho values compared with Group 2 at TP1. The Reho values were increased in the left precuneus and decreased in the left superior frontal gyrus in Group 1 at TP2 compared with TP1. The Reho values were increased in the left postcentral gyrus and decreased in the left posterior cingulate cortex and the superior frontal gyrus in Group 1 at TP3 compared with TP1. The ReHo values of the left precuneus in Group 1 at TP1 were negatively correlated with the pain degree at TP1 and TP2 (r = -0.549, -0.453; p = 0.012, 0.045). The Reho values of the middle temporal gyrus in Group 1 at TP3 were negatively correlated with the changes of clinical scale scores between TP3 and TP1 (r = 0.454, 0.559; p = 0.044, 0.01).

CONCLUSION

Patients with CLBP showed abnormal brain function activity, which was altered after SMT. The Reho values of the left precuneus could predict the immediate analgesic effect of SMT.

Gender-related difference in altered fractional amplitude of low-frequency fluctuations after electroacupuncture on primary insomnia patients: A resting-state fMRI study

BACKGROUND

Primary insomnia (PI) is defined as a sleep disorder with no definite cause or inducement. Electroacupuncture, a treatment of inserting needles into specific points on the body surface and applying electrical stimulation, has been proved effective in treating PI with minimal adverse effects. However, the influence of gender difference on the clinical treatment efficacy of electroacupuncture for PI patients remains unclear. Therefore, we designed a clinical trial to compare the clinical treatment efficacy of electroacupuncture for PI patients with different genders. The research on the mechanism of electroacupuncture suggested it could modulate the sleep and wakefulness by activating or deactivating brain regions via a needling/tactile somatosensory specific stimulus. Therefore, we also designed a resting-state functional magnetic resonance imaging (rs-fMRI) study to detect the spontaneous brain activity of PI patients before and after the electroacupuncture treatment.

METHOD

Thirty PI patients were recruited to accept 5-week electroacupuncture treatment on HT-7. Athens Insomnia Scale (AIS) and Pittsburgh sleep quality index (PSQI) questionnaires were used to evaluate the clinical treatment efficacy. Rs-fMRI was employed to observe the spontaneous brain activity in the resting state at the baseline and after 5 weeks of electroacupuncture treatment, which was measured by the fractional amplitude of low-frequency fluctuations (fALFF).

RESULT

The AIS and PSQI scores were significantly decreased both in the female PI group and the male PI group after treatment. The decreased PSQI of female patients was significantly more than that of male patients (p < .05). The gender-related difference in the cerebral response to electroacupuncture was mainly in posterior cingulate and supramarginal gyrus.

CONCLUSION

There is a gender-related difference in the clinical treatment efficacy of electroacupuncture for PI patients, and female patients may benefit more from electroacupuncture. Gender-related differences in the cerebral response to electroacupuncture may be one of the factors affecting clinical treatment efficacy.

Confound Removal and Normalization in Practice: A Neuroimaging Based Sex Prediction Case Study

Machine learning (ML) methods are increasingly being used to predict pathologies and biological traits using neuroimaging data. Here controlling for confounds is essential to get unbiased estimates of generalization performance and to identify the features driving predictions. However, a systematic evaluation of the advantages and disadvantages of available alternatives is lacking. This makes it difficult to compare results across studies and to build deployment quality models. Here, we evaluated two commonly used confound removal schemes–whole data confound regression (WDCR) and cross-validated confound regression (CVCR)–to understand their effectiveness and biases induced in generalization performance estimation. Additionally, we study the interaction of the confound removal schemes with Z-score normalization, a common practice in ML modelling. We applied eight combinations of confound removal schemes and normalization (pipelines) to decode sex from resting-state functional MRI (rfMRI) data while controlling for two confounds, brain size and age. We show that both schemes effectively remove linear univariate and multivariate confounding effects resulting in reduced model performance with CVCR providing better generalization estimates, i.e., closer to out-of-sample performance than WDCR. We found no effect of normalizing before or after confound removal. In the presence of dataset and confound shift, four tested confound removal procedures yielded mixed results, raising new questions. We conclude that CVCR is a better method to control for confounding effects in neuroimaging studies. We believe that our in-depth analyses shed light on choices associated with confound removal and hope that it generates more interest in this problem instrumental to numerous applications.

Estimation of gender-specific connectional brain templates using joint multi-view cortical morphological network integration

The estimation of a connectional brain template (CBT) integrating a population of brain networks while capturing shared and differential connectional patterns across individuals remains unexplored in gender fingerprinting. This paper presents the first study to estimate gender-specific CBTs using multi-view cortical morphological networks (CMNs) estimated from conventional T1-weighted magnetic resonance imaging (MRI). Specifically, each CMN view is derived from a specific cortical attribute (e.g. thickness), encoded in a network quantifying the dissimilarity in morphology between pairs of cortical brain regions. To this aim, we propose Multi-View Clustering and Fusion Network (MVCF-Net), a novel multi-view network fusion method, which can jointly identify consistent and differential clusters of multi-view datasets in order to capture simultaneously similar and distinct connectional traits of samples. Our MVCF-Net method estimates a representative and well-centered CBTs for male and female populations, independently, to eventually identify their fingerprinting regions of interest (ROIs) in four main steps. First, we perform multi-view network clustering model based on manifold optimization which groups CMNs into shared and differential clusters while preserving their alignment across views. Second, for each view, we linearly fuse CMNs belonging to each cluster, producing local CBTs. Third, for each cluster, we non-linearly integrate the local CBTs across views, producing a cluster-specific CBT. Finally, by linearly fusing the cluster-specific centers we estimate a final CBT of the input population. MVCF-Net produced the most centered and representative CBTs for male and female populations and identified the most discriminative ROIs marking gender differences. The most two gender-discriminative ROIs involved the lateral occipital cortex and pars opercularis in the left hemisphere and the middle temporal gyrus and lingual gyrus in the right hemisphere.

Gender Differences Are Encoded Differently in the Structure and Function of the Human Brain Revealed by Multimodal MRI

Despite widely reported gender differences in both brain structure and brain function, very few studies have examined the relationship between the structural differences and the functional differences between genders. Here, different imaging measures including both structural [i.e., gray matter volume (GMV)] and functional [i.e., regional homogeneity (ReHo) and functional connectivity (FC)] measures were employed to detect the gender differences in the human brain based on univariate and multivariate approaches with a sample of 290 healthy adults (155 females). The univariate analyses revealed that gender differences were detected in both structural (i.e., GMV) and functional (ReHo or FC) imaging measures, mainly manifested as greater values in females than in males in regions of the frontal, parietal, occipital lobes and cerebellum. Importantly, there was little overlap between the differences detected in GMV and those detected in ReHo and FC, and their differences between genders were not correlated with each other. The multivariate pattern analyses revealed that each of these measures had discriminative power to successfully distinguish between genders (classification accuracy: 94.3%, 90.73%, and 83.89% for GMV, ReHo, and FC, respectively) and their combination further improved the classification performance (96.6%). Our results suggest that gender differences are encoded in both brain structure and brain function, but in different manners. The finding of different and complementary information contained in structural and functional differences between genders highlights the complex relationship between brain structure and function, which may underlie the complex nature of gender differences in behavior.

Understanding Graph Isomorphism Network for rs-fMRI Functional Connectivity Analysis

Graph neural networks (GNN) rely on graph operations that include neural network training for various graph related tasks. Recently, several attempts have been made to apply the GNNs to functional magnetic resonance image (fMRI) data. Despite recent progresses, a common limitation is its difficulty to explain the classification results in a neuroscientifically explainable way. Here, we develop a framework for analyzing the fMRI data using the Graph Isomorphism Network (GIN), which was recently proposed as a powerful GNN for graph classification. One of the important contributions of this paper is the observation that the GIN is a dual representation of convolutional neural network (CNN) in the graph space where the shift operation is defined using the adjacency matrix. This understanding enables us to exploit CNN-based saliency map techniques for the GNN, which we tailor to the proposed GIN with one-hot encoding, to visualize the important regions of the brain. We validate our proposed framework using large-scale resting-state fMRI (rs-fMRI) data for classifying the sex of the subject based on the graph structure of the brain. The experiment was consistent with our expectation such that the obtained saliency map show high correspondence with previous neuroimaging evidences related to sex differences.

Cognitive Control Network Homogeneity and Executive Functions in Late-Life Depression

BACKGROUND

Late-life depression is characterized by network abnormalities, especially within the cognitive control network. We used alternative functional connectivity approaches, regional homogeneity (ReHo) and network homogeneity, to investigate late-life depression functional homogeneity. We examined the association between cognitive control network homogeneity and executive functions.

METHODS

Resting-state functional magnetic resonance imaging data were analyzed for 33 older adults with depression and 43 healthy control subjects. ReHo was performed as the correlation between each voxel and the 27 neighbor voxels. Network homogeneity was calculated as global brain connectivity restricted to 7 networks. T-maps were generated for group comparisons. We measured cognitive performance and executive functions with the Dementia Rating Scale, Trail-Making Test (A and B), Stroop Color Word Test, and Digit Span Test.

RESULTS

Older adults with depression showed increased ReHo in the bilateral dorsal anterior cingulate cortex (dACC) and the right middle temporal gyrus, with no significant findings for network homogeneity. Hierarchical linear regression models showed that higher ReHo in the dACC predicted better performance on Trail-Making Test B (p < .001; R2 = .49), Digit Span Backward (p < .05; R2 = .23), and Digit Span Total (p < .05; R2 = .23). Used as a seed, the dACC cluster of higher ReHo showed lower functional connectivity with bilateral precuneus.

CONCLUSIONS

Higher ReHo within the dACC and right middle temporal gyrus distinguish older adults with depression from control subjects. The correlations with executive function performance support increased ReHo in the dACC as a meaningful measure of the organization of the cognitive control network and a potential compensatory mechanism. Lower functional connectivity between the dACC and the precuneus in late-life depression suggests that clusters of increased ReHo may be functionally segregated.

A Comparison of Static and Dynamic Functional Connectivities for Identifying Subjects and Biological Sex Using Intrinsic Individual Brain Connectivity

Functional magnetic resonance imaging has revealed correlated activities in brain regions even in the absence of a task. Initial studies assumed this resting-state functional connectivity (FC) to be stationary in nature, but recent studies have modeled these activities as a dynamic network. Dynamic spatiotemporal models better model the brain activities, but are computationally more involved. A comparison of static and dynamic FCs was made to quantitatively study their efficacies in identifying intrinsic individual connectivity patterns using data from the Human Connectome Project. Results show that the intrinsic individual brain connectivity pattern can be used as a 'fingerprint' to distinguish among and identify subjects and is more accurately captured with partial correlation and assuming static FC. It was also seen that the intrinsic individual brain connectivity patterns were invariant over a few months. Additionally, biological sex identification was successfully performed using the intrinsic individual connectivity patterns, and group averages of male and female FC matrices. Edge consistency, edge variability and differential power measures were used to identify the major resting-state networks involved in identifying subjects and their sex.

Alterations in Intra- and Interregional Intrinsic Brain Connectivity Are Differentially Associated with Memory Performance in Amnestic Mild Cognitive Impairment

BACKGROUND

Previous research has separated spatial patterns of intra- and interregional intrinsic brain connectivity, as evaluated by regional homogeneity (ReHo) and functional connectivity (FC), respectively, in prodromal Alzheimer's disease (AD). Moreover, the intra- and interregional intrinsic brain connectivities have been demonstrated to have a significant relationship with each other.

OBJECTIVE

To explore FCs from brain regions which display a difference in ReHo between an amnestic mild cognitive impairment (aMCI) group and healthy controls (HC) and to examine the relationship of intra- and interregional intrinsic brain connectivity to cognitive function in both groups.

METHODS

Thirty-four subjects with aMCI and 38 HC underwent 3T MRI scanning and a battery of neuropsychological tests.

RESULTS

The aMCI group exhibited significantly higher ReHo in the left putamen and lower ReHo in the left inferior temporal gyrus than the HC. Furthermore, both groups showed a distinctive functional connectivity pattern seeded from 2 regions of interest which exhibited significant ReHo differences between the groups. In the HC group, only ReHo exhibited significant associations with memory performance, but in the aMCI group, only FC seeded from the left inferior temporal gyrus showed significant correlations with memory performance.

CONCLUSIONS

By approaching both intra- and interregional intrinsic brain activities in the early stages of AD, the findings of this research provide insights into the early pathogenesis of AD as related to memory performance.

Alterations of brain local functional connectivity in amnestic mild cognitive impairment

Background

Resting-state functional magnetic resonance imaging studies using a regional homogeneity (ReHo) method have reported that amnestic mild cognitive impairment (aMCI) was associated with abnormalities in local functional connectivity. However, their results were not conclusive.

Methods

Seed-based d Mapping was used to conduct a coordinate-based meta-analysis to identify consistent ReHo alterations in aMCI.

Results

We identified 10 studies with 11 datasets suitable for inclusion, including 378 patients with aMCI and 435 healthy controls. This meta-analysis identified significant ReHo alterations in patients with aMCI relative to healthy controls, mainly within the default mode network (DMN) (bilateral posterior cingulate cortex [PCC], right angular gyrus, bilateral middle temporal gyri, and left parahippocampal gyrus/hippocampus), executive control network (right superior parietal lobule and dorsolateral prefrontal cortex), visual network (right lingual gyrus and left middle occipital gyrus), and sensorimotor network (right paracentral lobule/supplementary motor area, right postcentral gyrus and left posterior insula). Significant heterogeneity of ReHo alterations in the bilateral PCC, left parahippocampal gyrus/hippocampus, and right superior parietal lobule/angular gyrus was observed. Exploratory meta-regression analyses indicated that general cognitive function, gender distribution, age, and education level partially contributed to this heterogeneity.

Conclusions

This study provides provisional evidence that aMCI is associated with abnormal ReHo within the DMN, executive control network, visual network, and sensorimotor network. These local functional connectivity alterations suggest coexistence of functional deficits and compensation in these networks. These findings contribute to the modeling of brain functional connectomes and to a better understanding of the neural substrates of aMCI. Confounding factors merit much attention and warrant future investigations.

Electronic supplementary material

The online version of this article (10.1186/s40035-018-0134-8) contains supplementary material, which is available to authorized users.

Gender differences in dynamic functional connectivity based on resting-state fMRI

Many neuroscience studies have found brain differences lead to the gender differences in behavior and cognitive ability. Functional connectivity is a common and effective measure to characterize brain. Most current studies based on fMRI functional connectivity basically assumed temporal stationarity across the duration of scanning, and thought that brain functional connectivity was constant in a certain period of time. However, some studies revealed that the functional connectivity was dynamic and fluctuant over time. Dynamic functional connectivity could more accurately describe changes in neural activity. A high value of flexibility indicates frequent interactions between regions. In this article, gender differences in global brain flexibility were further investigated, and twelve brain regions with significantly flexibility differences were found. The female's flexibility is lower than male's in the amygdala, hippocampus, and parahippocampal gyrus. And in the temporal lobe, precuneus, middle cingulate gyrus, superior occipital gyrus, and inferior occipital gyrus the flexibility of male group is lower than female group. The findings may improve the understanding and provide new insights into gender differences on behaviors and cognition from the perspective of resting-state brain function.

Transcranial direct current stimulation of the medial prefrontal cortex dampens mind-wandering in men

Mind-wandering, the mind’s capacity to stray from external events and generate task-unrelated thought, has been associated with activity in the brain default network. To date, little is understood about the contribution of individual nodes of this network to mind-wandering. Here, we investigated the role of medial prefrontal cortex (mPFC) in mind-wandering, by perturbing this region with transcranial direct current stimulation (tDCS). Young healthy participants performed a choice reaction time task both before and after receiving cathodal tDCS over mPFC, and had their thoughts periodically sampled. We found that tDCS over mPFC - but not occipital or sham tDCS - decreased the propensity to mind-wander. The tDCS-induced reduction in mind-wandering occurred in men, but not in women, and was accompanied by a change in the content of task-unrelated though, which became more related to other people (as opposed to the self) following tDCS. These findings indicate that mPFC is crucial for mind-wandering, possibly by helping construction of self-relevant scenarios capable to divert attention inward, away from perceptual reality. Gender-related differences in tDCS-induced changes suggest that mPFC controls mind-wandering differently in men and women, which may depend on differences in the structural and functional organization of distributed brain networks governing mind-wandering, including mPFC.

Reproducibility of R-fMRI metrics on the impact of different strategies for multiple comparison correction and sample sizes

Concerns regarding reproducibility of resting-state functional magnetic resonance imaging (R-fMRI) findings have been raised. Little is known about how to operationally define R-fMRI reproducibility and to what extent it is affected by multiple comparison correction strategies and sample size. We comprehensively assessed two aspects of reproducibility, test-retest reliability and replicability, on widely used R-fMRI metrics in both between-subject contrasts of sex differences and within-subject comparisons of eyes-open and eyes-closed (EOEC) conditions. We noted permutation test with Threshold-Free Cluster Enhancement (TFCE), a strict multiple comparison correction strategy, reached the best balance between family-wise error rate (under 5%) and test-retest reliability/replicability (e.g., 0.68 for test-retest reliability and 0.25 for replicability of amplitude of low-frequency fluctuations (ALFF) for between-subject sex differences, 0.49 for replicability of ALFF for within-subject EOEC differences). Although R-fMRI indices attained moderate reliabilities, they replicated poorly in distinct datasets (replicability < 0.3 for between-subject sex differences, < 0.5 for within-subject EOEC differences). By randomly drawing different sample sizes from a single site, we found reliability, sensitivity and positive predictive value (PPV) rose as sample size increased. Small sample sizes (e.g., < 80 [40 per group]) not only minimized power (sensitivity < 2%), but also decreased the likelihood that significant results reflect "true" effects (PPV < 0.26) in sex differences. Our findings have implications for how to select multiple comparison correction strategies and highlight the importance of sufficiently large sample sizes in R-fMRI studies to enhance reproducibility. Hum Brain Mapp 39:300-318, 2018. © 2017 Wiley Periodicals, Inc.

Gender differences in the structural connectome of the teenage brain revealed by generalized q-sampling MRI

The question of whether there are biological differences between male and female brains is a fraught one, and political positions and prior expectations seem to have a strong influence on the interpretation of scientific data in this field. This question is relevant to issues of gender differences in the prevalence of psychiatric conditions, including autism, attention deficit hyperactivity disorder (ADHD), Tourette's syndrome, schizophrenia, dyslexia, depression, and eating disorders. Understanding how gender influences vulnerability to these conditions is significant. Diffusion magnetic resonance imaging (dMRI) provides a non-invasive method to investigate brain microstructure and the integrity of anatomical connectivity. Generalized q-sampling imaging (GQI) has been proposed to characterize complicated fiber patterns and distinguish fiber orientations, providing an opportunity for more accurate, higher-order descriptions through the water diffusion process. Therefore, we aimed to investigate differences in the brain's structural network between teenage males and females using GQI. This study included 59 (i.e., 33 males and 26 females) age- and education-matched subjects (age range: 13 to 14 years). The structural connectome was obtained by graph theoretical and network-based statistical (NBS) analyses. Our findings show that teenage male brains exhibit better intrahemispheric communication, and teenage female brains exhibit better interhemispheric communication. Our results also suggest that the network organization of teenage male brains is more local, more segregated, and more similar to small-world networks than teenage female brains. We conclude that the use of an MRI study with a GQI-based structural connectomic approach like ours presents novel insights into network-based systems of the brain and provides a new piece of the puzzle regarding gender differences.

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The GQI-based structural connectomic study provides a new piece of the puzzle regarding gender differences.

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Male brains exhibit better intrahemispheric communication, and female exhibit better interhemispheric communication.

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The network organization of teenage male brains is more local and more segregated than teenage female brains.

The Effects of Age, from Young to Middle Adulthood, and Gender on Resting State Functional Connectivity of the Dopaminergic Midbrain

Dysfunction of the dopaminergic ventral tegmental area (VTA) and substantia nigra pars compacta (SNc) is implicated in psychiatric disorders including attention-deficit/ hyperactivity disorder (ADHD), addiction, schizophrenia and movement disorders such as Parkinson's disease (PD). Although the prevalence of these disorders varies by age and sex, the underlying neural mechanism is not well understood. The objective of this study was to delineate the distinct resting state functional connectivity (rsFC) of the VTA and SNc and examine the effects of age, from young to middle-adulthood, and sex on the rsFC of these two dopaminergic structures in a data set of 250 healthy adults (18-49 years of age, 104 men). Using blood oxygenation level dependent (BOLD) signals, we correlated the time course of the VTA and SNc to the time courses of all other brain voxels. At a corrected threshold, paired t-test showed stronger VTA connectivity to bilateral angular gyrus and superior/middle and orbital frontal regions and stronger SNc connectivity to the insula, thalamus, parahippocampal gyrus (PHG) and amygdala. Compared to women, men showed a stronger VTA/SNc connectivity to the left posterior orbital gyrus. In linear regressions, men but not women showed age-related changes in VTA/SNc connectivity to a number of cortical and cerebellar regions. Supporting shared but also distinct cerebral rsFC of the VTA and SNc and gender differences in age-related changes from young and middle adulthood in VTA/SNc connectivity, these new findings help advance our understanding of the neural bases of many neuropsychiatric illnesses that implicate the dopaminergic systems.

Adolescent Major Depressive Disorder: Neuroimaging Evidence of Sex Difference during an Affective Go/No-Go Task

Compared to female major depressive disorder (MDD), male MDD often receives less attention. However, research is warranted since there are significant sex differences in the clinical presentation of MDD and a higher rate of suicide in depressed men. To the best of our knowledge, this is the first functional magnetic resonance imaging (fMRI) study with a large sample addressing putative sex differences in MDD during adolescence, a period when one of the most robust findings in psychiatric epidemiology emerges; that females are twice as likely to suffer from MDD than males. Twenty-four depressed and 10 healthy male adolescents, together with 82 depressed and 24 healthy female adolescents, aged 11-18 years, undertook an affective go/no-go task during fMRI acquisition. In response to sad relative to neutral distractors, significant sex differences (in the supramarginal gyrus) and group-by-sex interactions (in the supramarginal gyrus and the posterior cingulate cortex) were found. Furthermore, in contrast to the healthy male adolescents, depressed male adolescents showed decreased activation in the cerebellum with a significant group-by-age interaction in connectivity. Future research may consider altered developmental trajectories and the possible implications of sex-specific treatment and prevention strategies for MDD.

Altered Resting-State Signals in Patients with Acute Stroke In or Under the Thalamus

Previous studies have suggested that cortical functional reorganization is associated with motor recovery after stroke and that normal afferent sensory information is very important in that process. In this study, we selected patients who had a stroke in or under the thalamus, with potentially impaired afferent sensory information and analyzed the differences between these patients and healthy controls at three levels: brain regions, the functional connectivity between brain areas, and the whole-brain functional network. Compared with healthy controls, regional homogeneities in the left middle temporal gyrus decreased and functional connectivity between the left middle temporal gyrus and the stroke area increased in the patients. However, there was no significant change in the whole-brain functional network. By focusing on stroke located in or under the thalamus, our study contributes to wider inquiries into understanding and treating stroke.

Intrinsic connectivity networks from childhood to late adolescence: Effects of age and sex

There is limited evidence on the effects of age and sex on intrinsic connectivity of networks underlying cognition during childhood and adolescence. Independent component analysis was conducted in 113 subjects aged 7-18; the default mode, executive control, anterior salience, basal ganglia, language and visuospatial networks were identified. The effect of age was examined with multiple regression, while sex and 'age × sex' interactions were assessed by dividing the sample according to age (7-12 and 13-18 years). As age increased, connectivity in the dorsal and ventral default mode network became more anterior and posterior, respectively, while in the executive control network, connectivity increased within frontoparietal regions. The basal ganglia network showed increased engagement of striatum, thalami and precuneus. The anterior salience network showed greater connectivity in frontal areas and anterior cingulate, and less connectivity of orbitofrontal, middle cingulate and temporoparietal regions. The language network presented increased connectivity of inferior frontal and decreased connectivity within the right middle frontal and left inferior parietal cortices. The visuospatial network showed greater engagement of inferior parietal and frontal cortices. No effect of sex, nor age by sex interactions was observed. These findings provide evidence of strengthening of cortico-cortical and cortico-subcortical networks across childhood and adolescence.

Functional connectivity alterations in the motor and fronto-parietal network relate to behavioral heterogeneity in Parkinson's disease

BACKGROUND

Insight into the neural mechanisms of postural instability and gait disorder (PIGD) and tremor dominant (TD) subtypes in Parkinson's disease (PD) is indispensable for generating pathophysiology hypotheses underlying this phenotyping. This cross-sectional study aimed to gain insight in specific and brain-wide functional connectivity (FC) and its correlation with motor deterioration and preservation in PD subtypes.

METHODS

68 PD patients classified as PIGD (n = 41), TD (n = 19) or indeterminate (n = 8) and 19 age-matched controls underwent resting-state fMRI while 'off' medication to assess FC between regions of interest (ROIs) in the motor and fronto-parietal network and on a whole-brain level using a parcellated template. FC alterations were correlated with quantitative behavioral measures.

RESULTS

ROI-analyses showed decreased FC between the caudate and putamen in PIGD compared to TD. This hypo-connectivity was correlated with behavioral impairment. In contrast, TD-specific hyper-connectivity between motor cortical areas and the inferior parietal lobule correlated with less behavioral impairment, suggesting compensatory mechanisms. Both subgroups showed hyper-connectivity between the left supplementary motor area and pedunculopontine nucleus, whereas PIGD-specific right lateralized hyper-connectivity was shown between this nucleus and the premotor cortex. Whole-brain analyses revealed 65% hypo-connectivity and 35% hyper-connectivity in PIGD compared to TD. TD also revealed primarily hypo-connectivity compared to controls, but had more pronounced hyper-connectivity involving temporo-occipital areas.

CONCLUSION

This multilevel analysis showed differential connectivity alterations in large scale neural networks and between motor and cognitive control areas that related to behavioral heterogeneity in PD, underscoring the classic TD-PIGD phenotypical classification.