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1.
Genet Med ; 23(5): 872-880, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33564151

RESUMO

PURPOSE: To understand the consequences of the 3q29 deletion on medical, neurodevelopmental, psychiatric, brain structural, and neurological sequalae by systematic evaluation of affected individuals. To develop evidence-based recommendations using these data for effective clinical care. METHODS: Thirty-two individuals with the 3q29 deletion were evaluated using a defined phenotyping protocol and standardized data collection instruments. RESULTS: Medical manifestations were varied and reported across nearly every organ system. The most severe manifestations were congenital heart defects (25%) and the most common were gastrointestinal symptoms (81%). Physical examination revealed a high proportion of musculoskeletal findings (81%). Neurodevelopmental phenotypes represent a significant burden and include intellectual disability (34%), autism spectrum disorder (38%), executive function deficits (46%), and graphomotor weakness (78%). Psychiatric illness manifests across the lifespan with psychosis prodrome (15%), psychosis (20%), anxiety disorders (40%), and attention deficit-hyperactivity disorder (ADHD) (63%). Neuroimaging revealed structural anomalies of the posterior fossa, but on neurological exam study subjects displayed only mild or moderate motor vulnerabilities. CONCLUSION: By direct evaluation of 3q29 deletion study subjects, we document common features of the syndrome, including a high burden of neurodevelopmental and neuropsychiatric phenotypes. Evidence-based recommendations for evaluation, referral, and management are provided to help guide clinicians in the care of 3q29 deletion patients.

2.
IEEE Trans Med Imaging ; 40(5): 1363-1376, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33507867

RESUMO

To better understand early brain development in health and disorder, it is critical to accurately segment infant brain magnetic resonance (MR) images into white matter (WM), gray matter (GM), and cerebrospinal fluid (CSF). Deep learning-based methods have achieved state-of-the-art performance; h owever, one of the major limitations is that the learning-based methods may suffer from the multi-site issue, that is, the models trained on a dataset from one site may not be applicable to the datasets acquired from other sites with different imaging protocols/scanners. To promote methodological development in the community, the iSeg-2019 challenge (http://iseg2019.web.unc.edu) provides a set of 6-month infant subjects from multiple sites with different protocols/scanners for the participating methods. T raining/validation subjects are from UNC (MAP) and testing subjects are from UNC/UMN (BCP), Stanford University, and Emory University. By the time of writing, there are 30 automatic segmentation methods participated in the iSeg-2019. In this article, 8 top-ranked methods were reviewed by detailing their pipelines/implementations, presenting experimental results, and evaluating performance across different sites in terms of whole brain, regions of interest, and gyral landmark curves. We further pointed out their limitations and possible directions for addressing the multi-site issue. We find that multi-site consistency is still an open issue. We hope that the multi-site dataset in the iSeg-2019 and this review article will attract more researchers to address the challenging and critical multi-site issue in practice.

3.
Magn Reson Imaging ; 77: 194-203, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-33359631

RESUMO

BACKGROUND: Diffusion MRI (dMRI) data acquisition protocols are well-established on modern high-field clinical scanners for human studies. However, these protocols are not suitable for the chimpanzee (or other large-brained mammals) because of its substantial difference in head geometry and brain volume compared with humans. Therefore, an optimal dMRI data acquisition protocol dedicated to chimpanzee neuroimaging is needed. METHODS: A multi-shot (4 segments) double spin-echo echo-planar imaging (MS-EPI) sequence and a single-shot double spin-echo EPI (SS-EPI) sequence were optimized separately for in vivo dMRI data acquisition of chimpanzees using a clinical 3T scanner. Correction for severe susceptibility-induced image distortion and signal drop-off of the chimpanzee brain was performed and evaluated using FSL software. DTI indices in different brain regions and probabilistic tractography were compared. A separate DTI data set from n=34 chimpanzees (13 to 56 years old) was collected using the optimal protocol. Age-related changes in diffusivity indices of optic nerve fibers were evaluated. RESULTS: The SS-EPI sequence acquired dMRI data of the chimpanzee brain with approximately doubled the SNR as the MS-EPI sequence given the same scan time. The quality of white matter fiber tracking from the SS-EPI data was much higher than that from MS-EPI data. However, quantitative analysis of DTI indices showed no difference in most ROIs between the SS-EPI and MS-EPI sequences. The progressive evolution of diffusivity indices of optic nerves indicated mild changes in fiber bundles of chimpanzees aged 40 years and above. CONCLUSION: The single-shot EPI-based acquisition protocol provided better image quality of dMRI for chimpanzee brains and is recommended for in vivo dMRI study or clinical diagnosis of chimpanzees (or other large animals) using a clinical scanner. Also, the tendency of FA decrease or diffusivity increase in the optic nerve of aged chimpanzees was seen but did not show significant age-related changes, suggesting aging may have less impact on optic nerve fiber integrity of chimpanzees, in contrast to previous results for both macaque monkeys and humans.


Assuntos
Envelhecimento/fisiologia , Encéfalo/diagnóstico por imagem , Encéfalo/fisiologia , Imagem de Difusão por Ressonância Magnética/métodos , Nervo Óptico/diagnóstico por imagem , Animais , Imagem Ecoplanar/métodos , Feminino , Masculino , Neuroimagem , Pan troglodytes
4.
PLoS Biol ; 18(12): e3000971, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-33383575

RESUMO

Chimpanzees (Pan troglodytes) are, along with bonobos, humans' closest living relatives. The advent of diffusion MRI tractography in recent years has allowed a resurgence of comparative neuroanatomical studies in humans and other primate species. Here we offer, in comparative perspective, the first chimpanzee white matter atlas, constructed from in vivo chimpanzee diffusion-weighted scans. Comparative white matter atlases provide a useful tool for identifying neuroanatomical differences and similarities between humans and other primate species. Until now, comprehensive fascicular atlases have been created for humans (Homo sapiens), rhesus macaques (Macaca mulatta), and several other nonhuman primate species, but never in a nonhuman ape. Information on chimpanzee neuroanatomy is essential for understanding the anatomical specializations of white matter organization that are unique to the human lineage.


Assuntos
Pan troglodytes/anatomia & histologia , Substância Branca/anatomia & histologia , Anatomia Artística/métodos , Animais , Atlas como Assunto , Encéfalo/anatomia & histologia , Mapeamento Encefálico/métodos , Imagem de Difusão por Ressonância Magnética/métodos , Imagem de Tensor de Difusão/métodos , Feminino , Processamento de Imagem Assistida por Computador/métodos , Imagem por Ressonância Magnética/métodos , Masculino
5.
Elife ; 92020 Mar 23.
Artigo em Inglês | MEDLINE | ID: mdl-32202497

RESUMO

Evolutionary adaptations of temporo-parietal cortex are considered to be a critical specialization of the human brain. Cortical adaptations, however, can affect different aspects of brain architecture, including local expansion of the cortical sheet or changes in connectivity between cortical areas. We distinguish different types of changes in brain architecture using a computational neuroanatomy approach. We investigate the extent to which between-species alignment, based on cortical myelin, can predict changes in connectivity patterns across macaque, chimpanzee, and human. We show that expansion and relocation of brain areas can predict terminations of several white matter tracts in temporo-parietal cortex, including the middle and superior longitudinal fasciculus, but not the arcuate fasciculus. This demonstrates that the arcuate fasciculus underwent additional evolutionary modifications affecting the temporal lobe connectivity pattern. This approach can flexibly be extended to include other features of cortical organization and other species, allowing direct tests of comparative hypotheses of brain organization.

6.
Brain ; 142(12): 3991-4002, 2019 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-31724729

RESUMO

The genetic basis and human-specific character of schizophrenia has led to the hypothesis that human brain evolution may have played a role in the development of the disorder. We examined schizophrenia-related changes in brain connectivity in the context of evolutionary changes in human brain wiring by comparing in vivo neuroimaging data from humans and chimpanzees, one of our closest living evolutionary relatives and a species with which we share a very recent common ancestor. We contrasted the connectome layout between the chimpanzee and human brain and compared differences with the pattern of schizophrenia-related changes in brain connectivity as observed in patients. We show evidence of evolutionary modifications of human brain connectivity to significantly overlap with the cortical pattern of schizophrenia-related dysconnectivity (P < 0.001, permutation testing). We validated these effects in three additional, independent schizophrenia datasets. We further assessed the specificity of effects by examining brain dysconnectivity patterns in seven other psychiatric and neurological brain disorders (including, among others, major depressive disorder and obsessive-compulsive disorder, arguably characterized by behavioural symptoms that are less specific to humans), which showed no such associations with modifications of human brain connectivity. Comparisons of brain connectivity across humans, chimpanzee and macaques further suggest that features of connectivity that evolved in the human lineage showed the strongest association to the disorder, that is, brain circuits potentially related to human evolutionary specializations. Taken together, our findings suggest that human-specific features of connectome organization may be enriched for changes in brain connectivity related to schizophrenia. Modifications in human brain connectivity in service of higher order brain functions may have potentially also rendered the brain vulnerable to brain dysfunction.


Assuntos
Evolução Biológica , Encéfalo/fisiopatologia , Rede Nervosa/fisiopatologia , Esquizofrenia/fisiopatologia , Adulto , Animais , Encéfalo/diagnóstico por imagem , Conectoma , Feminino , Humanos , Imagem por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Rede Nervosa/diagnóstico por imagem , Pan troglodytes , Esquizofrenia/diagnóstico por imagem
7.
Nat Commun ; 10(1): 4839, 2019 10 24.
Artigo em Inglês | MEDLINE | ID: mdl-31649260

RESUMO

Cognitive brain networks such as the default-mode network (DMN), frontoparietal network, and salience network, are key functional networks of the human brain. Here we show that the rapid evolutionary cortical expansion of cognitive networks in the human brain, and most pronounced the DMN, runs parallel with high expression of human-accelerated genes (HAR genes). Using comparative transcriptomics analysis, we present that HAR genes are differentially more expressed in higher-order cognitive networks in humans compared to chimpanzees and macaques and that genes with high expression in the DMN are involved in synapse and dendrite formation. Moreover, HAR and DMN genes show significant associations with individual variations in DMN functional activity, intelligence, sociability, and mental conditions such as schizophrenia and autism. Our results suggest that the expansion of higher-order functional networks subserving increasing cognitive properties has been an important locus of genetic changes in recent human brain evolution.


Assuntos
Encéfalo/metabolismo , Cognição , Evolução Molecular , Vias Neurais/metabolismo , Animais , Encéfalo/diagnóstico por imagem , Mapeamento Encefálico , Dendritos , Perfilação da Expressão Gênica , Humanos , Macaca/genética , Imagem por Ressonância Magnética , Vias Neurais/diagnóstico por imagem , Pan troglodytes/genética , Sinapses
8.
Proc Natl Acad Sci U S A ; 116(14): 7101-7106, 2019 04 02.
Artigo em Inglês | MEDLINE | ID: mdl-30886094

RESUMO

The development of complex cognitive functions during human evolution coincides with pronounced encephalization and expansion of white matter, the brain's infrastructure for region-to-region communication. We investigated adaptations of the human macroscale brain network by comparing human brain wiring with that of the chimpanzee, one of our closest living primate relatives. White matter connectivity networks were reconstructed using diffusion-weighted MRI in humans (n = 57) and chimpanzees (n = 20) and then analyzed using network neuroscience tools. We demonstrate higher network centrality of connections linking multimodal association areas in humans compared with chimpanzees, together with a more pronounced modular topology of the human connectome. Furthermore, connections observed in humans but not in chimpanzees particularly link multimodal areas of the temporal, lateral parietal, and inferior frontal cortices, including tracts important for language processing. Network analysis demonstrates a particularly high contribution of these connections to global network integration in the human brain. Taken together, our comparative connectome findings suggest an evolutionary shift in the human brain toward investment of neural resources in multimodal connectivity facilitating neural integration, combined with an increase in language-related connectivity supporting functional specialization.


Assuntos
Encéfalo/crescimento & desenvolvimento , Encéfalo/fisiologia , Imagem Multimodal/métodos , Adulto , Idoso , Animais , Encéfalo/diagnóstico por imagem , Mapeamento Encefálico , Cognição , Conectoma/métodos , Imagem de Difusão por Ressonância Magnética/métodos , Feminino , Humanos , Processamento de Imagem Assistida por Computador , Idioma , Pessoa de Meia-Idade , Rede Nervosa/diagnóstico por imagem , Rede Nervosa/crescimento & desenvolvimento , Rede Nervosa/fisiologia , Pan troglodytes , Substância Branca/diagnóstico por imagem , Substância Branca/crescimento & desenvolvimento , Adulto Jovem
9.
Cortex ; 118: 223-243, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-30910223

RESUMO

There is evidence for enlargement of association cortex in humans compared to other primate species. Expansion of temporal association cortex appears to have displaced extrastriate cortex posteriorly and inferiorly in humans compared to macaques. However, the details of the organization of these recently expanded areas are still being uncovered. Here, we used diffusion tractography to examine the organization of extrastriate and temporal association cortex in chimpanzees, humans, and macaques. Our goal was to characterize the organization of visual and auditory association areas with respect to their corresponding primary areas (primary visual cortex and auditory core) in humans and chimpanzees. We report three results: (1) Humans, chimpanzees, and macaques show expected retinotopic organization of primary visual cortex (V1) connectivity to V2 and to areas immediately anterior to V2; (2) In contrast to macaques, chimpanzee and human V1 shows apparent connectivity with lateral, inferior, and anterior temporal regions, beyond the retinotopically organized extrastriate areas; (3) Also in contrast to macaques, chimpanzee and human auditory core shows apparent connectivity with temporal association areas, with some important differences between humans and chimpanzees. Diffusion tractography reconstructs diffusion patterns that reflect white matter organization, but does not definitively represent direct anatomical connectivity. Therefore, it is important to recognize that our findings are suggestive of species differences in long-distance white matter organization rather than demonstrations of direct connections. Our data support the conclusion that expansion of temporal association cortex, and the resulting posterior displacement of extrastriate cortex, occurred in the human lineage after its separation from the chimpanzee lineage. It is possible, however, that some expansion of the temporal lobe occurred prior to the separation of humans and chimpanzees, reflected in the reorganization of long white matter tracts in the temporal lobe that connect occipital areas to the fusiform gyrus, middle temporal gyrus, and anterior temporal lobe.


Assuntos
Mapeamento Encefálico , Lobo Temporal/anatomia & histologia , Campos Visuais/fisiologia , Vias Visuais/anatomia & histologia , Animais , Mapeamento Encefálico/métodos , Humanos , Processamento de Imagem Assistida por Computador/métodos , Macaca mulatta , Pan troglodytes/anatomia & histologia , Córtex Visual
10.
Brain Struct Funct ; 224(3): 1021-1033, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30569281

RESUMO

Understanding the phylogeny of the human brain requires an appreciation of brain organization of our closest animal relatives. Neuroimaging tools such as magnetic resonance imaging (MRI) allow us to study whole-brain organization in species which can otherwise not be studied. Here, we used diffusion MRI to reconstruct the connections of the cortical hemispheres of the chimpanzee. This allowed us to perform an exploratory analysis of the grey matter structures of the chimpanzee cerebral cortex and their underlying white matter connectivity profiles. We identified a number of networks that strongly resemble those found in other primates, including the corticospinal system, limbic connections through the cingulum bundle and fornix, and occipital-temporal and temporal-frontal systems. Notably, chimpanzee temporal cortex showed a strong resemblance to that of the human brain, providing some insight into the specialization of the two species' shared lineage.


Assuntos
Mapeamento Encefálico , Substância Cinzenta/diagnóstico por imagem , Vias Neurais/diagnóstico por imagem , Pan troglodytes/anatomia & histologia , Substância Branca/diagnóstico por imagem , Animais , Feminino , Imageamento Tridimensional , Imagem por Ressonância Magnética , Fibras Nervosas
11.
Brain Connect ; 8(9): 537-548, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30280929

RESUMO

Although a large body of research has identified discrete neuroanatomical regions involved in social cognition and behavior (the "social brain"), the existing findings are based largely on studies of specific brain structures defined within the context of particular tasks or for specific types of social behavior. The objective of the current work was to view these regions as nodes of a larger collective network and to quantitatively characterize both the topology of that network and the relative criticality of its many nodes. Large-scale data mining was performed to generate seed regions of the social brain. High-quality diffusion MRI data of typical adults were used to map anatomical networks of the social brain. Network topology and nodal centrality were analyzed using graph theory. The structural social brain network demonstrates a high degree of global functional integration with strong local segregation. Bilateral dorsomedial prefrontal cortices and amygdala play the most central roles in the network. Strong probabilistic evidence supports modular divisions of the social brain into subnetworks bearing good resemblance to functionally classified clusters. The present network-driven approach quantifies the structural topology of the social brain as a whole. This work can serve as a critical benchmark against which to compare (1) developmental change in social brain topology over time (from infancy through adolescence and beyond) and (2) atypical network topologies that may be a sign or symptom of disorder (as in conditions such as autism, Williams syndrome, schizophrenia, and others).


Assuntos
Mapeamento Encefálico/métodos , Encéfalo/fisiologia , Psicologia Social/métodos , Adulto , Tonsila do Cerebelo/fisiologia , Big Data , Conectoma , Feminino , Humanos , Processamento de Imagem Assistida por Computador , Relações Interpessoais , Imagem por Ressonância Magnética/métodos , Masculino , Rede Nervosa/fisiologia , Vias Neurais/fisiologia , Córtex Pré-Frontal/fisiologia
12.
Comput Med Imaging Graph ; 69: 9-20, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30170273

RESUMO

Accurate assessment of connectional anatomy of primate brains can be an important avenue to better understand the structural and functional organization of brains. To this end, numerous connectome projects have been initiated to create a comprehensive map of the connectional anatomy over a large spatial expanse. Tractography based on diffusion MRI (dMRI) data has been used as a tool by many connectome projects in that it is widely used to visualize axonal pathways and reveal microstructural features on living brains. However, the measures obtained from dMRI are indirect inference of microstructures. This intrinsic limitation reduces the reliability of dMRI in constructing connectomes for brains. In this work, we proposed a framework to increase the accuracy of constructing a dMRI-based connectome on macaque brains by integrating meso-scale connective information from tract-tracing data and micro-scale axonal orientation information from myelin stain data. Our results suggest that this integrative framework could advance the mapping accuracy of dMRI based connections and axonal pathways, and demonstrate the prospect of the proposed framework in constructing a large-scale connectome on living primate brains.


Assuntos
Encéfalo/anatomia & histologia , Conectoma/métodos , Imagem de Difusão por Ressonância Magnética , Macaca , Neurônios , Algoritmos , Animais , Corantes , Bases de Dados Factuais , Bainha de Mielina
13.
Neuroimage Clin ; 20: 485-497, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30148064

RESUMO

Adult survivors of pediatric brain tumors exhibit deficits in executive functioning. Given that brain tumors and medical treatments for brain tumors result in disruptions to white matter, a network analysis was used to explore the topological properties of white matter networks. This study used diffusion tensor imaging and deterministic tractography in 38 adult survivors of pediatric brain tumors (mean age in years = 23.11 (SD = 4.96), 54% female, mean years post diagnosis = 14.09 (SD = 6.19)) and 38 healthy peers matched by age, gender, handedness, and socioeconomic status. Nodes were defined using the Automated Anatomical Labeling (AAL) parcellation scheme, and edges were defined as the mean fractional anisotropy of streamlines that connected each node pair. Global efficiency and average clustering coefficient were reduced in survivors compared to healthy peers with preferential impact to hub regions. Global efficiency mediated differences in cognitive flexibility between survivors and healthy peers, as well as the relationship between cumulative neurological risk and cognitive flexibility. These results suggest that adult survivors of pediatric brain tumors, on average one and a half decades post brain tumor diagnosis and treatment, exhibit altered white matter topology in the form of suboptimal integration and segregation of large scale networks, and that disrupted topology may underlie executive functioning impairments. Network based studies provided important topographic insights on network organization in long-term survivors of pediatric brain tumor.


Assuntos
Mapeamento Encefálico/métodos , Neoplasias Encefálicas/diagnóstico por imagem , Encéfalo/diagnóstico por imagem , Cognição/fisiologia , Rede Nervosa/diagnóstico por imagem , Substância Branca/diagnóstico por imagem , Adolescente , Adulto , Encéfalo/metabolismo , Neoplasias Encefálicas/metabolismo , Criança , Imagem de Tensor de Difusão/métodos , Função Executiva/fisiologia , Humanos , Rede Nervosa/metabolismo , Vias Neurais/diagnóstico por imagem , Vias Neurais/metabolismo , Sobreviventes , Substância Branca/metabolismo , Adulto Jovem
14.
BMC Psychiatry ; 18(1): 183, 2018 06 08.
Artigo em Inglês | MEDLINE | ID: mdl-29884173

RESUMO

BACKGROUND: 3q29 deletion syndrome is caused by a recurrent hemizygous 1.6 Mb deletion on the long arm of chromosome 3. The syndrome is rare (1 in 30,000 individuals) and is associated with mild to moderate intellectual disability, increased risk for autism and anxiety, and a 40-fold increased risk for schizophrenia, along with a host of physical manifestations. However, the disorder is poorly characterized, the range of manifestations is not well described, and the underlying molecular mechanism is not understood. We designed the Emory 3q29 Project to document the range of neurodevelopmental and psychiatric manifestations associated with 3q29 deletion syndrome. We will also create a biobank of samples from our 3q29 deletion carriers for mechanistic studies, which will be a publicly-available resource for qualified investigators. The ultimate goals of our study are three-fold: first, to improve management and treatment of 3q29 deletion syndrome. Second, to uncover the molecular mechanism of the disorder. Third, to enable cross-disorder comparison with other rare genetic syndromes associated with neuropsychiatric phenotypes. METHODS: We will ascertain study subjects, age 6 and older, from our existing registry ( 3q29deletion.org ). Participants and their families will travel to Atlanta, GA for phenotypic assessments, with particular emphasis on evaluation of anxiety, cognitive ability, autism symptomatology, and risk for psychosis via prodromal symptoms and syndromes. Evaluations will be performed using standardized instruments. Structural, diffusion, and resting-state functional MRI data will be collected from eligible study participants. We will also collect blood from the 3q29 deletion carrier and participating family members, to be banked at the NIMH Repository and Genomics Resource (NRGR). DISCUSSION: The study of 3q29 deletion has the potential to transform our understanding of complex disease. Study of individuals with the deletion may provide insights into long term care and management of the disorder. Our project describes the protocol for a prospective study of the behavioral and clinical phenotype associated with 3q29 deletion syndrome. The paradigm described here could easily be adapted to study additional CNV or single gene disorders with high risk for neuropsychiatric phenotypes, and/or transferred to other study sites, providing a means for data harmonization and cross-disorder analysis.


Assuntos
Transtorno Autístico , Deleção Cromossômica , Transtornos Cromossômicos , Cromossomos Humanos Par 3 , Deficiência Intelectual , Esquizofrenia , Transtorno Autístico/diagnóstico , Transtorno Autístico/genética , Transtorno Autístico/psicologia , Criança , Transtornos Cromossômicos/diagnóstico , Transtornos Cromossômicos/genética , Transtornos Cromossômicos/psicologia , Cognição , Deficiências do Desenvolvimento/diagnóstico , Deficiências do Desenvolvimento/etiologia , Deficiências do Desenvolvimento/psicologia , Feminino , Humanos , Deficiência Intelectual/diagnóstico , Deficiência Intelectual/genética , Deficiência Intelectual/psicologia , Masculino , Fenótipo , Estudos Prospectivos , Esquizofrenia/diagnóstico , Esquizofrenia/genética , Esquizofrenia/terapia , Psicologia do Esquizofrênico
15.
J Comput Neurosci ; 42(3): 217-229, 2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28271301

RESUMO

Mammalian cerebral cortices are characterized by elaborate convolutions. Radial convolutions exhibit homology across primate species and generally are easily identified in individuals of the same species. In contrast, circumferential convolutions vary across species as well as individuals of the same species. However, systematic study of circumferential convolution patterns is lacking. To address this issue, we utilized structural MRI (sMRI) and diffusion MRI (dMRI) data from primate brains. We quantified cortical thickness and circumferential convolutions on gyral banks in relation to axonal pathways and density along the gray matter/white matter boundaries. Based on these observations, we performed a series of computational simulations. Results demonstrated that the interplay of heterogeneous cortex growth and mechanical forces along axons plays a vital role in the regulation of circumferential convolutions. In contrast, gyral geometry controls the complexity of circumferential convolutions. These findings offer insight into the mystery of circumferential convolutions in primate brains.


Assuntos
Córtex Cerebral , Modelos Neurológicos , Primatas , Animais , Encéfalo , Mapeamento Encefálico , Humanos
16.
Brain Struct Funct ; 222(5): 2127-2141, 2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-27796591

RESUMO

Cortical folding pattern analysis is very important to understand brain organization and development. Since previous studies mostly focus on human brain cortex, the regularity and variability of cortical folding patterns across primate brains (macaques, chimpanzees and human) remain largely unknown. This paper presents a novel computational framework to identify common or unique gyral folding patterns in macaque, chimpanzee and human brains using magnetic resonance imaging (MRI) data. We quantitatively characterize gyral folding patterns via hinge numbers with cortical surfaces constructed from MRI data, and identify 6 common three-hinge gyral folds that exhibit consistent anatomical locations across these three species as well as 2 unique three hinges in macaque, 6 ones in chimpanzee and 14 ones in human. A novel morphology descriptor is then applied to classify three-hinge gyral folds, and the increasing complexity is identified among the species analyzed. This study may provide novel insights into the regularity and variability of the cerebral cortex from developmental perspective and may potentially facilitate novel neuroimage analyses such as cortical parcellation with correspondences across species in the future.


Assuntos
Encéfalo/anatomia & histologia , Especificidade da Espécie , Algoritmos , Animais , Humanos , Aumento da Imagem/métodos , Imageamento Tridimensional/métodos , Macaca , Imagem por Ressonância Magnética/métodos , Pan troglodytes
17.
CNS Neurosci Ther ; 23(2): 155-161, 2017 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-27860375

RESUMO

AIMS: The thalamus is a major relay station that modulates input from many cortical areas and a filter for sensory input and is involved in the pathophysiology of amyotrophic lateral sclerosis (ALS). However, it still remains unclear whether all thalamocortical networks are affected or whether there is selective vulnerability. In this study, we aimed to study the selective vulnerability of different thalamocortical structural connections in ALS and to test the hypothesis of a specific impairment in motor-related thalamocortical connectivity. METHODS: Diffusion tensor imaging (DTI) tractography was used to identify thalamocortical structural pathways in 38 individuals with ALS and 35 gender/age-matched control subjects. Thalami of both groups were parcellated into subregions based on local patterns of thalamocortical connectivity. DTI measures of these distinct thalamocortical connections were derived and compared between groups. RESULTS: The analysis of probabilistic tractography showed that the structural connectivity between bilateral pre/primary motor cortices and associated thalamic subregions was specifically impaired in patients with ALS, while the other thalamocortical connections remained relatively intact. In addition, fractional anisotropy values of the impaired thalamocortical motor pathway were inversely correlated with the disease duration. CONCLUSION: Our findings provide direct evidence for selective impairment of the thalamocortical structural connectivity in ALS.


Assuntos
Esclerose Amiotrófica Lateral/patologia , Córtex Cerebral/patologia , Vias Neurais/fisiologia , Tálamo/patologia , Adulto , Esclerose Amiotrófica Lateral/diagnóstico por imagem , Anisotropia , Córtex Cerebral/diagnóstico por imagem , Imagem de Tensor de Difusão , Feminino , Lateralidade Funcional , Humanos , Processamento de Imagem Assistida por Computador , Masculino , Pessoa de Meia-Idade , Vias Neurais/diagnóstico por imagem , Tálamo/diagnóstico por imagem
18.
J Neurol Neurosurg Psychiatry ; 88(5): 369-370, 2017 05.
Artigo em Inglês | MEDLINE | ID: mdl-27913627

RESUMO

OBJECTIVE: Amyotrophic lateral sclerosis (ALS) is an idiopathic and fatal neurodegenerative disease of the human motor system. While microstructural alterations in corpus callosum (CC) have been identified as a consistent feature of ALS, studies directly examining interhemispheric neural connectivity are still lacking. To shed more light on the pathophysiology of ALS, the present study aims to examine alterations of interhemispheric structural and functional connectivity in individuals with ALS. METHODS: Diffusion tensor imaging (DTI) and resting-state functional MRI (rfMRI) data were acquired from 38 individuals with ALS and 35 gender-matched and age-matched control subjects. Indices of interhemispheric functional and structural neural connection were derived with analyses of voxel mirrored homotopic connectivity (VMHC) and probabilistic fibre tracking. RESULTS: The rfMRI has revealed extensive reductions of VMHC associated with ALS in brain regions of the precentral and postcentral gyrus, the paracentral lobule, the superior temporal gyrus, the middle cingulate gyrus, the putamen and the superior parietal lobules. With DTI, the analysis has also revealed reductions of interhemispheric structural connectivity through the CC subregions II, III and V in patients with ALS. Additionally, interhemispheric functional connectivity of the bilateral precentral gyri positively correlated with fractional anisotropy values of the CC subregion III, which structurally connects the bilateral motor cortices. CONCLUSIONS: The present data provided direct evidence confirming and extending the view of impaired interhemispheric neural communications mediated by CC, providing a new perspective for examinations and understanding the pathophysiology of ALS.


Assuntos
Esclerose Amiotrófica Lateral/fisiopatologia , Corpo Caloso/fisiopatologia , Vias Neurais/fisiopatologia , Esclerose Amiotrófica Lateral/diagnóstico por imagem , Córtex Cerebral/patologia , Corpo Caloso/anatomia & histologia , Imagem de Tensor de Difusão/métodos , Humanos , Processamento de Imagem Assistida por Computador , Imagem por Ressonância Magnética/métodos
19.
Hum Brain Mapp ; 37(3): 954-67, 2016 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26706823

RESUMO

The thalamus is a relay center between various subcortical brain areas and the cerebral cortex with delineation of its constituent nuclei being of particular interest in many applications. While previous studies have demonstrated efficacy of connectivity-based thalamus segmentation, they used approaches that do not consider the dynamic nature of thalamo-cortical interactions. In this study, we explicitly exploited the dynamic variation of thalamo-cortical connections to identify different states of functional connectivity and performed state-specific thalamus parcellation. With normalized spectral clustering successively applied in temporal and spatial domains, nine thalamo-cortical connectivity states were identified and the dynamic thalamus parcellation revealed finer thalamic structures with improved atlas correspondence. The present results extend our understanding of thalamo-cortical connectivity and provide a more comprehensive view of the thalamo-cortical interaction.


Assuntos
Imagem por Ressonância Magnética/métodos , Tálamo/fisiologia , Córtex Cerebral/fisiologia , Conectoma , Conjuntos de Dados como Assunto , Humanos , Internet , Vias Neurais/fisiologia , Descanso
20.
Artigo em Inglês | MEDLINE | ID: mdl-26501133

RESUMO

Assessment of structural connectivity patterns of brains can be an important avenue for better understanding mechanisms of structural and functional brain architectures. Therefore, many efforts have been made to estimate and validate axonal pathways via a number of techniques, such as myelin stain, tract-tracing and diffusion MRI (dMRI). The three modalities have their own advantages and are complimentary to each other. From myelin stain data, we can infer rich in-plane information of axonal orientation at micro-scale. Tract-tracing data is considered as 'gold standard' to estimate trustworthy meso-scale pathways. dMRI currently is the only way to estimate global macro-scale pathways given further validation. We propose a framework to take advantage of these three modalities. Information of the three modalities is integrated to determine the optimal tractography parameters for dMRI fibers and identify cross-validated fiber bundles that are finally used to construct atlas. We demonstrate the effectiveness of the framework by a collection of experimental results.


Assuntos
Encéfalo/diagnóstico por imagem , Imagem de Difusão por Ressonância Magnética/métodos , Imagem de Tensor de Difusão/métodos , Bainha de Mielina , Algoritmos , Animais , Encéfalo/anatomia & histologia , Corantes , Conectoma/métodos , Processamento de Imagem Assistida por Computador/métodos , Macaca , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
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