Impaired structural connectivity between dorsal attention network and pulvinar mediates the impact of premature birth on adult visual–spatial abilities

The dorsal attention network (DAN), including frontal eye fields and posterior parietal cortices, and its link with the posterior thalamus, contribute to visual–spatial abilities. Very premature birth impairs both visual–spatial abilities and cortico‐thalamic structural connectivity. We hypothesized that impaired structural DAN‐pulvinar connectivity mediates the effect of very premature birth on adult visual–spatial abilities. Seventy very premature (median age 26.6 years) and 57 mature born adults (median age 26.6 years) were assessed with cognitive tests and diffusion tensor imaging. Perceptual organization (PO) index of the Wechsler Adult Intelligence Scale‐III was used as a proxy for visual–spatial abilities, and connection probability maps in the thalamus, derived from probabilistic tractography from the DAN, were used as a proxy for DAN‐thalamic connectivity. Premature born adults showed decreases in both PO‐index and connection probability from DAN into the pulvinar, with both changes being positively correlated. Moreover, path analysis revealed that DAN‐pulvinar connectivity mediates the relationship between very premature birth and PO‐index. Results provide evidence for long‐term effects of very premature birth on structural DAN‐pulvinar connectivity, mediating the effect of prematurity on adult visual–spatial impairments. Data suggest DAN‐pulvinar connectivity as a specific target of prognostic and diagnostic procedures for visual–spatial abilities after premature birth

СОВРЕМЕННЫЕ ВОЗМОЖНОСТИ ФУНКЦИОНАЛЬНОЙ МАГНИТНО-РЕЗОНАНСНОЙ ТОМОГРАФИИ В НЕЙРОВИЗУАЛИЗАЦИИ

Functional MRI has now become one of the main methods of brain activity imaging. This is the only technique that allows you to analyze brain activity by studying the activation of the local blood flow of the cerebral cortex at rest or in response to any stimulus. Currently, fMRI is not widely used in routine clinical practice, although it has been successfully used in leading neurological and neurosurgical clinics, as well as in scientific research studies for brain activity evaluation. Main goal of using fMRI in clinical practice is preoperative mapping of the brain functions before neurosurgical interventions; however, there are other promising areas of fMRI. This review paper describes the technical aspects of the various fMRI techniques and discusses the possibilities of fMRI in different neurological diseases.Функциональная МРТ (ФМРТ) в настоящее время стала одной из основных методик визуализации мозговой деятельности. Это единственная методика, которая позволяет провести анализ деятельности мозга, изучив активацию локального кровотока коры мозга в покое или в ответ на какие-либо стимулы. В настоящее время фМРТ не получила широкого клинического применения, хотя успешно используется в ведущих неврологических и нейрохирургических клиниках, а также в научных исследованиях, изучающих мозговую деятельность. Наиболее часто в клинической практике фМРТ применяется для предоперационного картирования основных функций перед нейрохирургическими вмешательствами, однако существуют и другие перспективные направления использования фМРТ. В данной обзорной статье рассмотрены технические аспекты выполнения различных видов фМРТ и представлены возможности методики при различных неврологических заболеваниях

Thalamic nuclei segmentation from T1_1-weighted MRI: unifying and benchmarking state-of-the-art methods with young and old cohorts

The thalamus and its constituent nuclei are critical for a broad range of cognitive and sensorimotor processes, and implicated in many neurological and neurodegenerative conditions. However, the functional involvement and specificity of thalamic nuclei in human neuroimaging is underappreciated and not well studied due, in part, to technical challenges of accurately identifying and segmenting nuclei. This challenge is further exacerbated by a lack of common nomenclature for comparing segmentation methods. Here, we use data from healthy young (Human Connectome Project, 100 subjects) and older healthy adults, plus those with minor cognitive impairment and Alzheimer$'$s disease (Alzheimer$'$s Disease Neuroimaging Initiative, 540 subjects), to benchmark four state of the art thalamic segmentation methods for T1 MRI (FreeSurfer, HIPS-THOMAS, SCS-CNN, and T1-THOMAS) under a single segmentation framework. Segmentations were compared using overlap and dissimilarity metrics to the Morel stereotaxic atlas. We also quantified each method$'$s estimation of thalamic nuclear degeneration across Alzheimer$'$s disease progression, and how accurately early and late mild cognitive impairment, and Alzheimers disease could be distinguished from healthy controls. We show that HIPS-THOMAS produced the most effective segmentations of individual thalamic nuclei and was also most accurate in discriminating healthy controls from those with mild cognitive impairment and Alzheimer$'$s disease using individual nucleus volumes. This work is the first to systematically compare the efficacy of anatomical thalamic segmentation approaches under a unified nomenclature. We also provide recommendations of which segmentation method to use for studying the functional relevance of specific thalamic nuclei, based on their overlap and dissimilarity with the Morel atlas.Comment: 10 figures, 4 tables, 3 supplemental figures, 2 supplemental table

Altered metabolic-functional coupling in the epileptogenic network could predict surgical outcomes of mesial temporal lobe epilepsy

ObjectiveTo investigate the relationship between glucose metabolism and functional activity in the epileptogenic network of patients with mesial temporal lobe epilepsy (MTLE) and to determine whether this relationship is associated with surgical outcomes.Methods18F-FDG PET and resting-state functional MRI (rs-fMRI) scans were performed on a hybrid PET/MR scanner in 38 MTLE patients with hippocampal sclerosis (MR-HS), 35 MR-negative patients and 34 healthy controls (HC). Glucose metabolism was measured using 18F-FDG PET standardized uptake value ratio (SUVR) relative to cerebellum; Functional activity was obtained by fractional amplitude of low-frequency fluctuation (fALFF). The betweenness centrality (BC) of metabolic covariance network and functional network were calculated using graph theoretical analysis. Differences in SUVR, fALFF, BC and the spatial voxel-wise SUVR-fALFF couplings of the epileptogenic network, consisting of default mode network (DMN) and thalamus, were evaluated by Mann-Whitney U test (using the false discovery rate [FDR] for multiple comparison correction). The top ten SUVR-fALFF couplings were selected by Fisher score to predict surgical outcomes using logistic regression model.ResultsThe results showed decreased SUVR-fALFF coupling in the bilateral middle frontal gyrus (PFDR = 0.0230, PFDR = 0.0296) in MR-HS patients compared to healthy controls. Coupling in the ipsilateral hippocampus was marginally increased (PFDR = 0.0802) in MR-HS patients along with decreased BC of metabolic covariance network and functional network (PFDR = 0.0152; PFDR = 0.0429). With Fisher score ranking, the top ten SUVR-fALFF couplings in regions from DMN and thalamic subnuclei could predict surgical outcomes with the best performance being a combination of ten SUVR-fALFF couplings with an AUC of 0.914.ConclusionThese findings suggest that the altered neuroenergetic coupling in the epileptogenic network is associated with surgical outcomes of MTLE patients, which may provide insight into their pathogenesis and help with preoperative evaluation

Characterizing functional modules in the human thalamus: coactivation-based parcellation and systems-level functional decoding

The human thalamus relays sensory signals to the cortex and facilitates brain-wide communication. The thalamus is also more directly involved in sensorimotor and various cognitive functions but a full characterization of its functional repertoire, particularly in regard to its internal anatomical structure, is still outstanding. As a putative hub in the human connectome, the thalamus might reveal its functional profile only in conjunction with interconnected brain areas. We therefore developed a novel systems-level Bayesian reverse inference decoding that complements the traditional neuroinformatics approach towards a network account of thalamic function. The systems-level decoding considers the functional repertoire (i.e., the terms associated with a brain region) of all regions showing co-activations with a predefined seed region in a brain-wide fashion. Here, we used task-constrained meta-analytic connectivity-based parcellation (MACM-CBP) to identify thalamic subregions as seed regions and applied the systems-level decoding to these subregions in conjunction with functionally connected cortical regions. Our results confirm thalamic structure–function relationships known from animal and clinical studies and revealed further associations with language, memory, and locomotion that have not been detailed in the cognitive neuroscience literature before. The systems-level decoding further uncovered large systems engaged in autobiographical memory and nociception. We propose this novel decoding approach as a useful tool to detect previously unknown structure–function relationships at the brain network level, and to build viable starting points for future studies.Peer Reviewe

Toward a Common Terminology for the Thalamus

The wealth of competing parcellations with limited cross-correspondence between atlases of the human thalamus raises problems in a time when the usefulness of neuroanatomical methods is increasingly appreciated for modern computational analyses of the brain. An unequivocal nomenclature is, however, compulsory for the understanding of the organization of the thalamus. This situation cannot be improved by renewed discussion but with implementation of neuroinformatics tools. We adopted a new volumetric approach to characterize the significant subdivisions and determined the relationships between the parcellation schemes of nine most influential atlases of the human thalamus. The volumes of each atlas were 3d-reconstructed and spatially registered to the standard MNI/ICBM2009b reference volume of the Human Brain Atlas in the MNI (Montreal Neurological Institute) space (Mai and Majtanik, 2017). This normalization of the individual thalamus shapes allowed for the comparison of the nuclear regions delineated by the different authors. Quantitative cross-comparisons revealed the extent of predictability of territorial borders for 11 area clusters. In case of discordant parcellations we re-analyzed the underlying histological features and the original descriptions. The final scheme of the spatial organization provided the frame for the selected terms for the subdivisions of the human thalamus using on the (modified) terminology of the Federative International Programme for Anatomical Terminology (FIPAT). Waiving of exact individual definition of regional boundaries in favor of the statistical representation within the open MNI platform provides the common and objective (standardized) ground to achieve concordance between results from different sources (microscopy, imaging etc.)

Tratti temperamentali e cognizione sociale: uno studio di risonanza magnetica cerebrale

Negli ultimi decenni il temperamento ha acquisito via via maggiore considerazione nello spettro dei disturbi affettivi. Degni di nota sono in particolare il temperamento ciclotimico ed ipertimico, considerati fattori di rischio per tali disturbi. Lo studio mira ad individuare differenze neurofisiologiche tra individui con caratteri temperamentali diversi. Il focus che abbiamo scelto per questa ricerca è la teoria della mente (ToM), poiché ha dimostrato precedentemente, di essere influenzata sia nei disturbi affettivi, che nei domini temperamentali (temperamenti diversi influenzeranno diversamente lo sviluppo della ToM). A tale scopo è stato scelto un task ToM per la raccolta di scansioni fMRI. Nello specifico sono state scelte le animazioni di Happè e Frith, che, sfruttando il principio teorizzato da Heider e Simmel, evocano nell’osservatore stati interni complessi legati alla cognizione sociale. Nella seconda parte dello studio abbiamo eseguito un test a questionario di autovalutazione chiamato TEMPS-M, in modo da poter riconoscere nei diversi soggetti i diversi livelli dei domini temperamentali. La TEMPS-M è la versione tradotta e riadattata in italiano da Sampogna (2019), del questionario abbreviato TEMPS-A. Entrambi fanno riferimento alla divisione dei domini temperamentali categorizzati da Hagop Akiskal: ipertimico, ciclotimico, depressivo, irritabile ed ansioso. Infine, abbiamo valutato la correlazione di determinati tratti temperamentali con l’attivazione neurale evidenziata durante la raccolta di scansione fMRI con task di cognizione sociale. Attraverso cluster correction (con cluster threshold impostato a p<0,005) siamo stati in grado di evidenziare una correlazione positiva tra l’attivazione del talamo e la sottoscala ipertimica. L’area significativa rilevata ha un’estensione di 149 voxel. Questo studio, coerentemente con le evidenze degli ultimi decenni, sottolinea la relazione tra il grado temperamentale ipertimico ed il talamo, un’area densamente interconnessa con tutto l’encefalo veicolante funzioni di tipo cognitivo, affettivo, percettivo, mnemotico, esecutivo e di altro tipo

Quasi-periodic patterns of brain intrinsic activity coordinate the functional connections in humans

The brain is a complex self-organizing biophysical system and intrinsically very active. How such intrinsic activity organizes the brain in humans is widely being studied during resting-state using functional magnetic resonance imaging (rsfMRI) and the functional connectivity (FC) metric. FC, calculated as the Pearson correlation between rsfMRI timeseries from different brain areas, indicates coherent activity on average over time, and can reflect some spatial aspects of the brain’s intrinsic organization. For example, based on the FC profile of each area, the cerebral cortex can be parcellated into a few resting-state networks (RSNs) or exhibit a few functional connectivity gradients (FCGs). Brain is a complex system and exhibits varied dynamic spatiotemporal regimes of coherent activity, which are still poorly understood. A subset of such regimes should be giving rise to FC, yet they might entail significantly insightful aspects about the brain’s self-organizing processes, which cannot be captured by FC. Among such dynamic regimes is the quasi-periodic pattern (QPP), obtained by identifying and averaging similar ~20s-long segments of rsfMRI timeseries. QPP involves a cycle of activation and deactivation of different areas with different timings, such that the overall activity within QPP resembles RSNs and FCGs, suggesting QPP might be contributing to FC. To robustly detect multiple QPPs, method improvements were implemented and three primary QPPs were thoroughly characterized. Within these QPPs activity propagates along the functional gradients at the cerebral cortex and most subcortical regions, in a well-coordinated way, because of the consistencies and synchronies across all brain regions which reasonably accord with the consensus on the structural connections. Nuanced timing differences between regions and the closed flow of activity throughout the brain suggest drivers for these patterns. When three QPPs are removed from rsfMRI timeseries, FC within and particularly between RSNs remarkably reduces, illustrating their dominant contribution. Together, our results suggest a few recurring spatiotemporal patterns of intrinsic activity might be dominantly coordinating the functional connections across the whole brain and serving self-organization. These intrinsic patterns possibly interact with the external tasks, affecting performance, or might provide more sensitive biomarkers in certain disorders and diseases.Ph.D

Receptor architecture of the macaque monkey superior parietal lobule

The macaque monkey superior parietal lobule (SPL) is part of a neuronal network involved in the integration of information from visual and somatosensory cortices for execution of reaching and grasping movements. The cytoarchitecture of areas V6, V6Ad, V6Av, PE, PEc, PEci and PGm of the SPL has been described, but little is known about their receptor architectonic organization, although receptor analyses not only provide information concerning brain structure, but also crucial insights into its functional organization. Quantitative in vitro receptor autoradiography was applied to analyze the distribution patterns of 15 different receptors for glutamate, GABA, acetylcholine, serotonin, dopamine and adenosine in the SPL of three adult male Macaca fascicularis monkeys. For each area, mean (averaged over all cortical layers) receptor densities were visualized as a receptor fingerprint of each area. Multivariate analyses were conducted to detect clusters of areas according to the degree of (dis)similarity of their receptor organization. Differences in regional and laminar receptor distribution patterns confirm the location and extent of areas V6, V6Ad, V6Av, PE, PEc, PEci and PGm as found in cytoarchitectonical and functional studies. Receptor densities are higher in supra- than in infragranular layers of SPL areas, with the exception of kainate, M2, and adenosine receptors, which reach highest values in layers V-VI. The hierarchical cluster analysis shows a principal segregation of SPL areas from the primary sensory cortices. Areas PEc, PEci and PGm cluster with posterior cingulate area 31. Area V6Av clusters with visual V6, and V6Ad with MIP, while area PE with somatosensory area 2. These results are in accordance with the fact that V6Av contains more cells responsive to visual stimuli than does V6Ad, whereas the opposite holds true for cells responsive to somatosensory stimuli. They further emphasize the special receptor architecture of posterior parietal areas involved in reaching and grasping