ABSTRACT
The brain is a dynamic system that generates a broad repertoire of perceptual, motor, and cognitive states by the integration and segregation of different functional domains represented in large-scale brain networks. However, the fundamental mechanisms underlying brain network integration remain elusive. Here, for the first time to our knowledge, we found that in the resting state the brain visits few synchronization modes defined as clusters of temporally aligned functional hubs. These modes alternate over time and their probability of switching leads to specific temporal loops among them. Notably, although each mode involves a small set of nodes, the brain integration seems highly vulnerable to a simulated attack on this temporal synchronization mechanism. In line with the hypothesis that the resting state represents a prior sculpted by the task activity, the observed synchronization modes might be interpreted as a temporal brain template needed to respond to task/environmental demands .
Subject(s)
Brain Waves/physiology , Cerebral Cortex/diagnostic imaging , Cerebral Cortex/physiology , Connectome/methods , Magnetoencephalography/methods , Nerve Net/diagnostic imaging , Nerve Net/physiology , Adult , Female , Humans , Male , Young AdultABSTRACT
Bone repair/regeneration is usually investigated through X-ray computed microtomography (µCT) supported by histology of extracted samples, to analyse biomaterial structure and new bone formation processes. Magnetic resonance imaging (µMRI) shows a richer tissue contrast than µCT, despite at lower resolution, and could be combined with µCT in the perspective of conducting non-destructive 3D investigations of bone. A pipeline designed to combine µMRI and µCT images of bone samples is here described and applied on samples of extracted human jawbone core following bone graft. We optimized the coregistration procedure between µCT and µMRI images to avoid bias due to the different resolutions and contrasts. Furthermore, we used an Adaptive Multivariate Clustering, grouping homologous voxels in the coregistered images, to visualize different tissue types within a fused 3D metastructure. The tissue grouping matched the 2D histology applied only on 1 slice, thus extending the histology labelling in 3D. Specifically, in all samples, we could separate and map 2 types of regenerated bone, calcified tissue, soft tissues, and/or fat and marrow space. Remarkably, µMRI and µCT alone were not able to separate the 2 types of regenerated bone. Finally, we computed volumes of each tissue in the 3D metastructures, which might be exploited by quantitative simulation. The 3D metastructure obtained through our pipeline represents a first step to bridge the gap between the quality of information obtained from 2D optical microscopy and the 3D mapping of the bone tissue heterogeneity and could allow researchers and clinicians to non-destructively characterize and follow-up bone regeneration.
Subject(s)
Bone Regeneration/physiology , Bone and Bones/diagnostic imaging , Bone and Bones/physiology , Imaging, Three-Dimensional , Magnetic Resonance Imaging , X-Ray Microtomography , Aged , Calcification, Physiologic , Female , Humans , Male , Middle Aged , Multivariate Analysis , OsteogenesisABSTRACT
This article discusses the techniques and logic of the lower extremity evaluation of patients with possible neuromuscular disorders. Its emphasis is on the efficient development of a clinical database from which to draw inferences to probable pathologic diagnoses. As such, this article provides review material for the articles elsewhere in this issue regarding specialized examination techniques, differential diagnosis, and specific pathologies.
Subject(s)
Foot Diseases/diagnosis , Neurologic Examination/methods , Peripheral Nervous System Diseases/diagnosis , Podiatry/methods , Foot Diseases/physiopathology , Humans , Peripheral Nervous System Diseases/physiopathology , Physical Examination , United StatesABSTRACT
Quantitative sensory testing techniques have been developed to yield more consistent and objective measures of sensory deficits than can be obtained through the traditional clinical evaluation of the patient. At the same time, these measures are less invasive and uncomfortable than typical electrophysiologic studies. This article provides an overview of the principles of quantitative sensory testing, and discusses currently available instruments.
Subject(s)
Foot Diseases/diagnosis , Neurologic Examination/instrumentation , Peripheral Nervous System Diseases/diagnosis , Podiatry/instrumentation , Foot Diseases/physiopathology , Humans , Neurologic Examination/standards , Peripheral Nervous System Diseases/physiopathology , Sensitivity and Specificity , Sensory ThresholdsABSTRACT
To evaluate thiamine status in an urban adolescent population, we performed two investigations. In Study I, we compared whole blood thiamine levels in 101 healthy adolescents from varied racial backgrounds with those that had been obtained previously in 146 healthy white adults from a different geographic locale. Blood thiamine values were significantly lower in the adolescents as a group, but the differences were entirely due to the lower levels in the black adolescents. To explore further these differences (Study II), we compared thiamine status in 34 adolescents with that of their parents using measures of both whole blood thiamine content and of erythrocyte transketolase activity. White adolescents had significantly higher total whole blood thiamine values than black adolescents, and white parents had significantly higher thiamine values than black parents by both total whole blood assay and level of transketolase activity. There were no differences in thiamine status between adolescents and parents of the same race. Racial composition is an important variable to consider in population surveys of thiamine status.
