Clinical connectome fingerprints of cognitive decline

Brain connectome fingerprinting is rapidly rising as a novel influential field in brain network analysis. Yet, it is still unclear whether connectivity fingerprints could be effectively used for mapping and predicting disease progression from human brain data. We hypothesize that dysregulation of brain activity in disease would reflect in worse subject identification. We propose a novel framework, Clinical Connectome Fingerprinting, to detect individual connectome features from clinical populations. We show that “clinical fingerprints” can map individual variations between elderly healthy subjects and patients with mild cognitive impairment in functional connectomes extracted from magnetoencephalography data. We find that identifiability is reduced in patients as compared to controls, and show that these connectivity features are predictive of the individual Mini-Mental State Examination (MMSE) score in patients. We hope that the proposed methodology can help in bridging the gap between connectivity features and biomarkers of brain dysfunction in large-scale brain networks

Mutations in the SPAST gene causing hereditary spastic paraplegia arerelated to global topological alterations in brain functional networks

Aim: Our aim was to describe the rearrangements of the brain activity related to genetic mutations in the SPAST gene. Methods: Ten SPG4 patients and ten controls underwent a 5 min resting state magnetoencephalography recording and neurological examination. A beamformer algorithm reconstructed the activity of 90 brain areas. The phase lag index was used to estimate synchrony between brain areas. The minimum spanning tree was used to estimate topological metrics such as the leaf fraction (a measure of network integration) and the degree divergence (a measure of the resilience of the network against pathological events). The betweenness centrality (a measure to estimate the centrality of the brain areas) was used to estimate the centrality of each brain area. Results: Our results showed topological rearrangements in the beta band. Specifically, the degree divergence was lower in patients as compared to controls and this parameter related to clinical disability. No differences appeared in leaf fraction nor in betweenness centrality. Conclusion: Mutations in the SPAST gene are related to a reorganization of the brain topology

The structural connectome constrains fast brain dynamics

Brain activity during rest displays complex, rapidly evolving patterns in space and time. Structural connections comprising the human connectome are hypothesized to impose constraints on the dynamics of this activity. Here, we use magnetoencephalography (MEG) to quantify the extent to which fast neural dynamics in the human brain are constrained by structural connections inferred from diffusion MRI tractography. We characterize the spatio-temporal unfolding of whole-brain activity at the millisecond scale from source-reconstructed MEG data, estimating the probability that any two brain regions will significantly deviate from baseline activity in consecutive time epochs. We find that the structural connectome relates to, and likely affects, the rapid spreading of neuronal avalanches, evidenced by a significant association between these transition probabilities and structural connectivity strengths (r = 0.37, p<0.0001). This finding opens new avenues to study the relationship between brain structure and neural dynamics

A night of sleep deprivation alters brain connectivity and affects specific executive functions

Sleep is a fundamental physiological process necessary for efficient cognitive functioning especially in relation to memory consolidation and executive functions, such as attentional and switching abilities. The lack of sleep strongly alters the connectivity of some resting-state networks, such as the default mode network and attentional network. In this study, by means of magnetoencephalography (MEG) and specifc cognitive tasks, we investigated how brain topology and cognitive functioning are affected by 24 h of sleep deprivation (SD). Thirty-two young men underwent resting-state MEG recording and evaluated in letter cancellation task (LCT) and task switching (TS) before and after SD. Results showed a worsening in the accuracy and speed of execution in the LCT and a reduction of reaction times in the TS, evidencing thus a worsening of attentional but not of switching abilities. Moreover, we observed that 24 h of SD induced large-scale rearrangements in the functional network. These findings evidence that 24 h of SD is able to alter brain connectivity and selectively affects cognitive domains which are under the control of different brain network

Micromechanical Characterization of Complex Polypropylene Morphologies by HarmoniX AFM

This paper examines the capability of the HarmoniX Atomic Force Microscopy (AFM) technique to draw accurate and reliable micromechanical characterization of complex polymer morphologies generally found in conventional thermoplastic polymers. To that purpose, injection molded polypropylene samples, containing representative morphologies, have been characterized by HarmoniX AFM. Mapping and distributions of mechanical properties of the samples surface are determined and analyzed. Effects of sample preparation and test conditions are also analyzed. Finally, the AFM determination of surface elastic moduli has been compared with that obtained by indentation tests, finding good agreement among the results

Multiscale mechanical characterization of iPP injection molded samples

Mechanical characterizations at different length scales represent a very intriguing possibility for correlating the fine internal morphologies with the macroscopic properties of a polymer material. In this work, molded samples of isotactic polypropylene obtained by injection molding in different processing conditions have been characterized on different lengths scales. The developed morphologies characterized by optical and atomic force microscopy reveal a complex multilayer morphology with globular elements, fibrils and spherulites, from the surface to the sample core. A multiscale mechanical characterization has been performed by Dynamic Mechanical Analysis (DMA), micro indentation and by HarmoniX Atomic Force Microscopy (AFM) tests, from millimeter to nanometer scale. Results show that along sample thickness, well organized and oriented structures (i.e. fibrils) characterized by higher values of mechanical modulus coexist with less organized structures (globules) characterized by mechanical properties closer to the quiescent amorphous phase. Intermediate elasticity is found in the central part of the sample, where well developed spherulitic structures are characterized by both higher crystallinity and lower level of orientation. A good agreement among the relative experimental results has been found, confirming the good complementarity among these techniques for a complete multi-scale sample characterization

Fast mold surface temperature evolution: Challenges and opportunities

Fast mold temperature evolution allows obtaining injection molded parts with lower filling pressure, better surface finishing, more accurate surface replication and reduced frozen-in orientation. Recently proposed, thin heating devices, with very low thermal inertia, located just below the mold cavity surface, allow obtaining high surface temperature during filling and low surface temperature during cooling stage. Several tests have been carried out injecting isotactic polypropylene into a rectangular cavity with the aim of analyzing the effects of heating temperature and heating time (equal or larger to the filling time) on both part quality and process evolution. As far as the part quality is concerned, a relevant improvement of the surface micro features replication and a lower orientation level have been attained by increasing heating temperature and time. From the point of view of the process, a significant reduction of filling pressure and pressure drops have been reached by increasing the mold surface temperature. The cycle time increases when the surface heating time increases. However, this increase has been found not much different from the surface heating time, if thin heating devices located at a short distance from the mold surface are adopted. Some secondary effects on the pressure evolutions related to the in-mold cooling and solidification have been also observed during the process and have been discussed with reference to the heating elements activity

Fast mold surface temperature evolution: Relevance of asymmetric surface heating for morphology of iPP molded samples

It is widely accepted that mold temperature has a strong effect on the amount of molecular orientation and morphology developed in a non-isothermal flowing melt. In this work, this effect was investigated in fast and asymmetric thermal conditions. Therefore, a well-characterized isotactic polypropylene was injected in a rectangular mold cavity conditioned by a purpose developed thin electric heater. Temperature evolution on the mold surface influences the cooling rates near the surface that, in turn, reduces flow stresses and facilitates molecular relaxation. Moreover, asymmetrical thermal conditions have a strong influence on the melt flow field by changing its distribution along the cavity thickness. As a consequence, the morphology distribution of the molded samples was asymmetric and showed complex and peculiar features. It was accurately characterized by optical microscopy and FESEM analysis and compared with the orientation distribution obtained by birefringence measurements