Graph theory and network modelling have been previously applied to characterize motor network structural topology in multiple sclerosis (MS). However, between‐group differences disclosed by graph analysis might be primarily driven by discrepancy in density, which is likely to be reduced in pathologic conditions as a consequence of macroscopic damage and fibre loss that may result in less streamlines properly traced. In this work, we employed the convex optimization modelling for microstructure informed tractography (COMMIT) framework, which, given a tractogram, estimates the actual contribution (or weight) of each streamline in order to optimally explain the diffusion magnetic resonance imaging signal, filtering out those that are implausible or not necessary. Then, we analysed the topology of this ‘COMMIT‐weighted sensory‐motor network’ in MS accounting for network density. By comparing with standard connectivity analysis, we also tested if abnormalities in network topology are still identifiable when focusing on more ‘quantitative’ network properties. We found that topology differences identified with standard tractography in MS seem to be mainly driven by density, which, in turn, is strongly influenced by the presence of lesions. We were able to identify a significant difference in density but also in network global and local properties when accounting for density discrepancy. Therefore, we believe that COMMIT may help characterize the structural organization in pathological conditions, allowing a fair comparison of connectomes which considers discrepancies in network density. Moreover, discrepancy‐corrected network properties are clinically meaningful and may help guide prognosis assessment and treatment choice. 相似文献
Little is known about the neural correlates of lower limbs position sense, despite the impact that proprioceptive deficits have on everyday life activities, such as posture and gait control. We used fMRI to investigate in 30 healthy right‐handed and right‐footed subjects the regional distribution of brain activity during position matching tasks performed with the right dominant and the left nondominant foot. Along with the brain activation, we assessed the performance during both ipsilateral and contralateral matching tasks. Subjects had lower errors when matching was performed by the left nondominant foot. The fMRI analysis suggested that the significant regions responsible for position sense are in the right parietal and frontal cortex, providing a first characterization of the neural correlates of foot position matching. 相似文献
To validate the HeadCount-2w questionnaire for estimation of 2-week soccer heading by comparison to daily electronic diary reporting over the same two-week period.
Design
Prospective observational study.
Methods
Adult amateur soccer players completed HeadCount-daily, comprising 14 daily at-home assessments of soccer play and heading via a tablet PC. Following the 14 day period, players completed HeadCount-2w, a web-based two-week-recall questionnaire on soccer and heading. intraclass correlation coefficient (ICC) was estimated between HeadCount-daily, the reference standard, and HeadCount-2w estimates of heading during the same 2-week period.
Results
53 participants (38 men) reported a mean of 24.36 (median = 11.76) headers during 2 weeks via HeadCount-daily and a mean of 38.34 (median = 15.0) headers for the same 2 weeks via HeadCount-2w. The ICC comparing 2-week heading from HeadCount-daily and HeadCount-2w was 0.85. Linear regression of the log-transformed Headcount-daily on HeadCount-2w data yielded a slope of 0.71 (p < 0.001; 95% CI 0.54–0.82), suggesting that heading tends to be over-estimated by HeadCount-2w relative to HeadCount-daily. Slope estimates for men (0.65) and women (0.71) were similar.
Conclusions
HeadCount, a self-administered web-based survey, is valid for self-reporting 2-week heading in adult amateur players, supporting its use in future research and as a simple and low-cost technique for exposure monitoring. 相似文献
Assess the prevalence of white matter microstructural changes in combat veterans, within the context of a highly matched control group comprising unexposed close relatives.
Methods
This prospective study had institutional review board approval, included written informed consent, and is HIPAA-compliant. Diffusion tensor imaging was analyzed in 16 male blast-exposed combat veterans of Operation Iraqi Freedom/Operation Enduring Freedom (mean age 31.0 years) and 18 unexposed males (mean age 30.4 years) chosen on the basis of a consanguineous relationship to a member of the subject group. Whole-brain voxel-based comparison of fractional anisotropy (FA) was performed using both group and individual analyses. Areas where effects on FA were detected were subsequently characterized by extracting radial diffusivity (RD), axial diffusivity (AD), and mean diffusivity (MD) from the regions of abnormal FA.
Results
Controls did not differ from veterans on any background demographic factor. In voxel-based group comparison, we identify high fractional anisotropy (FA) in veterans compared to controls (p?<?0.01). Within individual veterans, we find multiple areas of both abnormally high and low FA (p?<?0.01) in a heterogeneous distribution, consistent with multifocal traumatic axonal injury. In individualized analyses, low FA areas demonstrate high radial diffusivity, whereas high FA areas demonstrate low RD in both group and individual analyses.
Conclusions
Combat-related blast exposure is associated with microstructural white matter abnormalities, and the nature of the control group decreases the likelihood that the findings reflect underlying background differences. Abnormalities are heterogeneously distributed across patients, consistent with TAI, and include areas of low and high FA.