EEG–fMRI of idiopathic and secondarily generalized epilepsies

We used simultaneous EEG and functional MRI (EEG–fMRI) to study generalized spike wave activity (GSW) in idiopathic and secondary generalized epilepsy (SGE). Recent studies have demonstrated thalamic and cortical fMRI signal changes in association with GSW in idiopathic generalized epilepsy (IGE). We report on a large cohort of patients that included both IGE and SGE, and give a functional interpretation of our findings. Forty-six patients with GSW were studied with EEG–fMRI; 30 with IGE and 16 with SGE. GSW-related BOLD signal changes were seen in 25 of 36 individual patients who had GSW during EEG–fMRI. This was seen in thalamus (60%) and symmetrically in frontal cortex (92%), parietal cortex (76%), and posterior cingulate cortex/precuneus (80%). Thalamic BOLD changes were predominantly positive and cortical changes predominantly negative. Group analysis showed a negative BOLD response in the cortex in the IGE group and to a lesser extent a positive response in thalamus. Thalamic activation was consistent with its known role in GSW, and its detection in individual cases with EEG–fMRI may in part be related to the number and duration of GSW epochs recorded. The spatial distribution of the cortical fMRI response to GSW in both IGE and SGE involved areas of association cortex that are most active during conscious rest. Reduction of activity in these regions during GSW is consistent with the clinical manifestation of absence seizures

Significant reductions in human visual gamma frequency by the gaba reuptake inhibitor tiagabine revealed by robust peak frequency estimation

The frequency of visual gamma oscillations is determined by both the neuronal excitation-inhibition balance and the time constants of GABAergic processes. The gamma peak frequency has been linked to sensory processing, cognitive function, cortical structure, and may have a genetic contribution. To disentangle the intricate relationship among these factors, accurate and reliable estimates of peak frequency are required. Here, a bootstrapping approach that provides estimates of peak frequency reliability, thereby increasing the robustness of the inferences made on this parameter was developed. The method using both simulated data and real data from two previous pharmacological MEG studies of visual gamma with alcohol and tiagabine was validated. In particular, the study by Muthukumaraswamy et al. [] (Neuropsychopharmacology 38(6):1105-1112), in which GABAergic enhancement by tiagabine had previously demonstrated a null effect on visual gamma oscillations, contrasting with strong evidence from both animal models and very recent human studies was re-evaluated. After improved peak frequency estimation and additional exclusion of unreliably measured data, it was found that the GABA reuptake inhibitor tiagabine did produce, as predicted, a marked decrease in visual gamma oscillation frequency. This result demonstrates the potential impact of objective approaches to data quality control, and provides additional translational evidence for the mechanisms of GABAergic transmission generating gamma oscillations in humans. Hum Brain Mapp, 2016. © 2016 Wiley Periodicals, Inc

Causal hierarchy within the thalamo-cortical network in spike and wave discharges

Background: Generalised spike wave (GSW) discharges are the electroencephalographic (EEG) hallmark of absence seizures, clinically characterised by a transitory interruption of ongoing activities and impaired consciousness, occurring during states of reduced awareness. Several theories have been proposed to explain the pathophysiology of GSW discharges and the role of thalamus and cortex as generators. In this work we extend the existing theories by hypothesizing a role for the precuneus, a brain region neglected in previous works on GSW generation but already known to be linked to consciousness and awareness. We analysed fMRI data using dynamic causal modelling (DCM) to investigate the effective connectivity between precuneus, thalamus and prefrontal cortex in patients with GSW discharges. Methodology and Principal Findings: We analysed fMRI data from seven patients affected by Idiopathic Generalized Epilepsy (IGE) with frequent GSW discharges and significant GSW-correlated haemodynamic signal changes in the thalamus, the prefrontal cortex and the precuneus. Using DCM we assessed their effective connectivity, i.e. which region drives another region. Three dynamic causal models were constructed: GSW was modelled as autonomous input to the thalamus (model A), ventromedial prefrontal cortex (model B), and precuneus (model C). Bayesian model comparison revealed Model C (GSW as autonomous input to precuneus), to be the best in 5 patients while model A prevailed in two cases. At the group level model C dominated and at the population-level the p value of model C was ∼1. Conclusion: Our results provide strong evidence that activity in the precuneus gates GSW discharges in the thalamo-(fronto) cortical network. This study is the first demonstration of a causal link between haemodynamic changes in the precuneus - an index of awareness - and the occurrence of pathological discharges in epilepsy. © 2009 Vaudano et al

Optimal tuning of the lateral-dynamics parameters for aerial vehicles with bounded lateral force

This letter shows for the first time why it is important and how to optimize the gains of a position controller on board of a fully-actuated aerial vehicle with bounded lateral force, via an auto-tuning approach. In such vehicles, most of the control authority is expressed along a principal thrust direction, while along lateral directions smaller forces can be exploited to achieve full-pose tracking. The nonlinear and hard to model interplay between the constraint imposed on the lateral force and the gains of the position controller is overcome by employing the OPTIM-tune calibration method. Several experimental tests, performed fully autonomously during flight, clearly show the practicability and benefits of the approach

The Effect of Twisted Wire Configuration on the Stability of External Fixator: A Biomechanical Study

The Ilizarov fixator is a type of external fixator that is used to treat patients who have suffered injuries from accidents, bone shortening, or nonunion of the bone. The principle behind the Ilizarov fixator is that thin wires (called Kirschner wires) are used to support the bones and connect them to framed rings. Before being fastened to the rings, the wires are tensioned and drilled through the bones. This study suggests using a new parallel wires configuration at the same level on the same ring and two revised versions, which are divergent and convergent models, and compare them with standard wires, 60 angle wires model. All models were designed using SolidWorks, a computer-aided design (CAD) software, and then analyzed in four conditions (axial compression, medial bending, posterior bending, and torsion) with Finite Element Analysis (FEA) using Ansys Workbench 2020 R2. Mechanical testing was conducted to validate the FEA results, A simple model consisting of a single ring, two K-wires, and polylactic acid (PLA) cylinders was utilized in a tensile test. It has been concluded from the results that the parallel model and its improvement have higher stiffness to axial compression, medial bending, and torsion, but a lower posterior bending stiffness, except the divergent model with 8-hole separation which has a relatively acceptable stiffness for posterior bending

A novel robust hexarotor capable of static hovering in presence of propeller failure

This letter presents a novel open source design of the Y-shaped hexarotor Unammend Aerial Vehicle (UAV), and proves both in theory and real experiments its robustness to the failure of any of its propellers. An intuitive geometrical interpretation of UAV static hovering ability is presented, through which the robustness of different coplanar/collinear hexarotor designs is analyzed. Following the presented geometrical interpretation, we also show the conditions that allow the Star-shaped hexarotor to be robust to the failure of some of its propellers, while showing its structural incapability to static hover in the case of the failure of at least one of the propellers. Finally, the efficiency of the Y-shaped and Star-shaped hexarotors are tested experimentally, and conclusions on the advantages and disadvantages of the two designs are drawn

Design of multirotor aerial vehicles: A taxonomy based on input allocation

This paper reviews the effect of multirotor aerial vehicle designs on their abilities in terms of tasks and system properties. We propose a general taxonomy to characterize and describe multirotor aerial vehicles and their designs, which we apply exhaustively on the vast literature available. Thanks to the systematic characterization of the designs, we exhibit groups of designs having the same abilities in terms of achievable tasks and system properties. In particular, we organize the literature review based on the number of atomic actuation units and we discuss global properties arising from their choice and spatial distribution in the mechanical designs. Finally, we provide a discussion on the common traits of the designs found in the literature and the main open and future problems

Recurrence Quantification Analysis of Dynamic Brain Networks

Evidence suggests that brain network dynamics is a key determinant of brain function and dysfunction. Here we propose a new framework to assess the dynamics of brain networks based on recurrence analysis. Our framework uses recurrence plots and recurrence quantification analysis to characterize dynamic networks. For resting-state magnetoencephalographic dynamic functional networks (dFNs), we have found that functional networks recur more quickly in people with epilepsy than healthy controls. This suggests that recurrence of dFNs may be used as a biomarker of epilepsy. For stereo electroencephalography data, we have found that dFNs involved in epileptic seizures emerge before seizure onset, and recurrence analysis allows us to detect seizures. We further observe distinct dFNs before and after seizures, which may inform neurostimulation strategies to prevent seizures. Our framework can also be used for understanding dFNs in healthy brain function and in other neurological disorders besides epilepsy.Comment: 77 pages, 11 figures; note: the acknowledgments section is the most complete in this arxiv version (compared to the published version in EJN

Enhancing the Ilizarov Apparatus: Mechanical Stiffness

The Ilizarov system is a form of external fixation device utilized by medical professionals to aid patients who have sustained injuries from accidents, bone shortening, or nonunion of the bone. The device is fixed onto the long bone of the patient and is adjusted according to the nature of the injury. Ilizarov's techniques are minimal invasiveness, not aggressive, spare tissues and involve little blood loss. It consists of wires that are secured to a modular circular frame and then tightened. The Ilizarov fixator is a valuable tool for treating acute fractures, especially in cases where there is bone loss and compromised soft tissue. Several studies have aimed to improve the effectiveness of Ilizarov fixation through modifications to its frame components, such as ring diameter, transosseous element diameter, ring separation, transosseous element count in each ring, and number of rings, as well as the type of transosseous element employed, including wires, full-pins, or half-pins. Furthermore, positioning of transosseous elements at the correct crossing angle without damaging the nerves and vessels while considering the intricacy of bone deformities. Recent advancements in Ilizarov fixation will be thoroughly reviewed in this manuscript, with a particular focus on improving the stiffness of the entire frame. The main objective of this review is to pinpoint the optimal configurations, with a particular focus on stiffness, in order to foster stability and ensure a successful recuperation

Anaemia among clinically well under-fives attending a community health centre in Venda, Limpopo Province

Background. Anaemia has been reported to affect 20 - 75% of children in South Africa. The range suggests the effects that geography, health, and socio-economic status can have on the observed prevalence of anaemia within a specific community. Our objective was to investigate the prevalence of anaemia in children aged under 5 presenting for well-child examinations at a community health centre in Thohoyandou, Limpopo Province. Design. A cross-sectional observational study was carried out in June and July 2007. Caregivers participated in a brief interview where demographic, health and nutritional information was collected. A blood sample was collected from each child, and haemoglobin levels were assessed with a point-of-care haemoglobin testing system. Anaemia was defined as having a haemoglobin valu