Epilepsy investigated non-invasively using Elecroencephalography (EEG) and Magnetoencephalography (MEG)

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Volume conductor modeling of the human head for electroencephalography (EEG) used in epilepsy

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Visualizing simulated electrical fields from electroencephalography and transcranial electric brain stimulation: a comparative evaluation

pre-printElectrical activity of neuronal populations is a crucial aspect of brain activity. This activity is not measured directly but recorded as electrical potential changes using head surface electrodes (electroencephalogram - EEG). Head surface electrodes can also be deployed to inject electrical currents in order to modulate brain activity (transcranial electric stimulation techniques) for therapeutic and neuroscientific purposes. In electroencephalography and noninvasive electric brain stimulation, electrical fields mediate between electrical signal sources and regions of interest (ROI). These fields can be very complicated in structure, and are influenced in a complex way by the conductivity profile of the human head. Visualization techniques play a central role to grasp the nature of those fields because such techniques allow for an effective conveyance of complex data and enable quick qualitative and quantitative assessments. The examination of volume conduction effects of particular head model parameterizations (e.g., skull thickness and layering), of brain anomalies (e.g., holes in the skull, tumors), location and extent of active brain areas (e.g., high concentrations of current densities) and around current injecting electrodes can be investigated using visualization. Here, we evaluate a number of widely used visualization techniques, based on either the potential distribution or on the current-flow. In particular, we focus on the extractability of quantitative and qualitative information from the obtained images, their effective integration of anatomical context information, and their interaction. We present illustrative examples from clinically and neuroscientifically relevant cases and discuss the pros and cons of the various visualization techniques

Automated long-term EEG analysis to localize the epileptogenic zone

OBJECTIVE: We investigated the performance of automatic spike detection and subsequent electroencephalogram (EEG) source imaging to localize the epileptogenic zone (EZ) from long-term EEG recorded during video-EEG monitoring. METHODS: In 32 patients, spikes were automatically detected in the EEG and clustered according to their morphology. The two spike clusters with most single events in each patient were averaged and localized in the brain at the half-rising time and peak of the spike using EEG source imaging. On the basis of the distance from the sources to the resection and the known patient outcome after surgery, the performance of the automated EEG analysis to localize the EZ was quantified. RESULTS: In 28 out of the 32 patients, the automatically detected spike clusters corresponded with the reported interictal findings. The median distance to the resection in patients with Engel class I outcome was 6.5 and 15 mm for spike cluster 1 and 27 and 26 mm for cluster 2, at the peak and the half-rising time of the spike, respectively. Spike occurrence (cluster 1 vs. cluster 2) and spike timing (peak vs. half-rising) significantly influenced the distance to the resection (p < 0.05). For patients with Engel class II, III, and IV outcomes, the median distance increased to 36 and 36 mm for cluster 1. Localizing spike cluster 1 at the peak resulted in a sensitivity of 70% and specificity of 100%, positive prediction value (PPV) of 100%, and negative predictive value (NPV) of 53%. Including the results of spike cluster 2 led to an increased sensitivity of 79% NPV of 55% and diagnostic OR of 11.4, while the specificity dropped to 75% and the PPV to 90%. SIGNIFICANCE: We showed that automated analysis of long-term EEG recordings results in a high sensitivity and specificity to localize the epileptogenic focus

Hermeneutics and Nature

This paper contributes to the on-going research into the ways in which the humanities transformed the natural sciences in the late Eighteenth and early Nineteenth Centuries. By investigating the relationship between hermeneutics -- as developed by Herder -- and natural history, it shows how the methods used for the study of literary and artistic works played a crucial role in the emergence of key natural-scientific fields, including geography and ecology

Realistic flight conditions on ground: new research facility for cabin ventilation

A new full-scale test bench was developed and set up at the German Aerospace Center in Göttingen to experimentally analyze novel ventilation approaches for aircraft under realistic thermodynamic boundary conditions. The new ground-based test rig represents a modern twin-aisle cabin layout characteristic for long-haul airliners. In addition to having a realistic cabin geometry, it also facilitates the experimental simulation of thermodynamic boundary conditions to study the performance of alternative ventilation concepts for different fight phases (e.g., climbing or cruising). The implemented fuselage elements as well as the foor are temperature controllable. Using this kind of mantle heating/cooling system allows dynamic changes of inner surface temperatures in a range covering the operationally relevant temperature and time scales. With this experimental set-up, a complete fight scenario (i.e., taxiing, climbing, cruising and descent) can be simulated thermodynamically.Thermal manikins were used during the studies to simulate the passenger's heat impact experimentally. Latest measurement techniques comprising the acquisition of fow velocities, fuid temperatures as well as surface temperatures were used. Based on these data, integral quantities like the mean temperature stratifcation and mean velocity levels near the manikins, the heat removal efciency as well as the predicted mean vote and the percentage of dissatisfed passengers were calculated to score the ventilation concepts in terms of passenger comfort for two diferent operational scenarios under steady boundary conditions

Comparison of two ceiling-based ventilation strategies for twin-aisle aircraft cabins

Two novel, ceiling-module integrated ventilation concepts are presented and experimentally analysed in a twin-aisle long-range cabin mock-up for different flight phases simulated by varied thermodynamic boundary conditions. Generally, the different supply techniques of LMCV and MJV reveal many similarities regarding mean flow fields and temperature distributions. However, local differences regarding higher flow velocities are found in the aisle region for MJV. A more detailed analysis based on studies with different mass flow ratios will be discussed at the conference. Moreover, the results regarding the analysis of the air quality level will be presented at the conference. Hereto, tracer gas measurements are carried out at the moment in order to determine local and global ventilation efficiencies