An investigation of the phase locking index for measuring of interdependency of cortical source signals recorded in the EEG

The phase locking index (PLI) was introduced to quantify in a statistical sense the phase synchronization of two signals. It has been commonly used to process biosignals. In this article, we investigate the PLI for measuring the interdependency of cortical source signals (CSSs) recorded in the Electroencephalogram (EEG). To this end, we consider simple analytical models for the mapping of simulated CSSs into the EEG. For these models, the PLI is investigated analytically and through numerical simulations. An evaluation is made of the sensitivity of the PLI to the amount of crosstalk between the sources through biological tissues of the head. It is found that the PLI is a useful interdependency measure for CSSs, especially when the amount of crosstalk is small. Another common interdependency measure is the coherence. A direct comparison of both measures has not been made in the literature so far. We assess the performance of the PLI and coherence for estimation and detection purposes based on, respectively, a normalized variance and a novel statistical measure termed contrast. Based on these performance measures, it is found that the PLI is similar or better than the CM in most cases. This result is also confirmed through analysis of EEGs recorded from epileptic patients

Similarities and Differences Between Warped Linear Prediction and Laguerre Linear Prediction

Linear prediction has been successfully applied in many speech and audio processing systems. This paper presents the similarities and differences between two classes of linear prediction schemes, namely, Warped Linear Prediction (WLP) and Laguerre Linear Prediction (LLP). It is shown that both systems are closely related. In particular, we show that the LLP is in fact a WLP system where the optimization procedure is adapted such that the whitening property is automatically incorporated. The adaptation consists of a new linear constraint on the parameters. Furthermore, we show that an optimized WLP scheme where whitening is achieved by prefiltering before estimating the optimal coefficients results in a filter having all except the last reflection coefficient equal to those of the optimal LLP filter.

Key Extraction From General Nondiscrete Signals

We address the problem of designing optimal schemes for the generation of secure cryptographic keys from continuous noisy data. We argue that, contrary to the discrete case, a universal fuzzy extractor does not exist. This implies that in the continuous case, key extraction schemes have to be designed for particular probability distributions. We extend the known definitions of the correctness and security properties of fuzzy extractors. Our definitions apply to continuous as well as discrete variables. We propose a generic construction for fuzzy extractors from noisy continuous sources, using independent partitions. The extra freedom in the choice of discretization, which does not exist in the discrete case, is advantageously used to give the extracted key a uniform distribution. We analyze the privacy properties of the scheme and the error probabilities in a one-dimensional toy model with simplified noise. Finally, we study the security implications of incomplete knowledge of the source’s probability distribution P. We derive a bound on the min-entropy of the extracted key under the worst-case assumption, where the attacker knows P exactly.

BEDEUTUNGSMÖGLICHKEITEN VON ABRAXAS IN HERMANN HESSES 'DEMIAN'

Hermann Hesse fick med utvecklingsromanen Demian sitt litterära genombrott. I romanen spelar guden Abraxas en viktig roll. Abraxas har ett tupphuvud, kropp och armar från en människa och ormar istället för ben. Gudens lära inspirerar romanens protagonist att lära känna sig själv och påbörja en psykisk mognadsprocess. Denna mognadsprocess kallades av C.G. Jung för individuation och hans teorier om det mänskliga psyket påverkade sannolikt Hesses arbete med Demian. Syftet med denna uppsats är att undersöka olika möjligheter för betydelsen av Abraxas i Demian. En förståelse för Abraxas betydelse i Demian skulle kunna innebära att inflytandet av Jungs teorier på verket understryks. Analysen i denna uppsats visar att Abraxas förkroppsligar en sammansmältning av gott och ont, av Gud och Satan. Han är himlens och helvetets gud och de med honom associerade idéerna kan förstås som en kritik av kristendomen. Därutöver kan Abraxas även förstås som en symbol för individuationen. I detta arbete föreslås även ytterligare en tolkning av Abraxas, nämligen som symbol för verkande. Abraxas symboliserar alltså drivkraften att påbörja och genomföra individuationsprocessen. Denna nya tolkning av Abraxas som symbol för verkande och drivkraft förklarar också att romanens huvudperson orkar genomföra individuationen. Att stå öga mot öga med de egna svagheterna och att erkänna de egna dunkla begären är psykiskt påfrestande och vore inte möjligt utan egen drivkraft, vilken i Demian symboliseras av Abraxas. Dessa resultat understryker betydelsen av Jungs teorier för verket