A continuous mapping of sleep states through association of EEG with a mesoscale cortical model

Here we show that a mathematical model of the human sleep cycle can be used to obtain a detailed description of electroencephalogram (EEG) sleep stages, and we discuss how this analysis may aid in the prediction and prevention of seizures during sleep. The association between EEG data and the cortical model is found via locally linear embedding (LLE), a method of dimensionality reduction. We first show that LLE can distinguish between traditional sleep stages when applied to EEG data. It reliably separates REM and non-REM sleep and maps the EEG data to a low-dimensional output space where the sleep state changes smoothly over time. We also incorporate the concept of strongly connected components and use this as a method of automatic outlier rejection for EEG data. Then, by using LLE on a hybrid data set containing both sleep EEG and signals generated from the mesoscale cortical model, we quantify the relationship between the data and the mathematical model. This enables us to take any sample of sleep EEG data and associate it with a position among the continuous range of sleep states provided by the model; we can thus infer a trajectory of states as the subject sleeps. Lastly, we show that this method gives consistent results for various subjects over a full night of sleep and can be done in real time

Why do presidents fail? political leadership and the Argentine crisis (1999–2001)

This article explores why Argentine president Fernando de la Rúa (1999–2001) failed to govern and the factors that prevented him from completing his constitutional mandate. This study draw on current literature about leadership. We argue that President De la Rúa’s ineffective performance was characteristic of an inflexible tendency towards unilateralism, isolationism, and an inability to compromise and persuade. Moreover, we examine how de la Rúas performance, in the context of severe political and economic constraints, discouraged cooperative practices among political actors, led to decision-making paralysis, and ultimately to a crisis of governance.This work seeks to make four contributions. First, it conceptualizes political leadership by providing an analytical framework that integrates individual action, institutional resources and constraints, and policy context, thus filling a gap in the literature. Second, it explains the importance of effective leadership in building up and maintaining multiparty coalitions in presidential systems. Third, it complements existing institutional approaches to improve our understanding of a new type of instability in Latin America: the failure of more than a dozen of presidents to complete their constitutional mandates. Fourth, it analyzes the way political and economic variables interact in times of crisis