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Abstract Trial-to-trial variability and spontaneous activity of cortical recordings have been suggested to reflect intrinsic noise. This view is currently challenged by mounting evidence for structure in these phenomena: Trial-to-trial variability decreases following stimulus onset and can be predicted by previous spontaneous activity. This spontaneous activity is similar in magnitude and structure to evoked activity and can predict decisions. Allof the observed neuronal properties described above can be accounted for, at an abstract computational level, by the sampling-hypothesis, according to which response variability reflects stimulus uncertainty. However, a mechanistic explanation at the level of neural circuit dynamics is still missing.
In this study, we demonstrate that all of these phenomena can be accounted for by a noise-free self-organizing recurrent neural network model (SORN). It combines spike-timing dependent plasticity (STDP) and homeostatic mechanisms in a deterministic network of excitatory and inhibitory McCulloch-Pitts neurons. The network self-organizes to spatio-temporally varying input sequences.
We find that the key properties of neural variability mentioned above develop in this model as the network learns to perform sampling-like inference. Importantly, the model shows high trial-to-trial variability although it is fully deterministic. This suggests that the trial-to-trial variability in neural recordings may not reflect intrinsic noise. Rather, it may reflect a deterministic approximation of sampling-like learning and inference. The simplicity of the model suggests that these correlates of the sampling theory are canonical properties of recurrent networks that learn with a combination of STDP and homeostatic plasticity mechanisms.
Author Summary Neural recordings seem very noisy. If the exact same stimulus is shown to an animal multiple times, the neural response will vary. In fact, the activity of a single neuron shows many features of a stochastic process. Furthermore, in the absence of a sensory stimulus, cortical spontaneous activity has a magnitude comparable to the activity observed during stimulus presentation. These findings have led to a widespread belief that neural activity is indeed very noisy. However, recent evidence indicates that individual neurons can operate very reliably and that the spontaneous activity in the brain is highly structured, suggesting that much of the noise may in fact be signal. One hypothesis regarding this putative signal is that it reflects a form of probabilistic inference through sampling. Here we show that the key features of neural variability can be accounted for in a completely deterministic network model through self-organization. As the network learns a model of its sensory inputs, the deterministic dynamics give rise to sampling-like inference. Our findings show that the notorious variability in neural recordings does not need to be seen as evidence for a noisy brain. Instead it may reflect sampling-like inference emerging from a self-organized learning process.
Langsam aber sicher fragt man sich, ob es überhaupt noch Sinn macht, aktuelle Enthüllungen über Geheimdienstaktivitäten als Aufhänger zu benutzen. Man hat sich schon so daran gewöhnt, dass es im Hintergrundrauschen untergeht. Aber versuchen wir es trotzdem noch mal: Hey, wer von den geneigten Lesern war auf der WikiLeaks Webseite? Oder The Pirate Bay? Ruft jemand „ja“ vor seinem Rechner? Sehr gut. Sagt „hallo“, denn ihr wurdet vom britischen Geheimdienst (GCHQ) und/oder der NSA erfasst. Snowden lässt grüßen, und wieder einmal fühlt man sich ein wenig unsicherer online. Aber keine Sorge, Angela Merkel und Francois Hollande haben einen Plan. Und die EU hat auch einen...
The administration of intravenous fluid to critically ill patients is one of the most common but also one of the most fiercely debated interventions in intensive care medicine. During the past decade, a number of important studies have been published which provide clinicians with improved knowledge regarding the timing, the type and the amount of fluid they should give to their critically ill patients. However, despite the fact that many thousands of patients have been enrolled in these trials of alternative fluid strategies, consensus remains elusive and practice is widely variable. Early adequate resuscitation of patients in shock followed by a restrictive strategy may be associated with better outcomes. Colloids such as modern hydroxyethyl starch are more effective than crystalloids in early resuscitation of patients in shock, and are safe when administered during surgery. However, these colloids may not be beneficial later in the course of intensive care treatment and should best be avoided in intensive care patients who have a high risk of developing acute kidney injury. Albumin has no clear benefit over saline and is associated with increased mortality in neurotrauma patients. Balanced fluids reduce the risk of hyperchloraemic acidosis and possibly kidney injury. The use of hypertonic fluids in patients with sepsis and acute lung injury warrants further investigation and should be considered experimental at this stage. Fluid therapy impacts relevant patient-related outcomes. Clinicians should adopt an individualized strategy based on the clinical scenario and best available evidence. One size does not fit all.
The primary objective of What on Earth is a Ruling Party in a Multiparty Democracy? is to provoke thought and thereby stimulate debate. To this end, provocatively, this collection of topical issues ranges from 'The place of the miniskirt in sociocultural development' to 'Which citizen in Zambia should not take part in (partisan) politics?' The Author, Mubanga E Kashoki, is a Professor of African Languages at the institute of Economic and Social Research in the University of Zambia.
What happened in Cyprus? The economic consequences of the last communist government in Europe
(2014)
This paper reviews developments in the Cypriot economy following the introduction of the euro on 1 January 2008 and leading to the economic collapse of the island five years later. The main cause of the collapse is identified with the election of a communist government in February 2008, within two months of the introduction of the euro, and its subsequent choices for action and inaction on economic policy matters. The government allowed a rapid deterioration of public finances, and despite repeated warnings, damaged the country's creditworthiness and lost market access in May 2011. The destruction of the island's largest power station in July 2011 subsequently threw the economy into recession. Together with the intensification of the euro area crisis in the summer and fall of 2011, these events weakened the banking system which was vulnerable due to its exposure in Greece. Rather than deal with its fiscal crisis, the government secured a loan from the Russian government that allowed it to postpone action until after the February 2013 election. Rather than protect the banking system, losses were imposed on banks and a campaign against them was coordinated and used as a platform by the communist party for the February 2013 election. The strategy succeeded in delaying resolution of the crisis and avoiding short-term political cost for the communist party before the election, but also in precipitating a catastrophe right after the election.
On 23 July 2014, the U.S. Securities and Exchange Commission (SEC) passed the “Money Market Reform: Amendments to Form PF ,” designed to prevent investor runs on money market mutual funds such as those experienced in institutional prime funds following the bankruptcy of Lehman Brothers. The present article evaluates the reform choices in the U.S. and draws conclusions for the proposed EU regulation of money market funds.
Research results confirm the existence of various forms of international tax planning by multinational firms. Prominent examples for firms employing tax avoidance strategies are Amazon, Google and Starbucks. Increasing availability of administrative data for Europe has enabled researchers to study behavioural responses of European multinationals to taxation. The present paper summarizes what we can learn from these recent studies in general and about German multinationals in particular.
BACKGROUND: Micro-RNAs (miRNA) are attributed to the systems biological role of a regulatory mechanism of the expression of protein coding genes. Research has identified miRNAs dysregulations in several but distinct pathophysiological processes, which hints at distinct systems-biology functions of miRNAs. The present analysis approached the role of miRNAs from a genomics perspective and assessed the biological roles of 2954 genes and 788 human miRNAs, which can be considered to interact, based on empirical evidence and computational predictions of miRNA versus gene interactions.
RESULTS: From a genomics perspective, the biological processes in which the genes that are influenced by miRNAs are involved comprise of six major topics comprising biological regulation, cellular metabolism, information processing, development, gene expression and tissue homeostasis. The usage of this knowledge as a guidance for further research is sketched for two genetically defined functional areas: cell death and gene expression. Results suggest that the latter points to a fundamental role of miRNAs consisting of hyper-regulation of gene expression, i.e., the control of the expression of such genes which control specifically the expression of genes.
CONCLUSIONS: Laboratory research identified contributions of miRNA regulation to several distinct biological processes. The present analysis transferred this knowledge to a systems-biology level. A comprehensible and precise description of the biological processes in which the genes that are influenced by miRNAs are notably involved could be made. This knowledge can be employed to guide future research concerning the biological role of miRNA (dys-) regulations. The analysis also suggests that miRNAs especially control the expression of genes that control the expression of genes.
Wettbewerbsrecht der GKV
(2014)
Seit inzwischen 20 Jahren führt der Gesetzgeber in die Binnenordnung der Gesetzlichen Krankenversicherung Wettbewerbselemente ein. Ausgangspunkt ist die Kassenwahlfreiheit der Versicherten. Die Krankenkassen agieren dadurch immer stärker als Wettbewerber um Versicherte. Seit einigen Jahren ist der Rechtsrahmen dieses Wettbewerbs in der Diskussion und auch prozessual und politisch umstritten. Inwieweit das allgemeine Kartellrecht, konkret die Fusionskontrolle, oder das allgemeine Lauterkeitsrecht Anwendung finden soll, ist noch nicht abschließend geklärt. Weniger grundsätzliche Probleme bereitet hingegen das Vergaberecht. Der Beitrag beschreibt die sich im Fluss befindliche Rechtsgrundlage des GKV-Wettbewerbsrechts in ihrer bisherigen Entwicklung und auf dem Stand von 2013.
Der Deutsche Juristentag 2012 ließ begutachten, wie der Wettbewerb in der Gesetzlichen Krankenversicherung zu regeln sei. Der vorliegende Beitrag ist als Begleitaufsatz hierzu erschienen. Er spürt den Motiven des Gesetzgebers und den theoretischen und konzeptionellen Gründen für Wettbewerb nach, um daraus Antworten auf die Frage nach der Wettbewerbsregulierung im Gesundheitswesen zu entwickeln. Sein Ergebnis ist, dass die spezifische Funktion von Wettbewerb innerhalb des sozialrechtlichen Krankenversicherungssystems ein spezifisches Regulierungsrecht erfordert. Dies ist gegenüber einer generellen Zuordnung dieses Sozialsystems zum allgemeinen Wettbewerbs- und Kartellrecht vorzugswürdig. Außerdem wird die Zuordnung zu den Sozialgerichten befürwortet.