Extraction of network topology from multi-electrode recordings: is there a small-world effect?
- The simultaneous recording of the activity of many neurons poses challenges for multivariate data analysis. Here, we propose a general scheme of reconstruction of the functional network from spike train recordings. Effective, causal interactions are estimated by fitting generalized linear models on the neural responses, incorporating effects of the neurons’ self-history, of input from other neurons in the recorded network and of modulation by an external stimulus. The coupling terms arising from synaptic input can be transformed by thresholding into a binary connectivity matrix which is directed. Each link between two neurons represents a causal influence from one neuron to the other, given the observation of all other neurons from the population. The resulting graph is analyzed with respect to small-world and scale-free properties using quantitative measures for directed networks. Such graph-theoretic analyses have been performed on many complex dynamic networks, including the connectivity structure between different brain areas. Only few studies have attempted to look at the structure of cortical neural networks on the level of individual neurons. Here, using multi-electrode recordings from the visual system of the awake monkey, we find that cortical networks lack scale-free behavior, but show a small, but significant small-world structure. Assuming a simple distance-dependent probabilistic wiring between neurons, we find that this connectivity structure can account for all of the networks’ observed small-world-ness. Moreover, for multi-electrode recordings the sampling of neurons is not uniform across the population. We show that the small-world-ness obtained by such a localized sub-sampling overestimates the strength of the true small-world structure of the network. This bias is likely to be present in all previous experiments based on multi-electrode recordings.
Wiwi news : newsletter of the Faculty of Economics and Business Administration
Staging a Supplement : Judge Adam, Advocate “Liebling” and William, the Detective
- Legal practice is based on something that is not only an integral part of it and complements it, but also puts it into question generally. The compulsion to argue and reach decisions in a legal trial clarifies simultaneously that all forms of decision are inapproprate, unreasonable, and can be recreated in an entirely new manner [to suit the needs of the trial]. This is the legalistic supplement in the spirit of Jacques Derrida. The legal truth is supplemented by other forms of media such as drama, film and literature, which are able to stage scenes that cannot be experienced in a real life legal world, but – as no legal official would deny – are an integral part of the trial and verdict procedure.
EFL quarterly : an E-Finance Lab publication
Newsletter / House of Finance, Goethe-Universität Frankfurt
- Das House of Finance hat im Sommer 2008 sein Gebäude bezogen. Unter seinem Dach führt das House of Finance drei Abteilungen aus den Fachbereichen Rechtswissenschaft und Wirtschaftswissenschaften der Goethe-Universität sowie sechs rechtlich selbstständige Institute – darunter auch das E-Finance Lab - zusammen. Neben den traditionellen Aufgaben in der Forschung und Lehre verfolgt das House of Finance das Vorhaben, die Ergebnisse der Forschung für die Praxis und auch für den Finanzplatz Deutschland nutzbar zu machen. Als ein Element dieses Wissenstransfers veröffentlicht das House of Finance die „Newsletter“. Der „Newsletter“ gibt Auskunft über - drei aktuelle Forschungsergebnisse, - die Entwicklungen in der Executive Education, - die neuesten Veröffentlichungen der im House of Finance ansässigen Wissenschaftler, - den Veranstaltungskalender. Der Newsletter umfasst jeweils 16 Seiten und erscheint vierteljährlich in englischer Sprache.
FIAS Scientific Report
Measuring shear viscosity using correlations
- Measurements of transverse momentum fluctuations can be used to determine the shear viscosity . We use current data to estimate the viscosity-to-entropy ratio in the range from 0.08 to 0.3, and discuss how future measurements can reduce this uncertainty.
ProtoSociology : an international journal of interdisciplinary research
- ProtoSociology is an interdisciplinary journal which crosses the borders of philosophy, social sciences, and their corresponding disciplines. Each issue concentrates on a specific topic taken from the current discussion to which scientists from different fields contribute the results of their research. ProtoSociology is further a project that examines the nature of mind, language and social systems. In this context theoretical work has been done by investigating such theoretical concepts like interpretation and (social) action, globalization, the global world-system, social evolution, and the sociology of membership. Our purpose is to initiate and enforce basic research on relevant topics from different perspectives and traditions.
News / Center for Financial Studies
- CFSnewsletter is a documentation of past, present and future CFS activities in the fields of research, executive development and events. Printed versions of all issues published since 1997 can be ordered free of charge. To download the latest issues, you need ADOBE Acrobat Reader. Contact: Lut De Moor Phone: +49-(0)69-798-30060 Fax: +49-(0)69-798-30077 media_contact (AT) ifk-cfs.de
Market structure, capital regulation and bank risk taking
Reinhard H. Schmidt
- This paper discusses the effect of capital regulation on the risk taking behavior of commercial banks. We first theoretically show that capital regulation works differently in different market structures of banking sectors. In lowly concentrated markets, capital regulation is effective in mitigating risk taking behavior because banks' franchise values are low and banks have incentives to pursue risky strategies in order to increase their franchise values. If franchise values are high, on the other hand, the effect of capital regulation on bank risk taking is ambiguous as banks lack those incentives. We then test the model predictions on a cross-country sample including 421 commercial banks from 61 countries. We find that capital regulation is effective in mitigating risk taking only in markets with a low degree of concentration. The results remain robust after accounting for financial sector development, legal system effciency, and for other country and bank-specific characteristics. Keywords: Banks, market structure, risk shifting, franchise value, capital regulation