In this paper, we provide evidence for functional asymmetries in forward and backward connections that
define hierarchical architectures in the brain. We exploit the fact that modulatory or nonlinear influences of
one neuronal system on another (i.e., effective connectivity) entail coupling between different frequencies.
Functional asymmetry in forward and backward connections was addressed by comparing dynamic causal
models of MEG responses induced by visual processing of normal and scrambled faces.We compared models
with and without nonlinear (between-frequency) coupling in both forward and backward connections.
Bayesian model comparison indicated that the best model had nonlinear forward and backward connections.
Using the best model we then quantified frequency-specific causal influences mediating observed spectral
responses. We found a striking asymmetry between forward and backward connections; in which high
(gamma) frequencies in higher cortical areas suppressed low (alpha) frequencies in lower areas. This
suppression was significantly greater than the homologous coupling in the forward connections.
Furthermore, exactly the asymmetry was observed when we examined face-selective coupling (i.e., coupling
under faces minus scrambled faces). These results highlight the importance of nonlinear coupling among
brain regions and point to a functional asymmetry between forward and backward connections in the human
brain that is consistent with anatomical and physiological evidence from animal studies. This asymmetry is
also consistent with functional architectures implied by theories of perceptual inference in the brain, based
on hierarchical generative models.
This paper presents models for search behavior and provides experimental evidence that behavioral heterogeneity in search is linked to heterogeneity in individual preferences. Observed search behavior is more consistent with a new model that assumes dynamic updating of utility reference points than with models that are based on expected-utility maximization. Specifically, reference point updating and loss aversion play a role for more than a third of the population. The findings are of practical relevance as well as of interest for researchers who incorporate behavioral heterogeneity into models of dynamic choice behavior in, for example, consumer economics, labor economics, finance, and decision theory.
There is an extensive literature claiming that it is often di*cultnto make use of arbitrage opportunities in *nancial markets. Thisnpaper provides a new reason why existing arbitrage opportunitiesnmight not be seized. We consider a world with short-lived securities,nno short-selling constraints and no transaction costs. We show thatnto exploit all existing arbitrage opportunities, traders should paynattention to all *nancial markets simultaneously. It gives a generalnresult stating that failure to do so will leave some arbitrage oppor-ntunies unexploited with probability one.
This paper shows that a stock market is evolutionary stable if andnonly if stocks are evaluated by expected relative dividends. Any othernmarket can be invaded by portfolio rules that will gain market wealthnand hence change the valuation. In the model the valuation of assetsnis given by the wealth average of the portfolio rules in the market. Thenwealth dynamics is modelled as a random dynamical system. Necessary and sufficient conditions are derived for the evolutionary stabilitynof portfolio rules when (relative) dividend payoffs form a stationarynMarkov process. These local stability conditions lead to a unique evolutionary stable strategy according to which assets are evaluated bynexpected relative dividends.
Tobin (1958) has argued that in the face of potential capital losses on bonds it is nreasonable to hold cash as a means to transfer wealth over time. It is shown that this assertion cannot be sustained taking into account the evolution of wealth of cash holders versus non cash holders. Cash holders will be driven out of the market in the long run by traders who only use a (risky) long-lived asset to transfer wealth.
Der Benediktinerorden hat schon früh erstaunlich ausgefeilte Führungs- und Kontrollstrukturen entwickelt und
etabliet. Wie sich Unternehmen davon inspirieren lassen können, zeigen die Autoren des folgenden Beitrages.
This paper investigates the merger wave hypothesis for the US and the UK employing a Markov regime-switching model. Using quarterly data covering the last 30 years, for the US, we identify the beginning of a merger wave in the mid 1990s but not the much-discussed 1980s merger wave. We argue that the latter finding can be ascribed to the refined methods of inference offered by the Gibbs sampling approach. As opposed to the US, mergers in the UK exhibit multiple waves, with activity surging in the early 1970s and the late 1980s.
Speaker: Mirco Musolesi University College London, UK Date: Thursday, March 23, 2017 Place: USI Lugano Campus, room SI-008, informatics building (Via G. Buffi 13) Time: 9:30 ...
Auditorio campus di Lugano Martedì 21 marzo ore 17:30 Prosegue il prossimo martedì 21 marzo, alle ore 17:30 nell auditorio del campus di Lugano, il ciclo rectoverso , la serie di conferenze nel corso delle quali il Rettore dell USI Prof. Boas Erez mette a tema incontro dopo incontro ...
It is common in econometric applications that several hypothesis tests are carried out at the same time. The problem then becomes how to decide whichnhypotheses to reject, accounting for the multitude of tests.nThe classical approach is to control the familywise error rate (FWE), that is, thenprobability of one or more false rejections. But when thennumber of hypotheses under consideration is large, control of the FWE can become too demanding. As a result, the number of false hypotheses rejected may be small or even zero. This suggests replacingncontrol of the FWE by a more liberal measure. To this end,nwe review a number of proposals from the statistical literature.nWe briefly discuss how these procedures apply to the general problem of model selection. A simulation study and two empirical applications illustrate the methods.
