Pompeu Fabra University

About: Pompeu Fabra University is a education organization based out in Barcelona, Spain. It is known for research contribution in the topics: Population & Gene. The organization has 8093 authors who have published 23570 publications receiving 858431 citations. The organization is also known as: Universitat Pompeu Fabra & UPF.

Heterogeneous transmission mechanism: monetary policy and financial fragility in the eurozone

Abstract: The eurozone economic activity and banking sector have shown substantial fragility over the last years with remarkable country heterogeneity. Using detailed data on lending conditions and standards, we analyse – along several key dimensions of heterogeneity – how financial fragility has affected the transmission mechanism of the single eurozone monetary policy. The analysis shows that the monetary transmission mechanism is time-varying and influenced by the financial fragility of the sovereigns, banks, firms and households. The impact of monetary policy on aggregate output is stronger during the financial crisis, especially in countries facing increased sovereign financial distress. This amplification mechanism, moreover, operates through the credit channel, both the bank lending and the non-financial borrower balance-sheet channels. Our results suggest that the bank-lending channel has been to a large extent neutralized by the ECB non-standard monetary policy interventions, but the policy framework until the end of 2011 was insufficient to overcome credit availability problems stemming from deteriorated firm net worth and risk conditions, especially for small firms in countries under stress. — Matteo Ciccarelli, Angela Maddaloni and Jose-Luis Peydro

The Fittest versus the Flattest: Experimental Confirmation of the Quasispecies Effect with Subviral Pathogens

Abstract: The “survival of the fittest” is the paradigm of Darwinian evolution in which the best-adapted replicators are favored by natural selection. However, at high mutation rates, the fittest organisms are not necessarily the fastest replicators but rather are those that show the greatest robustness against deleterious mutational effects, even at the cost of a low replication rate. This scenario, dubbed the “survival of the flattest”, has so far only been shown to operate in digital organisms. We show that “survival of the flattest” can also occur in biological entities by analyzing the outcome of competition between two viroid species coinfecting the same plant. Under optimal growth conditions, a viroid species characterized by fast population growth and genetic homogeneity outcompeted a viroid species with slow population growth and a high degree of variation. In contrast, the slow-growth species was able to outcompete the fast species when the mutation rate was increased. These experimental results were supported by an in silico model of competing viroid quasispecies.

A model of grid cells based on a twisted torus topology.

Abstract: The grid cells of the rat medial entorhinal cortex (MEC) show an increased firing frequency when the position of the animal correlates with multiple regions of the environment that are arranged in regular triangular grids. Here, we describe an artificial neural network based on a twisted torus topology, which allows for the generation of regular triangular grids. The association of the activity of pre-defined hippocampal place cells with entorhinal grid cells allows for a highly robust-to-noise calibration mechanism, suggesting a role for the hippocampal back-projections to the entorhinal cortex.

Fungal evolutionary genomics provides insight into the mechanisms of adaptive divergence in eukaryotes.

Abstract: Fungi are ideal model organisms for dissecting the genomic bases of adaptive divergence in eukaryotes. They have simple morphologies and small genomes, occupy contrasting, well-identified ecological niches and tend to have short generation times, and many are amenable to experimental approaches. Fungi also display diverse lifestyles, from saprotrophs to pathogens or mutualists, and they play extremely important roles in both ecosystems and human activities, as wood decayers, mycorrhizal fungi, lichens, endophytes, plant and animal pathogens, and in fermentation or drug production. We review here recent insights into the patterns and mechanisms of adaptive divergence in fungi, including sources of divergence, genomic variation and, ultimately, speciation. We outline the various ecological sources of divergent selection and genomic changes, showing that gene loss and changes in gene expression and in genomic architecture are important adaptation processes, in addition to the more widely recognized processes of amino acid substitution and gene duplication. We also review recent findings regarding the interspecific acquisition of genomic variation and suggesting an important role for introgression, hybridization and horizontal gene transfers (HGTs). We show that transposable elements can mediate several of these genomic changes, thus constituting important factors for adaptation. Finally, we review the consequences of divergent selection in terms of speciation, arguing that genetic incompatibilities may not be as widespread as generally thought and that pleiotropy between adaptation and reproductive isolation is an important route of speciation in fungal pathogens.

The impact of bilingualism on the executive control and orienting networks of attention

Abstract: The main objective of this article is to provide new evidence regarding the impact of bilingualism on the attentional system. We approach this goal by assessing the effects of bilingualism on the executive and orienting networks of attention. In Experiment 1, we compared young bilingual and monolingual adults in a numerical version of the Stroop task, which allowed the assessment of the executive control network. We observed more efficient performance in the former group, which showed both reduced Stroop Interference and larger Stroop Facilitation Effects relative to the latter. Conversely, Experiment 2, conducted with a visual cueing task in order to assess the orienting network, revealed similar Cueing Facilitation and Inhibition (Inhibition of Return – IOR) Effects for both groups of speakers. The implications of the results of these two experiments for the origin and boundaries of the bilingual impact on the attentional system are discussed.