Neuronal adaptation effects in decision making

Recently, there has been an increased interest on the neural mechanisms underlying perceptual decision making. However, the effect of neuronal adaptation in this context has not yet been studied. We begin our study by investigating how adaptation can bias perceptual decisions. We considered behavioral data from an experiment on high-level adaptation-related aftereffects in a perceptual decision task with ambiguous stimuli on humans. To understand the driving force behind the perceptual decision process, a biologically inspired cortical network model was used. Two theoretical scenarios arose for explaining the perceptual switch from the category of the adaptor stimulus to the opposite, nonadapted one. One is noise-driven transition due to the probabilistic spike times of neurons and the other is adaptation-driven transition due to afterhyperpolarization currents. With increasing levels of neural adaptation, the system shifts from a noise-driven to an adaptation-driven modus. The behavioral results show that the underlying model is not just a bistable model, as usual in the decision-making modeling literature, but that neuronal adaptation is high and therefore the working point of the model is in the oscillatory regime. Using the same model parameters, we studied the effect of neural adaptation in a perceptual decision-making task where the same ambiguous stimulus was presented with and without a preceding adaptor stimulus. We find that for different levels of sensory evidence favoring one of the two interpretations of the ambiguous stimulus, higher levels of neural adaptation lead to quicker decisions contributing to a speed–accuracy trade off.

Using qualia information to identify lexical semantic classes in an unsupervised clustering task

Acquiring lexical information is a complex problem, typically approached by relying on a number of contexts to contribute information for classification. One of the first issues to address in this domain is the determination of such contexts. The work presented here proposes the use of automatically obtained FORMAL role descriptors as features used to draw nouns from the same lexical semantic class together in an unsupervised clustering task. We have dealt with three lexical semantic classes (HUMAN, LOCATION and EVENT) in English. The results obtained show that it is possible to discriminate between elements from different lexical semantic classes using only FORMAL role information, hence validating our initial hypothesis. Also, iterating our method accurately accounts for fine-grained distinctions within lexical classes, namely distinctions involving ambiguous expressions. Moreover, a filtering and bootstrapping strategy employed in extracting FORMAL role descriptors proved to minimize effects of sparse data and noise in our task.

Diversity of staphylococcal cassette chromosome mec elements in predominant methicillin-resistant Staphylococcus aureus clones in a small geographic area.

Recent population genetic studies suggest that staphylococcal cassette chromosome mec (SCCmec) was acquired much more frequently than previously thought. In the present study, we aimed to investigate the diversity of SCCmec elements in a local methicillin-resistant Staphylococcus aureus (MRSA) population. Each MRSA isolate (one per patient) recovered in the Vaud canton of Switzerland from January 2005 to December 2008 was analyzed by the double-locus sequence typing (DLST) method and SCCmec typing. DLST analysis indicated that 1,884/2,036 isolates (92.5%) belong to four predominant clones. As expected from the local spread of a clone, most isolates within clones harbored an identical SCCmec type. However, three to seven SCCmec types have been recovered in every predominant DLST clone, suggesting that some of these elements might have been acquired locally. This pattern could also be explained by distinct importations of related isolates into the study region. The addition of a third highly variable locus to further increase the discriminatory power of typing as well as epidemiological data suggested that most ambiguous situations were explained by the second hypothesis. In conclusion, our study showed that even if the acquisition of new SCCmec elements at a local level likely occurs, it does not explain all the diversity observed in the study region.

Sovereign Risk, Anonymous Markets, and the Effects of Globalization

The goal of this paper is to study the e¤ects of globalization on the workings of financial markets. We adopt a "technological" view of globalization, which consists of an exogenous reduction in the cost of shipping goods across di¤erent regions of the world. We model financial markets where agents anonymously trade securities issued by every other agent in the world. In the absence of frictions, we show how globalization creates trade opportunities among residents of different regions of the world, thereby raising welfare. In the presence of sovereign risk, however, there emerge two crucial interactions between trade among residents within a region and trade among residents of di¤erent regions. First, the more residents within a region trade with each other, the more they can trade with residents of other regions. Second, the possibility of trade with residents of other regions sometimes leads a government to not enforce payments by its residents, destroying trade opportunities among residents within the region. The net effect on welfare of this process of creation and destruction of trade opportunities is ambiguous. We argue that there are no policies governments can take to avoid the negative effects of globalization on trade among domestic residents. In a dynamic extension, we analyze how our results are a¤ected by reputational considerations.

Excess Entry, Ambiguity Seeking, and Competence: An Experimental Investigation

Excess entry refers to the high failure rate of new entrepreneurial ventures. Economic explanations suggest 'hit and run' entrants and risk-seeking behavior. A psychological explanation is that people (entrepreneurs) are overconfident in their abilities (Camerer & Lovallo, 1999). Characterizing entry decisions as ambiguous gambles, we alternatively suggest following Heath and Tversky (1991) that people seek ambiguity when the source of uncertainty is related to their competence. Overconfidence, as such, plays no role. This hypothesis is confirmed in an experimental study that also documents the phenomenon of reference group neglect. Finally, we emphasize the utility that people gain from engaging in activities that contribute to a sense of competence. This is an important force in economic activity that deserves more explicit attention.

WH-Constructions in Cape Verdean Creole

This dissertation concerns two types of wh-constructions – interrogative and relative clauses – of Cape Verdean Creole (CVC), a Portuguese-based Creole language spoken on the archipelago of Cape Verde, specifically the variety spoken on Santiago Island, in the coast of West Africa. Chapter 2 focus on some aspects of the syntax of CVC, claiming that the possibilities of S-V inversion are very limited and that verbs stay in Vº, except for the Present tense form of the copula verb e ‘to be’, which is the spell out of the formal feature [Present] of T. It is proposed that CVC exhibits a clause functional structure that is similar to English: [CP [TP [NegP [AspP [VP … ]]]]]. In this chapter, it is also suggested that a non Split-CP, based on the formal features [±D, ±V, ±Q, ±Wh, ±T], correctly accounts for the distribution of the complementizers in CVC. Chapter 3 presents the wh-question formation strategies exhibited by CVC, showing that some of them involve Move, while others do not. Considering CVC data, it is said that the language has two clausal typing processes: an ambiguous complementizer ki ([±Q, ±Wh]), whose checking domain is strictly local; and an unambiguous complementizer Ø ([+Q, +Wh]), whose checking domain is not strictly local. The first one derives fronted wh-questions and the second one accounts for wh-in- -situ. Chapter 4 describes the relativization strategies displayed by CVC, focusing on the fact that PP pied-piping is ruled out and that resumption is possible both inside and outside syntactic islands. It is suggested a revision of Bianchi’s (2002a) head raising analysis for the structure of relative clauses. Chapter 5 discusses the properties of the defective copy strategy ([wh[+PL] … el]) and presents evidence in favor of a distinction between this type of wh-strategy and resumption ([wh[+PL] … es]). It is argued that the language requires an overt pronominal form (3SG) to occur in the complement position of the preposition because CVC types the clause with a complementizer ki [uCat +D] and does not allow for preposition incorporation. The set of formal features of the lower copy is ‘shrinked’, i.e. the features are deleted but not erased, being accessible to PF. This analysis of the defective copy xiv strategy predicts that it only applies to PPs and that it is an autonomous process involving wh-movement, which is distinct from resumption.

Female-biased mortality in experimentally parasitized Alpine Swift Apus melba nestlings

1. Sex-biased mortality in adult vertebrates is often attributed to lower immunocompetence and higher parasite susceptibility of males. Although sex-specific mortality has also been reported during growth, the importance of sex-specific immunocompetence and parasite susceptibility in explaining male-biased mortality remains ambiguous in growing individuals because of potentially confounding sources of mortality such as sexual dimorphism. 2. Here, we investigated sex-specific susceptibility to the blood-sucking louse fly Crataerina melbae and sex differences in cell-mediated immunity in a bird species that is sexually monomorphic both in size and plumage coloration at the nestling stage, the Alpine Swift, Apus melba. 3. For this purpose, we manipulated ectoparasite loads by adding or removing flies to randomly chosen nests in two years, and injected nestlings with mitogenic phytohaemagglutinin (PHA) in another year. 4. There were no significant differences between male and female offspring in immune response towards PHA, parasite load, and parasite-induced decrease in growth rate. Secondary sex ratios were however biased toward males in parasitized broods, and this was explained by a greater mortality of females in parasitized than deparasitized broods. 5. Our findings are in contrast to the widely accepted hypothesis that males suffer a greater cost of parasitism. We discuss alternative hypotheses accounting for female-specific mortality.

Estudio comparativo de las estructuras genitales del macho en el género Pseudocentron (Hymenoptera, Megachilidae)

Comparative study of the structures of male genitalia in Pseudocentron species (Hymenoptera, Megachilidae). Male genitalia of twenty two species of Pseudocentron Mitchell, 1934 belonging to seven subgenera are analysed. The diagnostic characters are described and illustrated. The study shows that the male genitalia provides diagnostic characters at generic, subgeneric and specific levels.

Espécies de cigarrinhas (Hemiptera, Cicadellidae, Cicadellinae) em pomares de citros da região de Bebedouro, SP, com descrição de uma espécie nova de Acrogonia Stål

Sharpshooter leafhoppers (Hemiptera, Cicadellidae, Cicadellinae) in citrus groves of the area of Bebedouro, SP, with description of a new species of Acrogonia Stål. Sixteen species of Cicadellidae, subfamily Cicadellinae, were collected and identified: 11 of the tribe Cicadellini and five of the tribe Proconiini. The ten most common species, together with a new species, are characterized based on external morphology and male genitalia: Acrogonia citrina Marucci & Cavichioli sp. nov.; Bucephalogonia xanthophis (Berg, 1879); Dilobopterus costalimai Young, 1977; Ferrariana trivittata (Signoret, 1854); Hortensia similis (Walker, 1851); Macugonalia cavifrons (Stål, 1862); M. leucomelas (Walker, 1851); Oncometopia facialis (Signoret, 1854); Plesiommata corniculata Young, 1977 and P. mollicella (Fowler, 1900). The leafhopper samples were collected in citrus groves and in adjacent habitats (woods, swamp, cultivable plain, spontaneous vegetation of the grove, coffee crop and sugarcane) at the counties of Bebedouro and Monte Azul Paulista and in the district of Turvínia. The collecting methods were: insect net, yellow sticky cards, portable suction trap and Malaise trap. Identification keys were elaborated for the 16 species. There is a great diversity of Cicadellinae species in the citric groves. In the three areas sampled, it was collected a larger number of species of the tribe Cicadellini than of the tribe Proconiini. In the Bebedouro area, the vector species of Xylella fastidiosa, A. citrina sp. nov., B. xanthophis, D. costalimai and O. facialis, were collected in the citrus groves and in all adjacent habitats.

Revisão do gênero Mecocephala Dallas, 1851 (Heteroptera, Pentatomidae)

Revision of the genus Mecocephala Dallas, 1851 (Heteroptera, Pentatomidae). The genus Mecocephala Dallas, 1851 is revised, and some taxonomic and geographical distribution data are evaluated. The following species are considered to belong to this genus: M. acuminata Dallas, 1851 = M. holmbergi Pirán, 1969 syn. nov., M. curculionoides Pirán, 1959, M. bonariensis sp. nov., M. magna sp. nov., M. maldonadensis sp. nov., and M. zikani sp. nov.; their distribution is restricted to southern Neotropical Region. Other species, formerly placed in Mecocephala, are considered, respectively: M. rubripes Berg, 1894 incertae sedis, M. darwini Kirkaldy, 1909 incertae sedis, M. atra Bergroth, 1914 incertae sedis, Paramecocephala uruguayensis (Pirán, 1970) comb. nov., Paramecocephala fusca (Haglund, 1868) comb. nov. A key to the species is presented.

Revisão do gênero Paramecocephala Benvegnú, 1968 (Heteroptera, Pentatomidae)

Revision of the genus Paramecocephala Benvegnú, 1968 (Heteroptera, Pentatomidae). The Neotropical genus Paramecocephala Benvegnú, 1968 is revised based on morphological characters, particularly of the genitalia of both sexes. Formerly monobasic with P. foveata Benvegnú, 1968, type species, the genus received two species recently transferred from Mecocephala Dallas, 1851: M. fusca Haglund, 1868 and M. uruguayensis Pirán, 1970. Five new species are herein described: P. australis Frey-da-Silva & Grazia sp. nov., P. bachmanni Frey-da-Silva & Grazia sp. nov., P. bergrothi Frey-da-Silva & Grazia sp. nov., P. guianensis Frey-da-Silva & Grazia sp. nov. and P. subsolana Frey-da-Silva & Grazia sp. nov. Illustrations of the genitalia, a key to the species and a distribution map are provided.

Sistemática, filogenia e distribuição geográfica das espécies sul-americanas de Centris (Paracentris) Cameron, 1903 e de Centris (Penthemisia) Moure, 1950, incluindo uma análise filogenética do "grupo Centris" sensu Ayala, 1998 (Hymenoptera, Apoidea, Centridini)

Systematics, phylogeny and geographical distribution of the South American species of Centris (Paracentris) Cameron, 1903, and Centris (Penthemisia) Moure, 1950, including a phylogenetic analysis of the "Centris group" sensu Ayala, 1998 (Hymenoptera, Apoidea, Centridini). A cladistic analysis with the objective of testing the hypothesis of monophily of Centris (Paracentris) Cameron, 1903, and of studying its phylogenetic relationships with the other subgenera that belong to the Centris group, sensu Ayala, 1998, and the relationships among the species that occur in South America, is presented. Centris (Paracentris) is a group of New World bees of amphitropical distribution, especially diversified in the Andes and in the xeric areas of South and North America. Thirty-one species were included in the analysis, four considered as outgroup, and 49 characters, all from external morphology and genitalia of adult specimens. Parsimony analyses with equal weights for the characters and successive weighting were performed with the programs NONA and PAUP, and analyses of implied weighting with the program PeeWee. The strict consensus among the trees obtained in all the analyses indicates that C. (Paracentris), as previously recognized, is a paraphyletic group. In order to eliminate that condition, the subgenera C. (Acritocentris), C. (Exallocentris) and C. (Xerocentris), all described by SNELLING (1974) are synonymized under C. (Paracentris). The subgenus C. (Penthemisia) Moure, 1950, previously considered a synonym of C. (Paracentris), is reinstated, but in a more restricted sense than originally proposed and with the following species: Centris brethesi Schrottky, 1902; C. buchholzi Herbst, 1918; C. chilensis (Spinola, 1851), C. mixta mixta Friese, 1904, and C. mixta tamarugalis Toro & Chiappa, 1989. Centris mixta, previously recognized as the only South American species of the subgenus C. (Xerocentris), a group supposedly amphitropical, came out as the sister-species of C. buchholzi. The following South American species were recognized under Centris (Paracentris): Centris burgdorfi Friese, 1901; C. caelebs Friese, 1900; C. cordillerana Roig-Alsina, 2000; C. euphenax Cockerell, 1913; C. flavohirta Friese, 1900; C. garleppi (Schrottky, 1913); C. klugii Friese, 1900; C. lyngbyei Jensen-Haarup, 1908; C. mourei Roig-Alsina, 2000; C. neffi Moure, 2000; C. nigerrima (Spinola, 1851); C. toroi sp. nov.; C. tricolor Friese, 1900; C. unifasciata (Schrottky, 1913), and C. vogeli Roig-Alsina, 2000. The relationships among the subgenera of the "Centris group" were: (Xanthemisia (Penthemisia (Centris s. str. - Paracentris))). Centris xanthomelaena Moure & Castro 2001, an endemic species of the Caatinga and previously considered a C. (Paracentris), came out as the sister group of C. (Centris) s. str. A new species of C. (Paracentris) from Chile is described: Centris toroi sp. nov. Lectotypus designations and redescriptions are presented for Centris burgdorfi, C. caelebs, C. lyngbyei, C. tricolor, C. autrani Vachal, 1904 and C. smithii Friese, 1900. New synonyms proposed: C. buchholzi Herbst, 1918 = Centris wilmattae Cockerell, 1926 syn. nov.; C. caelebs Friese, 1900 = Paracentris fulvohirta Cameron, 1903. The female of C. vogeli Roig-Alsina, 2000 and the male of C. xanthomelaena are described.

Record of two species of Orius Wolff (Hemiptera, Anthocoridae) in Brazil

The genus Orius Wolff, 1811 comprises predatory species, with approximately 70 known species. Informations about the genus in Brazil are scarce. Therefore, the aim of this investigation was to identify Orius species present in four localities in the southeastern Brazil. Samples were taken from several plants, and the material screened in laboratory. The genitalia of both sexes were studied and illustrated. Two species were identified, Orius insidiosus (Say, 1832) and Orius thyestes Herring, 1966. O. insidiosus, the most common species, was collected in all of the localities sampled [Lavras (MG), Holambra, Pindorama and Campinas (SP)]. O. thyestes, registered for the first time in Brazil, occurred only in Lavras (MG) and Pindorama (SP). Some morphologic aspects of these two species are also presented.

Ultrastructure of the eggs of two species of Anopheles (Anopheles) Meigen (Diptera, Culicidae)

Egg ultrastructure of two morphologicaly similar species of the Arribalzagia Series, Anopheles (A.) costai Fonseca & Ramos, 1939 and A. (A.) mediopunctatus (Lutz, 1903) are described and illustrated using scanning electron micrographs. Although similar in the adult stage, male genitalia structures and larval and pupal stages, the eggs of these species are distinct. The eggs of A. costai and A. mediopunctatus are compared with that of A. forattinii Wilkerson & Sallum, 1999. Incomplete illustration of egg of A. forattinii is provided for comparison.

Males of Nectarinella Bequaert (Hymenoptera, Vespidae, Polistinae)

The males of both species of the paper wasp genus Nectarinella Bequaert, N. xavantinensis Mateus & Noll and N. championi (Dover), are described, and the genitalia illustrated. These are compared to species in the closely related genera Chartergellus, Leipomeles, Marimbonda, Parachartergus and Pseudopolybia.