Phase transitions and nonlinear phenomena in neuronal network models

Communication and cooperation between billions of neurons underlie the power of the brain. How do complex functions of the brain arise from its cellular constituents? How do groups of neurons self-organize into patterns of activity? These are crucial questions in neuroscience. In order to answer them, it is necessary to have solid theoretical understanding of how single neurons communicate at the microscopic level, and how cooperative activity emerges. In this thesis we aim to understand how complex collective phenomena can arise in a simple model of neuronal networks. We use a model with balanced excitation and inhibition and complex network architecture, and we develop analytical and numerical methods for describing its neuronal dynamics. We study how interaction between neurons generates various collective phenomena, such as spontaneous appearance of network oscillations and seizures, and early warnings of these transitions in neuronal networks. Within our model, we show that phase transitions separate various dynamical regimes, and we investigate the corresponding bifurcations and critical phenomena. It permits us to suggest a qualitative explanation of the Berger effect, and to investigate phenomena such as avalanches, band-pass filter, and stochastic resonance. The role of modular structure in the detection of weak signals is also discussed. Moreover, we find nonlinear excitations that can describe paroxysmal spikes observed in electroencephalograms from epileptic brains. It allows us to propose a method to predict epileptic seizures. Memory and learning are key functions of the brain. There are evidences that these processes result from dynamical changes in the structure of the brain. At the microscopic level, synaptic connections are plastic and are modified according to the dynamics of neurons. Thus, we generalize our cortical model to take into account synaptic plasticity and we show that the repertoire of dynamical regimes becomes richer. In particular, we find mixed-mode oscillations and a chaotic regime in neuronal network dynamics.

A Democratic Opening? The AKP and the Kurdish Left

Since its foundation, militant democratic arguments have underpinned an enforced secularism in Turkey. The 2002 election of the AKP, described as a “moderate Islamist party”, has challenged Turkey’s secular identity. In the more than twelve years since the AKP has been in power, Turkey’s political landscape has experienced significant changes, with periods of extensive democratic reforms punctuated by regression in certain areas, notably freedom of expression and the right to protest. State repressive measures coupled with Recep Tayyip Erdoğan’s reluctance to exit the political stage have been the focus of much commentary and analysis. This article argues, however, that under AKP rule the Kurdish issue – critical to ensuring the normalization of politics and democratization in Turkey – has been brought in from the political cold and assesses the creation and role of the HDP (Halkların Demokratik Partisi), a Kurdish political party that is endeavoring to situate itself in the mainstream of Turkey’s political landscape. We posit that the HDP can be viewed as the offspring of this “democratic opening,” a project that was meant to ensure a radical transformation of the Kurdish issue in Turkey. Through analysing the historical trajectory of both AKP and HDP and the militant democratic arguments that led to their predecessors’ exclusion from the public sphere, this article engages with the key question of the extent to which the AKP’s treatment of the Kurdish issue has provided a vehicle for broader democratisation and facilitated a reconsideration of the Kurdish question in Turkey.

Explaining party cohesion and discipline in democratic legislatures: purposiveness and contexts

Legislative party discipline and cohesion are important phenomena in the study of political systems. Unless assumptions are made that parties are cohesive and act as unified collectivities with reasonably well-defined goals, it is really difficult, if not impossible, to consider their electoral and legislative roles usefully. But levels of legislative party cohesiveness are also important because they provide us with crucial information about how legislatures/ parliaments function and how they interact with executives/governments. Without cohesive (or disciplined) parties,1 government survival in parliamentary systems is threatened because executive and legislative powers are fused while in separated systems presidents' bases of legislative support become less stable. How do we explain varying levels of legislative party cohesion? The first part of this article draws on the purposive literature to explore the benefits and costs to legislators in democratic legislatures of joining and acting collectively and individualistically within political parties. This leads on to a discussion of various conceptual and empirical problems encountered in analysing intra-party cohesion and discipline in democratic legislatures on plenary votes. Finally, the article reviews the extant empirical evidence on how a multiplicity of systemic, party-levels and situational factors supposedly impact cohesion/discipline levels. The article ends with a discussion of the possibilities and limitations of building comparative models of cohesion/discipline.

The Media as a Window on the Past? The Impact of Television and Newspaper Consumption on Knowledge of the Democratic Transition in Portugal

This study seeks to expand our understanding of how the media increase the level of political information, by focusing on an understudied yet important learning outcome: knowledge of the political past. The article explores the factors underlying variation in the recognition of the leading actors in the transitional process in Portugal. The results show that television news and newspaper exposure foster recognition of these actors, but that media use interacts with personal experience of the transition (stronger effects among younger cohorts) and party identification (stronger impact on those who do not feel close to a political party).

The resilience of democratic institutions in Britain, Australia and the United States under conditions of total war

To what extent are democratic institutions resilient when nation states mobilise for war? Normative and empirical political theorists have long argued that wars strengthen the executive and threaten constitutional politics. In modern democracies, national assemblies are supposed to hold the executive to account by demanding explanations for events and policies; and by scrutinising, reviewing and, if necessary, revising legislative proposals intended to be binding on the host society or policies that have been implemented already. This article examines the extent to which the British and Australian parliaments and the United States Congress held their wartime executives to account during World War II. The research finds that under conditions approaching those of total war, these democratic institutions not only continued to exist, but also proved to be resilient in representing public concerns and holding their executives to account, however imperfectly and notwithstanding delegating huge powers. In consequence, executives—more so British and Australian ministers than President Roosevelt—were required to be placatory as institutional and political tensions within national assemblies and between assemblies and executives continued, and assemblies often asserted themselves. In short, even under the most onerous wartime conditions, democratic politics mattered and democratic institutions were resilient.

Parties in democratic national assemblies: comparative assessment of parliaments note

This paper argues that the analysis of democratic national assemblies is not only impossible without discussing political parties, but also incomprehensible without recognizing parties as the most significant organizations within them. Parties have structured political groupings and demands on government even before assemblies were democratically elected. And although parties may be in decline as institutions mediating between society and government in the current era, they remain significant as organizing forces within government. The paper first explains the origins of party organizations within parliaments by exploring why individual members and the assemblies taken as a whole need parties: what are their costs and benefits? It then describes the manner in which party organizations operate in different national assembly chambers. The third section analyses types and sources of party influence, including the role played by party leaders in manipulating legislative agendas, structuring Members’ policy choices and shaping policy outcomes. The final section reviews how politi- cal scientists have sought to explain intra-party cohesion and discipline across different national assemblies.

The Potential of Participedia as a Crowdsourcing Tool for Comparative Analysis of Democratic Innovations

For two reasons, our capacity for systematic comparison of innovative participatory democratic processes remains limited. First, the category of participatory democratic innovations remains relatively vague when compared to more traditional democratic institutions and practices. Second, until recently there existed no large-sample databases that captured relevant variables in the practice of democratic innovation. The lone exception to these patterns is the Participedia database, located online. Participedia is well placed to respond to the two obstacles to systematic comparative research on democratic innovation. First, its crowdsourced data collection strategy means that many of the cases on the platform are not well known and have not been the subject of sustained academic analysis. Second, the data captured in the articles provides the basis for systematic comparative analysis of democratic innovations both within type (e.g., participatory budgeting, mini-publics) and across types. The platform allows for systematic content analysis of text descriptions and/or statistical analysis of the datasets generated from the structured data fields. This article describes the data about innovative participatory democratic processes available from Participedia, and furnishes examples of the kinds of quantitative and qualitative insights about those processes that Participedia enables.

Modulation of a cytoskeletal calpain-like protein induces major transitions in trypanosome morphology

Individual eukaryotic microbes, such as the kinetoplastid parasite Trypanosoma brucei, have a defined size, shape, and form yet transition through life cycle stages, each having a distinct morphology. In questioning the structural processes involved in these transitions, we have identified a large calpain-like protein that contains numerous GM6 repeats (ClpGM6) involved in determining T. brucei cell shape, size, and form. ClpGM6 is a cytoskeletal protein located within the flagellum along the flagellar attachment zone (FAZ). Depletion of ClpGM6 in trypomastigote forms produces cells with long free flagella and a shorter FAZ, accompanied by repositioning of the basal body, the kinetoplast, Golgi, and flagellar pocket, reflecting an epimastigote-like morphology. Hence, major changes in microbial cell form can be achieved by simple modulation of one or a few proteins via coordinated association and positioning of membrane and cytoskeletal components.

Transitions In Regional Science – Regions In Transitions: Regional Research In Central Europe

There are no exact boundaries of what constitutes Central Europe, but it is nevertheless very evident as a zone of interloping forces stretching across Europe. The result has been negotiated, conflictual and contested processes defining an essentially virtual, discursive, yet also actually existing, space of ‘Central Europe’. Yet, and this is the particular message of this collection of essays, ‘transition’ has not merely been a process ‘on the ground’ as object of investigation and discussion, but has also affected the observers, especially academic commentators and analysts – both within Central Europe, but also outside. This includes a growing interaction between discussions and analyses ‘inside’ and ‘outside’ Central Europe on the phenomenon of ‘transition’. The result has been mutual learning processes and changes of ways of looking at things and interpreting them. The book is divided into two parts, roughly reflecting the two key research questions.The first part (A) is devoted to transitions in regional science. Part B focuses on changes in variety of territorial structures and developmentissues caused by Central-European transitions and which are resulting in differential pathways of regional development in the region.

The Impact of income support programs on transitions to employment

The income support programs are created with the purpose of fighting both, the poverty trap and the inactivity trap. The balance between both is fragile and hard to find. Thus, the goal of this work is to contribute to solve this issue by finding how income support programs, particularly the Portuguese RSI, affect transitions to employment. This is made through duration analysis, namely using Cox and Competing Risks models. A particular feature is introduced in this work as it incorporates the possibility of Defective Risks. The estimated hazard elasticity with respect to the amount of RSI received for individuals who move to employment is -0,41. More than a half of RSI receivers stays for more than a year and the probability of never leaving to employment is 44%. The results appear to indicate that RSI has affected negatively transitions to employment.

The waning of the two giants: the electoral decline of the Italian Christian Democratic Party and the Italian Communist Party

Italy is currently experiencing profound political change. One aspect of this change involves the decline in electoral support for the Italian Christian Democratic Party (DC) and the Italian Communist Party (PCI), now the Democratic Party of the Left (PDS). Signs of the electoral decline of both parties began to appear in the late 1970s and early 1980s and accelerated in the late 1980s and early 1990s. The pr imar y purpos e of th is thes is is to expla i n the electoral decline of the DC and PCI/PDS in the last decade. The central question being addressed in this thesis is the following: What factors contributed to the decline in electoral support for the DC and PCI? In addition, the thesis attempts to better comprehend the change in magni tude and direction of the Italian party system. The thesis examines the central question within an analytical framework that consists of models explaining electoral change in advanced industrial democracies and in Italy. A review of the literature on electoral change in Italy reveals three basic models: structural (socioeconomic and demographic factors), subcultural (the decline of the Catholic and Communist subcultures), and pol i tical (factors such as party strategy, and the crisis and collapse of communism in iv Eastern Europe and the former soviet Union and the end to the Cold War). Significant structural changes have occurred in Italy, but they do not invariably hurt or benefit either party. The Catholic and Communist subcultures have declined in size and strength, but only gradually. More importantly, the study discovers that the decline of communism and party strategy adversely affected the electoral performances of the DC and PC!. The basic conclusion is that political factors primarily and directly contributed to the decline in electoral support for both parties, while societal factors (structural and subcultural changes) played a secondary and indirect role. While societal factors do not contribute directly to the decline in electoral support for both parties, they do provide the context within which both parties operated. In addition, the Italian party system is becoming more fragmented and traditional political parties are losing electoral support to new political movements, such as the Lega Nord (LN-Northern League) and the Rete (Network). The growing importance of the North-South and centre-periphery cleavages suggests that the Italian party system, which is traditionally based on religious and ideological cleavages, may be changing.