Polygenic dynamics underlying the response of quantitative traits to directional selection

We study the response of a quantitative trait to exponential directional selection in a finite haploid population at the genetic and the phenotypic level. We assume an infinite sites model, in which the number of new mutations per generation in the population follows a Poisson distribution (with mean $\Theta$) and each mutation occurs at a new, previously monomorphic site. Mutation effects are beneficial and drawn from a distribution. Sites are unlinked and contribute additively to the trait. Assuming that selection is stronger than random genetic drift, we model the initial phase of the dynamics by a supercritical Galton-Watson process. This enables us to obtain time-dependent results. We show that the copy-number distribution of the mutant in generation n, conditioned on non-extinction until n, is described accurately by the deterministic increase from an initial distribution with mean 1. This distribution is related to the absolutely continuous part $W^+$ of the random variable, typically denoted $W$, that characterizes the stochasticity accumulating during the mutant's sweep. On this basis, we derive explicitly the (approximate) time dependence of the mutant frequency distribution, of the expected mean and variance of the trait and of the expected number of segregating sites. Unexpectedly, we obtain highly accurate approximations for all times, even for the quasi-stationary phase where we refine classical results. In addition, we find that $\Theta$ is the main determinant of the pattern of adaptation at the genetic level, i.e., whether the initial allele-frequency dynamics are best described by sweep-like patterns at few loci or small allele-frequency shifts at many. The selection strength determines primarily the rate of adaptation. The accuracy of our results is tested by comprehensive simulations in a Wright-Fisher framework

Digital divides in the social construction of history: Editor representation in Wikipedia articles on African independence processes

Ziel des vorliegenden Beitrages ist es, verschiedene Formen digitaler Ungleichheit im Rahmen von Kollaborationsprozessen online zu untersuchen. Konkret analysieren wir digitale Ungleichheiten hinsichtlich der geografischen Herkunft von Editor*innen der Wikipedia. Der aktuelle Forschungsstand zeigt, dass Teilnehmer*innen aus Industrieländern hier besonders stark vertreten sind, während in anderen Regionen (insbesondere in sogenannten Entwicklungsländern) kaum Menschen teilnehmen. Die vorliegende Studie untersucht, wie sich die Autor*innengeographie in der Bearbeitung (Partizipation, Einfluss und Erfolg) von Artikeln zu den Unabhängigkeitsprozessen ehemaliger Kolonien in Afrika widerspiegelt. Die Analyse basiert auf insgesamt 354 Wikipedia-Artikeln. Anhand der Geolokalisierung von 75% der beteiligten Editor*innen (N = 23.408) zeigen wir, dass die meisten Bearbeitungen von Editor*innen aus Frankreich vorgenommen werden. Dieses Ungleichgewicht zeigt sich auch gemessen am gesamten Textanteil im Laufe der Zeit. Auf der Ebene der einzelnen Nutzer*innen lässt sich jedoch feststellen, dass Editor*innen aus Frankreich nur geringfügig erfolgreicher sind als jene aus den afrikanischen Nachfolgestaaten, wenn es um die längerfristige Sichtbarkeit ihrer Beiträge geht.The aim of the present paper is to examine different forms of digital divides that may occur during online collaboration. Specifically, we analyse digital inequalities regarding the geographical origin of editors active on Wikipedia. Existing evidence suggests a strong geographic bias among Wikipedia editors, as industrialized countries are strongly represented while others (especially developing countries) are virtually absent. The present study examines how editor geography is reflected in the editing of articles (participation, impact and success) about the independence of former French colonies in Africa. The analysis is based on 354 Wikipedia articles; by geolocating 75% of the editors (N = 23,408), we show that the majority of edits are made by users located in France. This imbalance is also reflected in the overall share of text they contribute over time. However, when looking at the individual user level, we find that editors from France are only slightly more successful in maintaining their contributions visible to the reader, than editors from African successor states

The multilingual Twitter-discourse on vaccination in Germany during the COVID-19 pandemic

There is evidence that specific segments of the population were hit particularly hard by the Covid-19 pandemic (e.g., people with a migration background). In this context, the impact and role played by online platforms in facilitating the integration or fragmentation of public debates and social groups is a recurring topic of discussion. This is where our study ties in, we ask: How is the topic of vaccination discussed and evaluated in different language communities in Germany on Twitter during the Covid-19 pandemic? We collected all tweets in German, Russian, Turkish, and Polish (i.e., the largest migrant groups in Germany) in March 2021 that included the most important keywords related to Covid-19 vaccination. All users were automatically geocoded. The data was limited to tweets from Germany. Our results show that the multilingual debate on Covid-19 vaccination in Germany does not have many structural connections. However, in terms of actors, arguments, and positions towards Covid-19 vaccination, the discussion in the different language communities is similar. This indicates that there is a parallelism of the debates but no social-discursive integration

Poetics/Poelitics of materiality in latin american digital poetry

Este artículo propone leer la poesía digital latinoamericana en vinculación con el acontecimiento poético-político que emerge cuando se considera su materialidad. Dar visibilidad a la materialidad habilita limitar la naturalización de los sentidos que vienen asociados a la cultura digital hegemónica contemporánea. Esto se logra desde procedimientos que ponen de relieve tanto los diversos niveles de materialidad inherentes a cada evento artístico literario digital —materialidad textual de superficie, materialidad relacional de las interfaces tanto de software como de hardware, materialidad del código— como los modos convencionales de ser con y hacer sentido de los entramados técnicos digitales que organizan nuestra vida cotidiana.This paper aims to read Latin American digital poetry in regards to the poetic-political event that emerges whenever its materiality is considered. To make materiality visible enables one to restrict the naturalization of meanings associate with contemporary hegemonic digital culture. This is accomplished through artistic procedures that emphasize, on the one hand, the multiple levels of materiality inherent to digital literary works— surface/textual materiality, software and hardware interface relational materiality, code materiality—and, on the other hand, the conventional ways to interact with and build meaning within the digital space that organize everyday life.Fil: Kozak, Claudia. Universidad de Buenos Aires. Facultad de Ciencias Sociales. Instituto de Investigaciones "Gino Germani". Estudios Culturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Tres de Febrero; Argentin

The genetic architecture of the human cerebral cortex

The cerebral cortex underlies our complex cognitive capabilities, yet little is known about the specific genetic loci that influence human cortical structure. To identify genetic variants that affect cortical structure, we conducted a genome-wide association meta-analysis of brain magnetic resonance imaging data from 51,665 individuals. We analyzed the surface area and average thickness of the whole cortex and 34 regions with known functional specializations. We identified 199 significant loci and found significant enrichment for loci influencing total surface area within regulatory elements that are active during prenatal cortical development, supporting the radial unit hypothesis. Loci that affect regional surface area cluster near genes in Wnt signaling pathways, which influence progenitor expansion and areal identity. Variation in cortical structure is genetically correlated with cognitive function, Parkinson's disease, insomnia, depression, neuroticism, and attention deficit hyperactivity disorder

The role of frontal midline theta oscillation in cognitive control

Die θ-Band- und die θ-γ-Frequenzkopplung (CFC) des cingulären und des frontalen Kortex wurden bereits mit grundlegenden Prozessen der kognitiven Kontrolle in Verbindung gebracht. In dieser Arbeit wird daher die Rolle spezifischer Oszillationen des Gehirns in Bezug auf kognitive Kontrolle mit Hilfe von nichtinvasiver Hirnstimulation untersucht. Wir verwendeten ein randomisiertes, doppelblindes Studiendesign, bei dem gesunde Teilnehmer*innen einer transkraniellen Wechselstromstimulation (tACS) ausgesetzt wurden. In drei verschiedenen Studienaufbauten untersuchten wir die Auswirkungen der tACS mittels θ-Band- und θ-γ-CFC-Stimulation. Die Hirnstimulation wurde während einer Go/NoGo-Aufgabe mit monetärer Belohnung und Bestrafung zur Überprüfung des instrumentellen Lernens durchgeführt. Unsere Ergebnisse legen nahe, dass die kognitive Kontrolle von der Dauer und der Frequenz der Stimulation abhängt. Außerdem deuten die Ergebnisse darauf hin, dass die Auswirkungen der Stimulation während des CFC-Protokolls phasenspezifisch sind.θ band and θ-γ cross-frequency coupling (CFC) of the cingulate and frontal cortices have been linked to fundamental processes of cognitive control. This work investigates the role of specific brain oscillations in cognitive control by using noninvasive brain stimulation. We used a double-blind, randomized study design were healthy participants were subjected to transcranial alternating current stimulation (tACS). In three different study designs we evaluated the effects of tACS using θ band and θ-γ CFC stimulation. The brain stimulation was applied during a Go/NoGo monetary reward- and punishment-based instrumental learning task. Our results suggest that cognitive control depends on the length and the frequency of the stimulation. Furthermore, the findings indicate that effects of the stimulation are phase specific during the CFC protocol

Conflict dynamics in collaborative knowledge production. A study of network gatekeeping on Wikipedia (supplementary material).

This project provides supplementary information for the study "Conflict dynamics in collaborative knowledge production. A study of network gatekeeping on Wikipedia". It encompasses a complementary documentation of our methodological approach, a list of the Wikipedia-articles included in the sample, and the risk sets on which the Relational Event Models are based

Ө-γ Cross-Frequency Transcranial Alternating Current Stimulation over the Trough Impairs Cognitive Control

Cognitive control is a mental process, which underlies adaptive goal-directed decisions. Previous studies have linked cognitive control to electrophysiological fluctuations in the θ band and θ-γ cross-frequency coupling (CFC) arising from the cingulate and frontal cortices. However, to date, the behavioral consequences of different forms of θ-γ CFC remain elusive. Here, we studied the behavioral effects of the θ-γ CFC via transcranial alternating current stimulation (tACS) designed to stimulate the frontal and cingulate cortices in humans. Using a double-blind, randomized, repeated measures study design, 24 healthy participants were subjected to three active and one control CFC-tACS conditions. In the active conditions, 80-Hz γ tACS was coupled to 4-Hz θ tACS. Specifically, in two of the active conditions, short γ bursts were coupled to the delivered θ cycle to coincide with either its peaks or troughs. In the third active condition, the phase of a θ cycle modulated the amplitude of the γ oscillation. In the fourth, control protocol, 80-Hz tACS was continuously superimposed over the 4-Hz tACS, therefore lacking any phase specificity in the CFC. During the 20 min of stimulation, the participants performed a Go/NoGo monetary reward-based and punishment-based instrumental learning task. A Bayesian hierarchical logistic regression analysis revealed that relative to the control, the peak-coupled tACS had no effects on the behavioral performance, whereas the trough-coupled tACS and, to a lesser extent, amplitude-modulated tACS reduced performance in conflicting trials. Our results suggest that cognitive control depends on the phase specificity of the θ-γ CFC