Inferring processes of cultural transmission: the critical role of rare variants in distinguishing neutrality from novelty biases

Neutral evolution assumes that there are no selective forces distinguishing different variants in a population. Despite this striking assumption, many recent studies have sought to assess whether neutrality can provide a good description of different episodes of cultural change. One approach has been to test whether neutral predictions are consistent with observed progeny distributions, recording the number of variants that have produced a given number of new instances within a specified time interval: a classic example is the distribution of baby names. Using an overlapping generations model we show that these distributions consist of two phases: a power law phase with a constant exponent of -3/2, followed by an exponential cut-off for variants with very large numbers of progeny. Maximum likelihood estimations of the model parameters provide a direct way to establish whether observed empirical patterns are consistent with neutral evolution. We apply our approach to a complete data set of baby names from Australia. Crucially we show that analyses based on only the most popular variants, as is often the case in studies of cultural evolution, can provide misleading evidence for underlying transmission hypotheses. While neutrality provides a plausible description of progeny distributions of abundant variants, rare variants deviate from neutrality. Further, we develop a simulation framework that allows for the detection of alternative cultural transmission processes. We show that anti-novelty bias is able to replicate the complete progeny distribution of the Australian data set

NMDAR-Mediated Calcium Transients Elicited by Glutamate Co-Release at Developing Inhibitory Synapses

Before hearing onset, the topographic organization of the inhibitory sound localization pathway from the medial nucleus of the trapezoid body (MNTB) to the lateral superior olive (LSO) is refined by means of synaptic silencing and strengthening. During this refinement period MNTB-LSO synapses not only release GABA and glycine but also release glutamate. This co-released glutamate can elicit postsynaptic currents that are predominantly mediated by NMDA receptors (NMDARs). To gain a better understanding of how glutamate contributes to synaptic signaling at developing MNTB-LSO inhibitory synapses, we investigated to what degree and under what conditions NMDARs contribute to postsynaptic calcium responses. Our results demonstrate that MNTB-LSO synapses can elicit compartmentalized calcium responses along aspiny LSO dendrites. These responses are significantly attenuated by the NMDAR antagonist APV. APV, however, had no effect on somatically recorded electrical postsynaptic responses, indicating little, if any, contribution of NMDARs to spike generation. NMDAR-mediated calcium responses were decreased when increasing extracellular magnesium concentrations to physiological levels indicating that MNTB-LSO synapses activate magnesium sensitive NMDAR on immature LSO dendrites. In Fura-2 AM loaded neurons, blocking GABAA and glycine receptors increased NMDAR contribution to somatic calcium responses suggesting that GABA and glycine, perhaps by shunting backpropagating action potentials, decrease the level of NMDAR activation under strong stimulus conditions

Positive electrodes of nickel-cadmium batteries

Ni hydroxide sintered electrodes which are filled electrochemically are superior to chemically treated electrodes. In the electrochemical process, the hydroxide grows on the Ni grains and possesses a well-defined porous structure. Diffusion and conducting mechanisms are therefore facilitated

Power and the Medium Munich as a Paradigm for an Analysis of Current Power Structures?

The question is, how far in the context of printing there may still happen presence-phenomena taking back the human body? Bavarian printing seems to make it possible, to give an answer. Therefore theoretical explanations on the value of re-updating and re-personalising as the basic techniques as well as re-presence as the basic intention of media-communicated political behaviour aiming at power or its retention are important. The given model itself is fruitful for processes and shifts of current politics. The 16thand the 21st century may be reasonably compared to each other, as both then and now radical changes of the media (human body or physical communication and printing on the one hand, printing and the new media on the other hand) can be observed as the communications-theoretical signature of the time. The claim of media then and now is to generate re-presence of the human body, which has consequences on the power and its production

Demography and Language Competition

Attempts to describe language competition and extinction in a mathematical way have enjoyed increased popularity recently. In this paper I review recent modeling approaches and, based on these findings, propose a model of reaction-diffusion type. I analyze the dynamics of interactions of a population with two monolingual groups and a group that is bilingual in these two languages. The results show that demographic factors, such as population growth or population dispersal, play an important role in the competition dynamic. Furthermore, I consider the impact of two strategies for language maintenance: adjusting the status of the endangered language and adjusting the availability of monolingual and bilingual educational resources

Evolving Environmentalism: Contentious Partnerships and Transformational Relationships Between the Environmental Justice Movement and the Mainstream Environmental Movement

Senior Project submitted to The Division of Social Studies of Bard College

Benign familial neonatal convulsions: abnormal intrauterine movements, provocation by feeding and ICTAL EEG

An infant with benign familial neonatal convulsions had abnormal movements during the last 2 months of pregnancy suggestive of intrauterine seizures. His postnatal seizures, one of which was captured by electroencephalography, had both partial and generalized features. Most seizures appeared to be provoked by feeding

Inference of Cultural Transmission Modes Based on Incomplete Information

In this paper we explore the theoretical limits of the inference of cultural transmission modes based on sparse population-level data. We approach this problem by investigating whether different transmission modes produce different temporal dynamics of cultural change. In particular we explore whether the distributions of the average time a variant stays the most common variant in the population, denoted by tmax, conditioned on the considered transmission modes are sufficiently different to allow for inference of underlying transmission modes. We assume time series data detailing the frequencies of different variants of a cultural trait in a population at different points in time and investigate the temporal resolution (i.e. the length of the time series and the distance between consecutive time points) that is needed to ensure distinguishability between transmission modes. We find that under complete information most transmission modes can be distinguished on the base of the statistic tmax, however we should not expect the same results if only infrequent information about the most common cultural variant in the population are available