The study of neurons is of fundamental importance in biology and medicine. Neurons are the most basic unit of information processing in the nervous system of humans and all other vertebrates and in complex invertebrates. In addition, networks of neurons (the human brain) are the most sophisticated computational devices known, and the study of neurons individually and working in concert is seen as a step toward understanding consciousness and cognition. In the 1950's Hodgkin and Huxley developed a system of nonlinear ordinary differential equations to describe the behavior of a neuron found in the squid. Equations of this form have since been used to model the behavior of a multitude of neurons across a broad spectrum of species. Hodgkin-Huxley type neuron models helped lay the foundation for computational neuroscience, and they remain widely used in the study of neuron behavior almost sixty years after their development. Hodgkin-Huxley type models accept a set of parameters as input and generate data describing the electrical activity of the neuron as a function of time. We develop inversion algorithms to predict a set of input parameter values from the voltage trace data generated by the model. We test our algorithm on data from the Hodgkin-Huxley equations, and we extend the algorithm to solve the inverse problem associated with a more complex Hodgkin-Huxley type model for a lobster stomatogastric neuron. We find strong empirical evidence that the algorithms produce parameter values that generate a good fit to the target voltage trace, and we prove that under certain conditions the inversion algorithm for the Hodgkin-Huxley equations converges to a perfect match. To our knowledge this is the first parameter optimization procedure for which convergence has been shown theoretically. Understanding the relationship between the parameters of a neuron model and its output has implications for designing effective neuron models and for explaining the mechanisms by which neurons regulate their behavior. Inversion algorithms for Hodgkin-Huxley type neuron models are an important theoretical and practical step toward understanding the relationship between model parameters and model behavior, and toward the larger problem of inferring neuronal parameters from behavior observed experimentally.

No description available.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

Thesis (M. Phil.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 144-147).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1975. / Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Esta dissertação propõe uma leitura do romance Admirável Mundo Novo (1932) de Aldous Huxley sob a luz dos conceitos de Zygmunt Bauman da Modernidade Líquida. A narrativa ocorre em uma Londres futurística no século 26, no ano 2540 de nossa Era Comum, ou – na narrativa no ano 632 AF (Após Ford). Subjacente ao cenário distópico de avanço tecnológico e organização altamente desenvolvida, porém, os temas discutidos no romance remetem à circunstância do tempo e lugar de sua produção, o início dos anos 1930, em um contexto de desenvolvimento industrial, tensão política e crise econômica. Nesta pesquisa, eu busco a resposta para a seguinte pergunta: “De quais maneiras a ficção de Huxley antecipa o tipo de sociedade seus leitores vivem no tempo presente, três-quartos de século após sua publicação? Com ajuda das teorias do Professor Zygmunt Bauman, eu construo minha interpretação das metáforas encontradas no romance, que prognosticam as atuais condições de capitalismo de mercado livre, consumismo, obsolescência programada que determinam a ética, a estética e a forma de pensar de nosso tempo presente. As hipóteses de Bauman concernem a liquidez do mundo atual, no qual nada deve durar muito. Esta premissa gera um grande número de consequências, tais como: fragilidade dos laços humanos, pensamento crítico superficial e supremacia dos contatos virtuais sobre ocontato de fato entre as pessoas. A dissertação está dividida em quatro capítulos. No primeiro, eu contextualizo o conceito de distopia. No segundo, eu trago a contextualização necessária sobre o tempo, a obra e o autor. No terceiro, eu introduzo os conceitos de Bauman sobre modernidade sólida e líquida e os conecto com o estudo de Admirável Mundo Novo. No capítulo IV, apresento minha leitura da obra. Ao final da pesquisa, espero encontrar respostas para a questão proposta estabelecendo inter-relações entre os aspectos ficcionais do romance e os traços sociais de nosso tempo atual. / The present thesis proposes a reading of Aldous Huxley’s Brave New World (1932) in the light of Zygmunt Bauman’s concept of Liquid Modernity. The plot of the novel unfolds in the futuristic London of the 26th century, in the year 2540 of our Common Era, or – in the narrative – in the year 632 AF (After Ford). Underlying the dystopian scenario of technological advancement and highly developed organization, however, the themes discussed in the novel actually address the circumstances of the time and place of its own production, the beginning of the 1930’s, in a context of developing industrialization, political tension, and economic crises. In this research, I pursue the answer to the following question: “In what ways does Huxley’s fiction anticipate the kind of society its readers would be living in at our present time, three quarters of a century after its publication?” With the help of Professor Zygmunt Bauman’s theories, I build my interpretation of the metaphors found in the novel, that prognosticate the current conditions of free-market capitalism, consumerism, programmed obsolescence, that determine the ethics, the aesthetics and the ways of thinking of our present times. Bauman’s assumptions concern the liquidity of the contemporary world, where nothing is meant to last long. This premise generates a number of consequences such as overconsumption, frail human bonds, superficial critical thought, and supremacy of online over factual contacts among people. The thesis is devised in three chapters. In the first, I contextualize the concept of dystopia. In the second, I bring the necessary contextualization about the time, the work and the author. In the third, I introduce Bauman’s concepts of solid modernity and liquid modernity and connect them with the study of Brave New World. Finally. In Chapter IV, I present my reading of the novel. At the end of the research, I expect to find the answers to the posed question by establishing critical interrelations between the fictional aspects of the novel and the social features ongoing in our present time.

Aldous Huxley´s Brave New World describes how a totalitarian power has taken control over both body and mind of the whole population. A hierarchical caste system, where a person´s role in society is predetermined long before birth, maintains stability together with brain-washing methods and propaganda. Huxley expressed his fears of what might happen if science was used for the wrong purposes, and wrote his futuristic novel Brave New World in the beginning of the 1930s, inspired by the turbulent world around him. It was a time preoccupied with race and classification of populations, which ended in the disastrous Holocaust. Huxley´s novel is equally important today when eugenics is on the comeback and democracy is challenged by nationalist and populist movements. This essay will consist of a close reading of Brave New World, analyzed from the perspective of the theories of French philosopher Foucault. He launched his concept of biopower in the 1970s, where he linked a negative use of controlling citizens with state racism. The focus of this essay will be to explore how biopower and racism are used by the totalitarian state in the novel to maintain control of the population. The argument will be made that racism, internal division and exclusion are vital tools to achieve that purpose.

Resumo: O objetivo do presente trabalho é desenvolver uma análise comparativa entre as obras Admirável mundo novo e A ilha, de autoria do autor britânico Aldous Leonard Huxley e inscritas na chamada literatura utópica / distópica. Após discorrer sobre a perenidade e a relevância do utopismo enquanto expressão substancialmente crítica do pensamento humano ao longo dos séculos, focalizamos a representatividade das projeções utópicas como signos da modernidade e mecanismos de problematização da realidade experimental nos séculos XIX e XX. Nesse contexto, defendemos a influência da sensibilidade romântica nas figurações ficcionais de Huxley, aspecto que o caracteriza como um autor vinculado à corrente ideológica denominada por Lukács de romantismo anticapitalista. Ao longo da análise, demonstramos que elementos problemáticos das projeções utópicas - o apagamento das individualidades e a consequente normalização das identidades, a alienação e o impulso materialista - são utilizados por Huxley como instrumentos de crítica à expansão do racionalismo capitalista. Comprovamos no decorrer da argumentação que tal processo de contestação se efetiva tanto pela radicalização distópica em Admirável mundo novo, quanto pela destruição do idílio utópico em A ilha. A complementariedade das duas perspectivas, portanto, fornece subsídios para apontar a dicção literária de Aldous Huxley como uma das mais críticas de seu tempo.

Esta dissertação propõe uma leitura do romance Admirável Mundo Novo (1932) de Aldous Huxley sob a luz dos conceitos de Zygmunt Bauman da Modernidade Líquida. A narrativa ocorre em uma Londres futurística no século 26, no ano 2540 de nossa Era Comum, ou – na narrativa no ano 632 AF (Após Ford). Subjacente ao cenário distópico de avanço tecnológico e organização altamente desenvolvida, porém, os temas discutidos no romance remetem à circunstância do tempo e lugar de sua produção, o início dos anos 1930, em um contexto de desenvolvimento industrial, tensão política e crise econômica. Nesta pesquisa, eu busco a resposta para a seguinte pergunta: “De quais maneiras a ficção de Huxley antecipa o tipo de sociedade seus leitores vivem no tempo presente, três-quartos de século após sua publicação? Com ajuda das teorias do Professor Zygmunt Bauman, eu construo minha interpretação das metáforas encontradas no romance, que prognosticam as atuais condições de capitalismo de mercado livre, consumismo, obsolescência programada que determinam a ética, a estética e a forma de pensar de nosso tempo presente. As hipóteses de Bauman concernem a liquidez do mundo atual, no qual nada deve durar muito. Esta premissa gera um grande número de consequências, tais como: fragilidade dos laços humanos, pensamento crítico superficial e supremacia dos contatos virtuais sobre ocontato de fato entre as pessoas. A dissertação está dividida em quatro capítulos. No primeiro, eu contextualizo o conceito de distopia. No segundo, eu trago a contextualização necessária sobre o tempo, a obra e o autor. No terceiro, eu introduzo os conceitos de Bauman sobre modernidade sólida e líquida e os conecto com o estudo de Admirável Mundo Novo. No capítulo IV, apresento minha leitura da obra. Ao final da pesquisa, espero encontrar respostas para a questão proposta estabelecendo inter-relações entre os aspectos ficcionais do romance e os traços sociais de nosso tempo atual. / The present thesis proposes a reading of Aldous Huxley’s Brave New World (1932) in the light of Zygmunt Bauman’s concept of Liquid Modernity. The plot of the novel unfolds in the futuristic London of the 26th century, in the year 2540 of our Common Era, or – in the narrative – in the year 632 AF (After Ford). Underlying the dystopian scenario of technological advancement and highly developed organization, however, the themes discussed in the novel actually address the circumstances of the time and place of its own production, the beginning of the 1930’s, in a context of developing industrialization, political tension, and economic crises. In this research, I pursue the answer to the following question: “In what ways does Huxley’s fiction anticipate the kind of society its readers would be living in at our present time, three quarters of a century after its publication?” With the help of Professor Zygmunt Bauman’s theories, I build my interpretation of the metaphors found in the novel, that prognosticate the current conditions of free-market capitalism, consumerism, programmed obsolescence, that determine the ethics, the aesthetics and the ways of thinking of our present times. Bauman’s assumptions concern the liquidity of the contemporary world, where nothing is meant to last long. This premise generates a number of consequences such as overconsumption, frail human bonds, superficial critical thought, and supremacy of online over factual contacts among people. The thesis is devised in three chapters. In the first, I contextualize the concept of dystopia. In the second, I bring the necessary contextualization about the time, the work and the author. In the third, I introduce Bauman’s concepts of solid modernity and liquid modernity and connect them with the study of Brave New World. Finally. In Chapter IV, I present my reading of the novel. At the end of the research, I expect to find the answers to the posed question by establishing critical interrelations between the fictional aspects of the novel and the social features ongoing in our present time.

Abstract Visual world is naturally correlated both spatially and temporally. The correlations are used in vision to enhance performance of neurons. For gaining maximal neural performance of the visual neurons, the experiments, from stimulus to the analysis, should be designed to take advantage of the correlations. In this thesis methods for generating and analyzing natural stimuli were examined by using computations and algorithms. For analyzing responses to natural stimuli in visual neurons, a method with only a few assumptions was developed for estimating information rate in long responses. The novel method gave a good agreement with Shannon information rate with linear system and Gaussian input but was able to handle also nonlinear processing and non-Gaussian data. Secondly, a computer controlled 3D virtual environment with a spherical screen was developed, with a large visual field. The image of the world was projected to the screen with a DLP projector, giving good enough temporal performance for insect vision research. A track-ball was used in closed loop experiments. Thirdly, properties of single photon (“bump”) information transfer at various light levels were investigated in cockroach photoreceptor with a coarse computational model. At dim light (< 10 ph/s), where single bump responses were visible, shot noise was dominant. At higher light levels latency distribution of the bump decreased the information rate, but amplitude distribution of bump did not have an effect. Fourthly, the contribution of K⁺ channels to information rate and energy consumption was investigated by creating a database of computation models with varying channel compositions. The information rate has a maximum as a function of mean conductance, which was a sum of the average K⁺ conductance and the leak conductance. This maximum was fine-tuned by the K⁺ channel composition, which had high so-called novel contribution and relatively low amount of other conductances.