Transformation of context-dependent sensory dynamics into motor behavior

Latorre R, Levi R, Varona P (2013) Transformation of Context-dependent Sensory Dynamics into Motor Behavior. PLoS Comput Biol 9(2): e1002908. doi:10.1371/journal.pcbi.1002908The intrinsic dynamics of sensory networks play an important role in the sensory-motor transformation. In this paper we use conductance based models and electrophysiological recordings to address the study of the dual role of a sensory network to organize two behavioral context-dependent motor programs in the mollusk Clione limacina. We show that: (i) a winner take-all dynamics in the gravimetric sensory network model drives the typical repetitive rhythm in the wing central pattern generator (CPG) during routine swimming; (ii) the winnerless competition dynamics of the same sensory network organizes the irregular pattern observed in the wing CPG during hunting behavior. Our model also shows that although the timing of the activity is irregular, the sequence of the switching among the sensory cells is preserved whenever the same set of neurons are activated in a given time window. These activation phase locks in the sensory signals are transformed into specific events in the motor activity. The activation phase locks can play an important role in motor coordination driven by the intrinsic dynamics of a multifunctional sensory organThis work was supported by MINECO TIN2012-30883 and IPT-2011-0727-020000

Probing the dynamics of identified neurons with a data-driven modeling approach

In controlling animal behavior the nervous system has to perform within the operational limits set by the requirements of each specific behavior. The implications for the corresponding range of suitable network, single neuron, and ion channel properties have remained elusive. In this article we approach the question of how well-constrained properties of neuronal systems may be on the neuronal level. We used large data sets of the activity of isolated invertebrate identified cells and built an accurate conductance-based model for this cell type using customized automated parameter estimation techniques. By direct inspection of the data we found that the variability of the neurons is larger when they are isolated from the circuit than when in the intact system. Furthermore, the responses of the neurons to perturbations appear to be more consistent than their autonomous behavior under stationary conditions. In the developed model, the constraints on different parameters that enforce appropriate model dynamics vary widely from some very tightly controlled parameters to others that are almost arbitrary. The model also allows predictions for the effect of blocking selected ionic currents and to prove that the origin of irregular dynamics in the neuron model is proper chaoticity and that this chaoticity is typical in an appropriate sense. Our results indicate that data driven models are useful tools for the in-depth analysis of neuronal dynamics. The better consistency of responses to perturbations, in the real neurons as well as in the model, suggests a paradigm shift away from measuring autonomous dynamics alone towards protocols of controlled perturbations. Our predictions for the impact of channel blockers on the neuronal dynamics and the proof of chaoticity underscore the wide scope of our approach

Models wagging the dog: are circuits constructed with disparate parameters?

In a recent article, Prinz, Bucher, and Marder (2004) addressed the fundamental question of whether neural systems are built with a fixed blueprint of tightly controlled parameters or in a way in which properties can vary largely from one individual to another, using a database modeling approach. Here, we examine the main conclusion that neural circuits indeed are built with largely varying parameters in the light of our own experimental and modeling observations. We critically discuss the experimental and theoretical evidence, including the general adequacy of database approaches for questions of this kind, and come to the conclusion that the last word for this fundamental question has not yet been spoken

Sensory dynamics transformation into effective motor behavior

Abstracts from Twenty Second Annual Computational Neuroscience Meeting: CNS*2013 Paris, France. 13-18 July 2013This work was supported by MINECO TIN2012-30883 and IPT-2011-0727-020000

Quality standards for the self-learning of languages through the Internet

[DE] There is a very large supply of online resources for the self-learning of languages available at present on the Web. This abundance is due to a series of demands in society nowadays, such as the need for mobility, life-long learning and, therefore, self-learning. At the same time, there is a great interest in the proposal of universally accepted standards and norms that ensure product quality. In this paper the latter issue is discussed in order to check whether the existing collections of standards and norms include or may be applied to Web-based resources for the self-learning of languages.S207211178

Cosmological singularities in f(T,ϕ)f(T,\phi) gravity

The pursuit of understanding the mysteries surrounding dark energy has sparked significant interest within the field of cosmology. While conventional approaches, such as the cosmological constant, have been extensively explored, alternative theories incorporating scalar field-based models and modified gravity have emerged as intriguing avenues. Among these, teleparallel theories of gravity, specifically the $f(T,\phi)$ formulation, have gained prominence as a means to comprehend dark energy within the framework of teleparallelism. In this study, we investigate two well-studied models of teleparallel dark energy and examine the presence of cosmological singularities within these scenarios. Using the Goriely-Hyde procedure, we examine the dynamical systems governing the cosmological equations of these models. Our analysis reveals that both models exhibit Type IV singularities, but only for a limited range of initial conditions. These results could indicate a potential edge for teleparallel cosmological models over their other modified gravity counterparts, as the models we examine seem to be only allowing for weak singularities that too under non general conditions.Comment: Accepted for publication in EPJC, 29 pages with no figures. arXiv admin note: text overlap with arXiv:2310.0045

Cone Beam em Endodontia

Trabalho apresentado à Universidade Fernando Pessoa como parte dos requisitos para obtenção do grau de Mestre em Medicina DentáriaA imagiologia como uma área de interesse à qual se recorre frequentemente em Medicina Dentária, tem vindo a evoluir muito nos últimos anos apresentando novas tecnologias. A Tomografia Computorizada de Feixe Cónico (CBCT) é uma dessas tecnologias mais recentes, que possibilita a visualização de imagens em três dimensões das estruturas dentárias e das estruturas ósseas adjacentes. Situações como identificação de canais radiculares “anormais” em quantidade e morfologia, detecção de fracturas radiculares verticais, avaliação do processo de recuperação pós tratamento, poderão ser melhor e mais facilmente identificadas e tratadas com esta nova opção imagiológica. O objectivo deste trabalho é analisar o uso da CBCT em Endodontia. Para isso recorreu-se a uma pesquisa na base de dados online PubMed e Scielo, limitando a pesquisa a publicações feitas após o ano 2008 inclusivé, de onde resultou a selecção de 42 artigos. Com a realização deste trabalho foi possível concluir que o uso CBCT em Endodontia é de facto uma mais-valia, constituindo uma excelente ferramenta de diagnóstico. Imaging, as an area of interest which is frequently used by dentistry, has evolved in recent years featuring new technologies. Cone Beam Computed Tomography (CBCT) is one of these newer technologies, which enables the visualization of three-dimensional images of dental structures and adjacent bone tissue. Situations as identification of abnormal number and morphology of root canals, detection of vertical root fractures, evaluation of healing process after treatment, may be better and more easily identified and dealt with this new imaging option. The aim of this study, is to analyze the use of CBCT in Endodontics. Online search was performed on PubMed and Scielo database, limiting the search to publications made after the year 2008 inclusive. This resulted in the selection of 42 articles. With this study, it was concluded that the use of CBCT in Endodontics is indeed a great asset, making it an excellent diagnosis tool

Robust dynamical invariants in sequential neural activity

By studying different sources of temporal variability in central pattern generator (CPG) circuits, we unveil fundamental aspects of the instantaneous balance between flexibility and robustness in sequential dynamics -a property that characterizes many systems that display neural rhythms. Our analysis of the triphasic rhythm of the pyloric CPG (Carcinus maenas) shows strong robustness of transient dynamics in keeping not only the activation sequences but also specific cycle-by-cycle temporal relationships in the form of strong linear correlations between pivotal time intervals, i.e. dynamical invariants. The level of variability and coordination was characterized using intrinsic time references and intervals in long recordings of both regular and irregular rhythms. Out of the many possible combinations of time intervals studied, only two cycle-by-cycle dynamical invariants were identified, existing even outside steady states. While executing a neural sequence, dynamical invariants reflect constraints to optimize functionality by shaping the actual intervals in which activity emerges to build the sequence. Our results indicate that such boundaries to the adaptability arise from the interaction between the rich dynamics of neurons and connections. We suggest that invariant temporal sequence relationships could be present in other networks, including those shaping sequences of functional brain rhythms, and underlie rhythm programming and functionalityThis work has been supported by Spanish grants MINECO DPI2015-65833-P, TIN2017-84452-R, PGC2018-095895-B-I00 (http:// www.mineco.gob.es/), and ONRG grant N62909-14-1-N279