Wyniki wyszukiwania - BazTech

1

Susceptibility of switching between in-phase and anti-phase patterns in the network of relaxation oscillators

Olejarczyk E., Ostaszewski H., Meyrand P., Bem T.

Biocybernetics and Biomedical Engineering

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2014

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Vol. 34, no. 4

250--257

EN

Neural networks composed of two or four cells with combined, electrical and inhibitory, synapses and realized for various network topologies were examined. The aim of this study was to determine a set of phases of oscillatory cycle in which different patterns of activity, characteristic for such networks, can be switched under an external stimulus. In particular, we studied susceptibility of switching between in-phase (IP) and anti-phase (AP) patterns (and vice versa). Our results demonstrate that windows of switching between patterns are similar for networks with electrical and mixed synapses and, in general, relatively independent of the network topology. The only effect of the network topology is an increase of the robustness of the AP pattern in networks of ring-like connectivity. The switching window width and thereby the robustness of the transitions between patterns decreases with the increase of the electrical coupling strength.

2

Utilization of FraDIA for Development of Robotic Vision Subsystems on the Example of Checkers’ Playing Robot

Kornuta T., Bem T., Winiarski T.

Machine Graphics and Vision

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2011

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Vol. 20, No. 4

495-520

EN

The paper presents FraDIA, a framework facilitating the creation of vision systems, that can operate as a stand–alone application as well as play a role of a vision subsystem for robotic controllers. The article describes motivations leading to the tool creation, its structure and a method of integration with a MRROC++ system, enabling the development of a robot controllers with visual feedback. The usefulness of the framework is demonstrated on the example of a robot playing checkers. In the application, FraDIA was used to implement two different vision subsystems, and the control system exhibited two behaviors utilizing visual information in two totally different ways: passive, responsible for monitoring the state of the game, and active, in which vision was utilized during the manipulator motion for localization of a pawn to be grasped. Regarding the complexity of the system, a specification method based on agents and transition function was used. The method, consisting of mathematical formulas supplemented by data flow diagrams, enables the reader to understand both the system structure and its behavior.

3

Zastosowanie wizyjnej struktury ramowej FraDIA w aplikacjach robotycznych. Część II: Aplikacje

Bem T., Kornuta T., Winiarski T.

Prace Naukowe Politechniki Warszawskiej. Elektronika

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2010

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z. 175, t. 2

573-582

PL

W poniższej, drugiej części artykułu omówiono sposób integracji struktur ramowych MRROC++ i FraDIA w sterowniki aplikacji robotycznych wykorzystujących informacje wizyjną. Pokrótce zaprezentowano kilka wybranych aplikacji robotycznych skonstruowanych z wykorzystaniem obu struktur. W detalach omówiono sterownik robota grającego w warcaby, poświęcając specjalną uwagę algorytmowi realizującemu chwytanie pionów z planszy, na który składają się serwomechanizm wizyjny oraz sterowanie pozycyjno-siłowe.

EN

The second part of the article describes a method of integration of the MRROC++ and the FraDIA frameworks. While the first framework enables rapid creation of robotic controllers, the second retrieves and process the visual information. The integration of these two allows to create a robot controllers with a vision subsystems. The article shallowly presents selected robotic application utilizing presented approach and in the end goes into details of a complex robotic system which can play checkers with a human opponent. A special attention is put on pawn approach and grasping tasks, which process visual information during the visual servoing stage and utilizes force sensor for contact detection and pawn grasping.

4

Multi-stability of in-phase and anti-phase activity patterns in neural networks with inhibitory and electrical synapses

Ostaszewski H., Meyrand P., Branchereau P., Hallam J., Bem T.

Biocybernetics and Biomedical Engineering

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2010

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Vol. 30, no. 3

3-17

EN

As shown in modeling and experimental studies, network comprised of spiking cells interconnected by inhibitory and electrical synapses may express different activity patterns without any change of the network topology or parameters. In this study we confirm robust-ness of this phenomenon by demonstrating multi-stability of hybrid networks consisting of biological neurons of different types. Moreover we show here, using relaxation oscillator model cells, that multi-stability of in-phase (IP) and anti-phase (AP) patterns may be expressed in a network fully connected by instantaneous synaptic inhibition and electrical coupling independently of the network size. In such a network a stimulus of a given profile, consisting of depolarizing and hyperpolarizing signals sent to different subpopulations of cells, can evoke direct switching between IP and AP patterns. We also show that similar phenomenon occurs in more realistic network models with sparse connectivity. Our results suggest that transient signals if arriving in a proper time window may instantaneously reconfigure a given spatio-temporal activity pattern expressed by the network into another stable pattern without any change of the network properties.

5

Electrical coupling and bistability in inhibitory neuronal networks

Bem T., Hallam J., Meyrand P., Rinzel J.

Biocybernetics and Biomedical Engineering

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2006

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Vol. 26, no. 2

3-14

EN

The role of gap junction-mediated electrical coupling in oscillatory networks is not yet fuIly understood. Such coupling is widespread in developing nervous systems and in many structures of the adult brain where it coexists with synaptic inhibition. Our results, both modeling and experimental, indicate that the effect of electrical coupling in networks of rhythmic inhibitory neurons is crucially dependent on the cells' duty cycle. In the Stomatogastric Nervous System, in which ceIls with large duty cycle are interconnected by reciprocal inhibition, electrical coupling may be responsible for masking adult-like properties of the embryonic network by coordinating the neuronal activity into a single rhythm with different phases. In a two-ceIl half-center oscillator model short duty cycle destabilizes antiphase activity which can be re-established by adding electrical coupling. Moreover, such a network expresses bistability of the in-phase and anti-phase patterns in some range of coupling strengths. AIso in a large-scale model network, in which ceIls are interconnected electrically and by synaptic inhibition, multistability of the in-phase and different anti-phase patterns may occur. A possible function of the multistability in the controI of movement is discussed.