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Models of genetic interactions and methods of use
Title
Models of genetic interactions and methods of use.
Creator
Liebovitch, Larry S., Jirsa, Viktor K., Shehadeh, Lina A., Florida Atlantic University
Date Issued
2003-11
PURL
http://purl.flvc.org/fcla/dt/15825
Format
Document (PDF)
Relationships between the global structure of genetic networks and mRNA levels measured by cDNA microarrays
Title
Relationships between the global structure of genetic networks and mRNA levels measured by cDNA microarrays.
Creator
Liebovitch, Larry S., Shehadeh, Lina A., Jirsa, Viktor K.
Date Issued
2006-05-16
PURL
http://purl.flvc.org/fau/165446
Subject Headings
DNA microarrays, DNA--genetics, Gene Expression Regulation, DNA- protein interactions, Genetic regulation, Messenger RNA--Analysis
Format
Document (PDF)
Dynamical perception: Modeling framework, model and experiment
Title
Dynamical perception: Modeling framework, model and experiment.
Creator
Almonte, Felix, Florida Atlantic University, Jirsa, Viktor K.
Abstract/Description
Can a distributed anatomical and functional architecture serve as the basis for sufficiently complex perceptual phenomena? In addressing this question, the conceptual notion of dynamical system and its relation to other paradigms is considered including its definition. The principal goal is to develop a dynamical framework on which to ground the theoretical study of perception and other physical phenomena. As an entry point, the perceptual dynamics of auditory streaming are modeled using a...
Show moreCan a distributed anatomical and functional architecture serve as the basis for sufficiently complex perceptual phenomena? In addressing this question, the conceptual notion of dynamical system and its relation to other paradigms is considered including its definition. The principal goal is to develop a dynamical framework on which to ground the theoretical study of perception and other physical phenomena. As an entry point, the perceptual dynamics of auditory streaming are modeled using a neurally inspired dynamical model of auditory processing. Traditional approaches view streaming as a competition of streams, realized within a tonotopically organized neural network. In contrast, streaming can be viewed as a dynamic integration process involving locations (information convergence zones) other than the sensory specific neural subsystems. This process finds its realization in the synchronization of neural ensembles. Consequently, the model employs two interacting dynamical systems. The first system responds to incoming acoustic stimuli and transforms them into a spatiotemporal neural field dynamics. The second system is a classification system coupled to the neural field and evolves to a stationary state in the absence of input. The states of the classification system at any time t are identified with a single perceptual stream or multiple streams. Several results in human perception are modeled including temporal coherence and fission boundaries (van Noorden, 1975), and crossing of motions (Bregman, 1990). The model predicts phenomena such as the existence of two streams with the same pitch. So far, this has not been explained by the traditional stream competition models. A psychophysical study provides proof of existence of this phenomenon. Using set theoretical expressions on fMRI data, evidence was found showing that the percept of auditory streaming involves regions (convergence zones) other than just the primary auditory areas. This is a necessary condition for the existence of the network architecture proposed in the auditory streaming model. Networks specific and common to both amplitude and frequency streaming were identified. This lends support to models of perception conceived as interacting neural subnetworks acting as functional differentiation areas and information convergence zones for the classification of the perceptual world as suggested by the introductory question.
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Date Issued
2006
PURL
http://purl.flvc.org/fcla/dt/12201
Subject Headings
Human information processing, Perception, Cognition--Research--Methodology, Neurolinguistics
Format
Document (PDF)
Neural Information Processing Underlying Rhythmic Bimanual Coordination: Theory, Method and Experiment
Title
Neural Information Processing Underlying Rhythmic Bimanual Coordination: Theory, Method and Experiment.
Creator
Banerjee, Arpan, Jirsa, Viktor K., Florida Atlantic University
Abstract/Description
How do neuronal connectivity and the dynamics of distributed brain networks process information during bimanual coordination? Contemporary brain theories of cognitive function posit spatial, temporal and spatiotemporal network reorganization as mechanisms for neural information processing. In this dissertation, rhythmic bimanual coordination is studied as a window into neural information processing and subsequently an investigation of underlying network reorganization processes is performed....
Show moreHow do neuronal connectivity and the dynamics of distributed brain networks process information during bimanual coordination? Contemporary brain theories of cognitive function posit spatial, temporal and spatiotemporal network reorganization as mechanisms for neural information processing. In this dissertation, rhythmic bimanual coordination is studied as a window into neural information processing and subsequently an investigation of underlying network reorganization processes is performed. Spatiotemporal reorganization between effectors (limbs) is parameterized in a theoretical model via a continuously varying cross-talk parameter that represents neural connectivity. Thereby, effector dynamics during coordinated behavior is shown to be influenced by the cross-talk parameter and time delays involved in signal processing. In particular, stability regimes of coordination patterns as a function of cross-talk, movement frequency and the time delays are derived. On the methodological front , spatiotemporal reorganization of neural masses are used to simulate electroencephalographic data. A suitable choice of experimental control conditions is used to derive a paradigmatic framework called Mode Level Cognitive Subtraction (MLCS) which is demonstrated to facilitate the disambiguation between spatial and temporal components of the reorganization processes to a quantifiable degree of certainty. In the experimental section, MLCS is applied to electroencephalographic recordings during rhythmic bimanual task conditions and unimanual control conditions. Finally, a classification of reorganization processes is achieved for differing stability states of coordination: inphase (mirror) primarily entails temporal reorganization of sensorimotor networks localized during unimanual movement whereas spatiotemporal reorganization is involved during antiphase (parallel) coordination.
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Date Issued
2007
PURL
http://purl.flvc.org/fau/fd/FA00000849
Subject Headings
Neural networks (Computer science), Biological control systems, Mind and body, Cognitive psychology
Format
Document (PDF)
Theoretical and experimental studies of multisensory integration as a coupled dynamical system
Title
Theoretical and experimental studies of multisensory integration as a coupled dynamical system.
Creator
Assisi, Collins G., Florida Atlantic University, Kelso, J. A. Scott, Jirsa, Viktor K.
Abstract/Description
Perception and behavior are mediated by a widely distributed network of brain areas. Our main concern is, how do the components of the network interact in order to give us a variety of complex coordinated behavior? We first define the nodes of the network, termed functional units, as a strongly coupled ensemble of non-identical neurons and demonstrate that the dynamics of such an ensemble may be approximated by a low dimensional set of equations. The dynamics is studied in two different...
Show morePerception and behavior are mediated by a widely distributed network of brain areas. Our main concern is, how do the components of the network interact in order to give us a variety of complex coordinated behavior? We first define the nodes of the network, termed functional units, as a strongly coupled ensemble of non-identical neurons and demonstrate that the dynamics of such an ensemble may be approximated by a low dimensional set of equations. The dynamics is studied in two different contexts, sensorimotor coordination and multisensory integration. First, we treat movement coupled to the environment as a driven functional unit. Our central hypothesis is that this coupling must be minimally parametric. We demonstrate the experimental validity of this hypothesis and propose a theoretical model that explains the results of our experiment. A second example of the dynamics of functional units is evident in the domain of multisensory integration. We employ a novel rhythmic multisensory paradigm designed to capture the temporal features of multisensory integration parametrically. The relevant parameters of our experiment are the inter-onset interval between pairs of rhythmically presented stimuli and the frequency of presentation. We partition the two dimensional parameter space using subjects perception of the stimulus sequence. The general features of the partitioning are modality independent suggesting that these features depend on the coupling between the unisensory subsystems. We develop a model with coupled functional units and suggest a candidate coupling scheme. In subsequent chapters we probe the neural correlates of multisensory integration using fMRI and EEG. The results of our fMRI experiment demonstrate that multisensory integration is mediated by a network consisting of primary sensory areas, inferior parietal lobule, prefrontal areas and the posterior midbrain. Different percepts lead to the recruitment of different areas and their disengagement for other percepts. In analyzing the EEG data, we first develop a mathematical framework that allows us to differentiate between sources activated for both unisensory and multisensory stimulation from those sources activated only for multisensory stimulation. Using this methodology we show that the influences of multisensory processing may be seen at an early (40--60 ms) stage of sensory processing.
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Date Issued
2005
PURL
http://purl.flvc.org/fcla/dt/12167
Subject Headings
Intersensory effects, Perceptual-motor processes, Sensorimotor integration, Psychology, Comparative, Developmental neurobiology
Format
Document (PDF)
Neural field dynamics under vari ation of local and global connectivity and finite t ransmission speeds.
Title
Neural field dynamics under vari ation of local and global connectivity and finite t ransmission speeds.
Creator
Qubbaj, Murad R., Florida Atlantic University, Jirsa, Viktor K., Charles E. Schmidt College of Science, Department of Physics
Abstract/Description
Spatially continuous networks with heterogeneous connections are ubiquitous in biological systems, in part icular neural systems. To understand the mutual effects of locally homogeneous and globally heterogeneous connectivity, the st ability of the steady state activity of a neural field as a fun ction of its connectivity is investigated. The variation of the connectivity is operationalized through manipulation of a heterogeneous two-point connection embedded into the otherwise homogeneous...
Show moreSpatially continuous networks with heterogeneous connections are ubiquitous in biological systems, in part icular neural systems. To understand the mutual effects of locally homogeneous and globally heterogeneous connectivity, the st ability of the steady state activity of a neural field as a fun ction of its connectivity is investigated. The variation of the connectivity is operationalized through manipulation of a heterogeneous two-point connection embedded into the otherwise homogeneous connectivity matrix and by variation of connectivity strength and transmission speed. A detailed discussion of the example of the real Ginzburg-Land au equation with an embedded two-point heterogeneous connection in addition to the homogeneous coupling due to the diffusion term is performed. The system is reduced to a set of delay differential equations and the stability di agrams as a function of the time delay and the local and global coupling strengths are computed. The major finding is that the stability of the heterogeneously connected elements with a well-defined velocity defines a lower bound for the stabil ity of the entire system . Diffusion and velocity dispersion always result in increased stability. Various other local architectures represented by exponentially decaying connectivity fun ctions are also discussed. The analysis shows that developmental changes such as the myelination of the cortical large-scale fib er system generally result in the stabilization of steady state activity via oscillatory instabilities independent of the local connectivity. Non-oscillatory (Turing) instabilities are shown to be independent of any influences of time delay.
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Date Issued
2007
PURL
http://purl.flvc.org/fau/fd/FA00000873
Subject Headings
Mathematical physics, Connections (Mathematics), Superconductivity--Mathematics, Neural networks (Computer science)
Format
Document (PDF)