1,029 research outputs found
Synchronous Behavior of Two Coupled Electronic Neurons
We report on experimental studies of synchronization phenomena in a pair of
analog electronic neurons (ENs). The ENs were designed to reproduce the
observed membrane voltage oscillations of isolated biological neurons from the
stomatogastric ganglion of the California spiny lobster Panulirus interruptus.
The ENs are simple analog circuits which integrate four dimensional
differential equations representing fast and slow subcellular mechanisms that
produce the characteristic regular/chaotic spiking-bursting behavior of these
cells. In this paper we study their dynamical behavior as we couple them in the
same configurations as we have done for their counterpart biological neurons.
The interconnections we use for these neural oscillators are both direct
electrical connections and excitatory and inhibitory chemical connections: each
realized by analog circuitry and suggested by biological examples. We provide
here quantitative evidence that the ENs and the biological neurons behave
similarly when coupled in the same manner. They each display well defined
bifurcations in their mutual synchronization and regularization. We report
briefly on an experiment on coupled biological neurons and four dimensional ENs
which provides further ground for testing the validity of our numerical and
electronic models of individual neural behavior. Our experiments as a whole
present interesting new examples of regularization and synchronization in
coupled nonlinear oscillators.Comment: 26 pages, 10 figure
StdpC: a modern dynamic clamp
With the advancement of computer technology many novel uses of dynamic clamp have become possible. We have added new features to our dynamic clamp software StdpC (âSpike timing-dependent plasticity Clampâ) allowing such new applications while conserving the ease of use and installation of the popular earlier Dynclamp 2/4 package. Here, we introduce the new features of a waveform generator, freely programmable HodgkinâHuxley conductances, learning synapses, graphic data displays, and a powerful scripting mechanism and discuss examples of experiments using these features. In the first example we built and âvoltage clampedâ a conductance based model cell from a passive resistorâcapacitor (RC) circuit using the dynamic clamp software to generate the voltage-dependent currents. In the second example we coupled our new spike generator through a burst detection/burst generation mechanism in a phase-dependent way to a neuron in a central pattern generator and dissected the subtle interaction between neurons, which seems to implement an information transfer through intraburst spike patterns. In the third example, making use of the new plasticity mechanism for simulated synapses, we analyzed the effect of spike timing-dependent plasticity (STDP) on synchronization revealing considerable enhancement of the entrainment of a post-synaptic neuron by a periodic spike train. These examples illustrate that with modern dynamic clamp software like StdpC, the dynamic clamp has developed beyond the mere introduction of artificial synapses or ionic conductances into neurons to a universal research tool, which might well become a standard instrument of modern electrophysiology
Dynamics of synaptically coupled integrate-and-fire-or-burst neurons
The minimal integrate-and-fire-or-burst (IFB) neuron model reproduces the salient features of
experimentally observed thalamocortical (TC) relay neuron response properties, including the tem-
poral tuning of both tonic spiking (i.e., conventional action potentials) and post-inhibitory rebound
bursting mediated by a low-threshold calcium current. In this paper we consider networks of IFB
neurons with slow synaptic interactions and show how the dynamics may be described with a
smooth firing rate model. When the firing rate of the IFB model is dominated by a refractory
process the equations of motion simplify and may be solved exactly. Numerical simulations are
used to show that a pair of reciprocally interacting inhibitory spiking IFB TC neurons supports
an alternating rhythm of the type predicted from the firing rate theory. A change in a single
parameter of the IFB neuron allows it to fire a burst of spikes in response to a depolarizing signal,
so that it mimics the behavior of a reticular (RE) cell. Within a continuum model we show that
a network of RE cells with on-center excitation can support a fast traveling pulse. In contrast a
network of inhibitory TC cells is found to support a slowly propagating lurching pulse
Clique of functional hubs orchestrates population bursts in developmentally regulated neural networks
It has recently been discovered that single neuron stimulation can impact
network dynamics in immature and adult neuronal circuits. Here we report a
novel mechanism which can explain in neuronal circuits, at an early stage of
development, the peculiar role played by a few specific neurons in
promoting/arresting the population activity. For this purpose, we consider a
standard neuronal network model, with short-term synaptic plasticity, whose
population activity is characterized by bursting behavior. The addition of
developmentally inspired constraints and correlations in the distribution of
the neuronal connectivities and excitabilities leads to the emergence of
functional hub neurons, whose stimulation/deletion is critical for the network
activity. Functional hubs form a clique, where a precise sequential activation
of the neurons is essential to ignite collective events without any need for a
specific topological architecture. Unsupervised time-lagged firings of
supra-threshold cells, in connection with coordinated entrainments of
near-threshold neurons, are the key ingredients to orchestrateComment: 39 pages, 15 figures, to appear in PLOS Computational Biolog
Mecanismos de codificaciĂłn y procesamiento de informaciĂłn en redes basadas en firmas neuronales
Tesis doctoral inĂ©dita leĂda en la Universidad AutĂłnoma de Madrid, Escuela PolitĂ©cnica Superior, Departamento de TecnologiÌa ElectroÌnica y de las Comunicaciones. Fecha de lectura: 21-02-202
Autoregressive Point-Processes as Latent State-Space Models: a Moment-Closure Approach to Fluctuations and Autocorrelations
Modeling and interpreting spike train data is a task of central importance in
computational neuroscience, with significant translational implications. Two
popular classes of data-driven models for this task are autoregressive Point
Process Generalized Linear models (PPGLM) and latent State-Space models (SSM)
with point-process observations. In this letter, we derive a mathematical
connection between these two classes of models. By introducing an auxiliary
history process, we represent exactly a PPGLM in terms of a latent, infinite
dimensional dynamical system, which can then be mapped onto an SSM by basis
function projections and moment closure. This representation provides a new
perspective on widely used methods for modeling spike data, and also suggests
novel algorithmic approaches to fitting such models. We illustrate our results
on a phasic bursting neuron model, showing that our proposed approach provides
an accurate and efficient way to capture neural dynamics
Acetylcholine neuromodulation in normal and abnormal learning and memory: vigilance control in waking, sleep, autism, amnesia, and Alzheimer's disease
This article provides a unified mechanistic neural explanation of how learning, recognition, and cognition break down during Alzheimer's disease, medial temporal amnesia, and autism. It also clarifies whey there are often sleep disturbances during these disorders. A key mechanism is how acetylcholine modules vigilance control in cortical layer
Dynamical principles in neuroscience
Dynamical modeling of neural systems and brain functions has a history of success over the last half century. This includes, for example, the explanation and prediction of some features of neural rhythmic behaviors. Many interesting dynamical models of learning and memory based on physiological experiments have been suggested over the last two decades. Dynamical models even of consciousness now exist. Usually these models and results are based on traditional approaches and paradigms of nonlinear dynamics including dynamical chaos. Neural systems are, however, an unusual subject for nonlinear dynamics for several reasons: (i) Even the simplest neural network, with only a few neurons and synaptic connections, has an enormous number of variables and control parameters. These make neural systems adaptive and flexible, and are critical to their biological function. (ii) In contrast to traditional physical systems described by well-known basic principles, first principles governing the dynamics of neural systems are unknown. (iii) Many different neural systems exhibit similar dynamics despite having different architectures and different levels of complexity. (iv) The network architecture and connection strengths are usually not known in detail and therefore the dynamical analysis must, in some sense, be probabilistic. (v) Since nervous systems are able to organize behavior based on sensory inputs, the dynamical modeling of these systems has to explain the transformation of temporal information into combinatorial or combinatorial-temporal codes, and vice versa, for memory and recognition. In this review these problems are discussed in the context of addressing the stimulating questions: What can neuroscience learn from nonlinear dynamics, and what can nonlinear dynamics learn from neuroscience?This work was supported by NSF Grant No. NSF/EIA-0130708, and Grant No. PHY 0414174; NIH Grant No. 1 R01 NS50945 and Grant No. NS40110; MEC BFI2003-07276, and FundaciĂłn BBVA
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