461 research outputs found
Anticipated synchronization and the predict-prevent control method in the FitzHugh-Nagumo model system
We study the synchronization region of two unidirectionally coupled, in a
master-slave configuration, FitzHugh-Nagumo systems under the influence of
external forcing terms. We observe that anticipated synchronization is robust
to the different types of forcings. We then use the predict-prevent control
method to suppress unwanted pulses in the master system by using the
information of the slave output. We find that this method is more efficient
than the direct control method based on the master. Finally, we observe that a
perfect matching between the parameters of the master and the slave is not
necessary for the control to be efficient. Moreover, this parameter mismatch
can, in some cases, improve the control
Experimental Observation of Coherence and Stochastic Resonances in an Electronic Chua Circuit
Stochastic and coherence resonances appear in nonlinear systems subjected to
an external source of noise and are characterized by a maximum response at the
optimal value of the noise intensity. This paper shows experimentally that it
is possible to observe them in a chaotic system. To this end we have analysed
an electronic Chua circuit running in the chaotic regime and added noise to its
dynamics. In the case of coherence resonance, we observe an optimal periodicity
for the jumps between chaotic attractors, whereas in the case of stochastic
resonance we observe a maximum in the signal-to-noise ratio at the frequency of
an external sinusoidal perturbation.Comment: 6 page
Zero-lag long-range synchronization of Hodgkin-Huxley neurons is enhanced by dynamical relaying : poster presentation
Background The synchrony hypothesis postulates that precise temporal synchronization of different pools of neurons conveys information that is not contained in their firing rates. The synchrony hypothesis had been supported by experimental findings demonstrating that millisecond precise synchrony of neuronal oscillations across well separated brain regions plays an essential role in visual perception and other higher cognitive tasks [1]. Albeit, more evidence is being accumulated in favour of its role as a binding mechanism of distributed neural responses, the physical and anatomical substrate for such a dynamic and precise synchrony, especially zero-lag even in the presence of non-negligible delays, remains unclear. Here we propose a simple network motif that naturally accounts for zero-lag synchronization for a wide range of temporal delays [3]. We demonstrate that zero-lag synchronization between two distant neurons or neural populations can be achieved by relaying the dynamics via a third mediating single neuron or population. Methods We simulated the dynamics of two Hodgkin-Huxley neurons that interact with each other via an intermediate third neuron. The synaptic coupling was mediated through alpha-functions. Individual temporal delays of the arrival of pre-synaptic potentials were modelled by a gamma distribution. The strength of the synchronization and the phase-difference between each individual pairs were derived by cross-correlation of the membrane potentials. Results In the regular spiking regime the two outer neurons consistently synchronize with zero phase lag irrespective of the initial conditions. This robust zero-lag synchronization naturally arises as a consequence of the relay and redistribution of the dynamics performed by the central neuron. This result is independent on whether the coupling is excitatory or inhibitory and can be maintained for arbitrarily long time delays (see Fig. 1). Conclusion We have presented a simple and extremely robust network motif able to account for the isochronous synchronization of distant neural elements in a natural way. As opposed to other possible mechanisms of neural synchronization, neither inhibitory coupling, gap junctions nor precise tuning of morphological parameters are required to obtain zero-lag synchronized neuronal oscillation
Mechanisms of Zero-Lag Synchronization in Cortical Motifs
Zero-lag synchronization between distant cortical areas has been observed in
a diversity of experimental data sets and between many different regions of the
brain. Several computational mechanisms have been proposed to account for such
isochronous synchronization in the presence of long conduction delays: Of
these, the phenomenon of "dynamical relaying" - a mechanism that relies on a
specific network motif - has proven to be the most robust with respect to
parameter mismatch and system noise. Surprisingly, despite a contrary belief in
the community, the common driving motif is an unreliable means of establishing
zero-lag synchrony. Although dynamical relaying has been validated in empirical
and computational studies, the deeper dynamical mechanisms and comparison to
dynamics on other motifs is lacking. By systematically comparing
synchronization on a variety of small motifs, we establish that the presence of
a single reciprocally connected pair - a "resonance pair" - plays a crucial
role in disambiguating those motifs that foster zero-lag synchrony in the
presence of conduction delays (such as dynamical relaying) from those that do
not (such as the common driving triad). Remarkably, minor structural changes to
the common driving motif that incorporate a reciprocal pair recover robust
zero-lag synchrony. The findings are observed in computational models of
spiking neurons, populations of spiking neurons and neural mass models, and
arise whether the oscillatory systems are periodic, chaotic, noise-free or
driven by stochastic inputs. The influence of the resonance pair is also robust
to parameter mismatch and asymmetrical time delays amongst the elements of the
motif. We call this manner of facilitating zero-lag synchrony resonance-induced
synchronization, outline the conditions for its occurrence, and propose that it
may be a general mechanism to promote zero-lag synchrony in the brain.Comment: 41 pages, 12 figures, and 11 supplementary figure
Analytical and Numerical Studies of Noise-induced Synchronization of Chaotic Systems
We study the effect that the injection of a common source of noise has on the
trajectories of chaotic systems, addressing some contradictory results present
in the literature. We present particular examples of 1-d maps and the Lorenz
system, both in the chaotic region, and give numerical evidence showing that
the addition of a common noise to different trajectories, which start from
different initial conditions, leads eventually to their perfect
synchronization. When synchronization occurs, the largest Lyapunov exponent
becomes negative. For a simple map we are able to show this phenomenon
analytically. Finally, we analyze the structural stability of the phenomenon.Comment: 10 pages including 12 postscript figures, revtex. Additional work in
http://www.imedea.uib.es/Nonlinear . The paper with higher-resolution figures
can be obtained from
http://www.imedea.uib.es/PhysDept/publicationsDB/date.htm
Anticipating the response of excitable systems driven by random forcing
We study the regime of anticipated synchronization in unidirectionally
coupled model neurons subject to a common external aperiodic forcing that makes
their behavior unpredictable. We show numerically and by implementation in
analog hardware electronic circuits that, under appropriate coupling
conditions, the pulses fired by the slave neuron anticipate (i.e. predict) the
pulses fired by the master neuron. This anticipated synchronization occurs even
when the common external forcing is white noise.Comment: 12 pages (RevTex format
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