3,713 research outputs found
Phase synchronization of coupled bursting neurons and the generalized Kuramoto model
Bursting neurons fire rapid sequences of action potential spikes followed by
a quiescent period. The basic dynamical mechanism of bursting is the slow
currents that modulate a fast spiking activity caused by rapid ionic currents.
Minimal models of bursting neurons must include both effects. We considered one
of these models and its relation with a generalized Kuramoto model, thanks to
the definition of a geometrical phase for bursting and a corresponding
frequency. We considered neuronal networks with different connection topologies
and investigated the transition from a non-synchronized to a partially
phase-synchronized state as the coupling strength is varied. The numerically
determined critical coupling strength value for this transition to occur is
compared with theoretical results valid for the generalized Kuramoto model.Comment: 31 pages, 5 figure
Homeostatic plasticity and external input shape neural network dynamics
In vitro and in vivo spiking activity clearly differ. Whereas networks in
vitro develop strong bursts separated by periods of very little spiking
activity, in vivo cortical networks show continuous activity. This is puzzling
considering that both networks presumably share similar single-neuron dynamics
and plasticity rules. We propose that the defining difference between in vitro
and in vivo dynamics is the strength of external input. In vitro, networks are
virtually isolated, whereas in vivo every brain area receives continuous input.
We analyze a model of spiking neurons in which the input strength, mediated by
spike rate homeostasis, determines the characteristics of the dynamical state.
In more detail, our analytical and numerical results on various network
topologies show consistently that under increasing input, homeostatic
plasticity generates distinct dynamic states, from bursting, to
close-to-critical, reverberating and irregular states. This implies that the
dynamic state of a neural network is not fixed but can readily adapt to the
input strengths. Indeed, our results match experimental spike recordings in
vitro and in vivo: the in vitro bursting behavior is consistent with a state
generated by very low network input (< 0.1%), whereas in vivo activity suggests
that on the order of 1% recorded spikes are input-driven, resulting in
reverberating dynamics. Importantly, this predicts that one can abolish the
ubiquitous bursts of in vitro preparations, and instead impose dynamics
comparable to in vivo activity by exposing the system to weak long-term
stimulation, thereby opening new paths to establish an in vivo-like assay in
vitro for basic as well as neurological studies.Comment: 14 pages, 8 figures, accepted at Phys. Rev.
Computational modeling of spike generation in serotonergic neurons of the dorsal raphe nucleu
We consider here a single-compartment model of these neurons which is capable
of describing many of the known features of spike generation, particularly the
slow rhythmic pacemaking activity often observed in these cells in a variety of
species. Included in the model are ten kinds of voltage dependent ion channels
as well as calcium-dependent potassium current. Calcium dynamics includes
buffering and pumping. In sections 3-9, each component is considered in detail
and parameters estimated from voltage clamp data where possible. In the next
two sections simplified versions of some components are employed to explore the
effects of various parameters on spiking, using a systematic approach, ending
up with the following eleven components: a fast sodium current , a
delayed rectifier potassium current , a transient potassium current
, a low-threshold calcium current , two high threshold calcium
currents and , small and large conductance potassium currents
and , a hyperpolarization-activated cation current , a
leak current and intracellular calcium ion concentration .
Attention is focused on the properties usually associated with these neurons,
particularly long duration of action potential, pacemaker-like spiking and the
ramp-like return to threshold after a spike. In some cases the membrane
potential trajectories display doublets or have kinks or notches as have been
reported in some experimental studies. The computed time courses of and
during the interspike interval support the generally held view of a
competition between them in influencing the frequency of spiking. Spontaneous
spiking could be obtained with small changes in a few parameters from their
values with driven spiking.Comment: The abstract has been truncate
In vivo measurements with robust silicon-based multielectrode arrays with extreme shaft lengths
In this paper, manufacturing and in vivo testing
of extreme-long Si-based neural microelectrode arrays are presented. Probes with different shaft lengths (15–70 mm) are formed by deep reactive ion etching and have been equipped with platinum electrodes of various configurations. In vivo measurements on rats indicate good mechanical stability, robust implantation, and targeting capability. High-quality signals have been recorded from different locations of the cerebrum of the rodents. The accompanied tissue damage is characterized by histology
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