bursting seams


Bursting is a rapid signaling mode in neurons whereby clusters of two or more action potentials (spikes) are emitted as a single signaling event. A burst of two spikes is called a doublet, three spikes - triplet, four - quadruplet, etc. Burst mode is thought to be useful for signaling important events and routing information in the brain. In general, there are two types of bursting:

  1. Input-driven bursting, where strong excitatory inputs produce a rapid activation and burst of action potentials
  2. Intrinsic bursting, where voltage-gated ion channels intrinsic to the neuron convert brief suprathreshold inputs into long-lasting bursts of action potential output.

Some types of neurons are able to respond to current input by emitting an all- or non-burst response. This burst usually consists of a short phase of repeated action potentials, at a frequency of up to 350 Hz. This is followed by a prolonged refractory period. In contrast, neurons that fire tonically respond with action potentials at a rate proportional to the input current.

Most mathematical models of bursting can be written in the singularly perturbed form

begin{matrix} dot{x} = f(x, y) & mbox{(fast spiking)} dot{y} = mu g(x, y) & mbox{(slow modulation)} end{matrix} where x is the fast variable, a vector that simulates fast spiking of the neuron, and y is the slow variable, a vector that modulates spiking activity. A topological classification of bursters relies on the bifurcations of the fast subsystem (variable x) when the slow subsystem (variable y) is treated as a parameter.

The subiculum is an example of a brain region where the rapid transition between bursting and single-spiking is important for routing information out of the hippocampus.



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