Interspike interval: Difference between revisions

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One of the most important ways by which neurons in the brain carry information is by means of electrical signals. At rest, neurons have a ‘[[resting membrane potential]]’ of typically about -70 mV: this is the potential difference between the inside of the cell and the external environment. However, this membrane potential is continually being disturbed by the chemical signals (''[[neurotransmitters]]'') released by other neurons. In the brain a neuron might be receiving inputs from as many as ten thousand other neurons, these inputs usually consist of brief excitations (EPSPs; [[excitatory post-synaptic potential]]s) or of brief inhibitions (IPSPs; [[inhibitory post-synaptic potential]]s) that either make the membrane less negative ([[depolarisation]]s) or more negative ([[hyperpolarisation]]s). If a neuron becomes sufficiently depolarised, perhaps because of a flurry of EPSPs, then the membrane potential may reach the critical threshold for triggering an [[action potential]] (commonly called a ‘’spike’’). An action potential is a very large and rapid rise in the cell membrane potential, that lasts for only about one millisecond before the membrane potential returns again to around its resting potential. These spikes are propagated along the [[axon]]s of a neuron, to reach the nerve terminals, where they can trigger the release of chemical messengers to affect other neurons.
The '''interspike interval''' is the time between subsequent [[action potential]]s (also known as ''spikes'') of a [[neuron]], or a group average thereof.
[[Image:Spiketimes.png|thumb|300 px| Schematic showing measurement of successive intervals (t1, t2, t3, etc) between successive spikes of electrical activity recorded from a neuron]]
Thus spikes are a very important way by which neurons in the brain carry information. The spike itself is an all-or-none phenomenon, so information is coded not in the amplitude of a spike but in the timing of spikes. Accordingly, [[electrophysiologist]]s, who study the electrical behaviour of neurons, are interested in the patterning of spikes in particular neurons.  


The patterning of spike activity is influenced by three things:
Action potentials are propagated along the [[axon]]s of a neuron, to reach the nerve terminals, where they can trigger the release of [[chemical messenger]]s to affect other neurons.
[[Image:Spiketimes.png|thumb|300 px| Schematic showing measurement of successive intervals (t1, t2, t3, etc) between successive spikes of electrical activity recorded from a neuron.]]
Thus spikes are a very important way by which neurons in the brain carry information. The spike itself is an all-or-none phenomenon, so information is coded not in the amplitude of a spike but in the timing of spikes. Accordingly, [[electrophysiologist]]s, who study the electrical behaviour of neurons, are interested in the patterning of spikes in particular neurons, which they typically analyze by way of an [[interspike interval histogram]].
 
The patterning of spike activity is influenced by three factors:
a) the intrinsic properties of the neuron, especially the properties of its membrane. The neurons in the brain are very diverse; there are very many different subpopulations of neurons that have quite different intrinsic properties
a) the intrinsic properties of the neuron, especially the properties of its membrane. The neurons in the brain are very diverse; there are very many different subpopulations of neurons that have quite different intrinsic properties
b) network interactions, because spike activity in one neuron might have feedback effects on that neuron because of the changes that it produces in reciprocally connected neurons
b) network interactions, because spike activity in one neuron might have feedback effects on that neuron because of the changes that it produces in reciprocally connected neurons
and  
and  
c) the nature of the inputs to that neuron.
c) the nature of the inputs to that neuron.

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The interspike interval is the time between subsequent action potentials (also known as spikes) of a neuron, or a group average thereof.

Action potentials are propagated along the axons of a neuron, to reach the nerve terminals, where they can trigger the release of chemical messengers to affect other neurons.

Schematic showing measurement of successive intervals (t1, t2, t3, etc) between successive spikes of electrical activity recorded from a neuron.

Thus spikes are a very important way by which neurons in the brain carry information. The spike itself is an all-or-none phenomenon, so information is coded not in the amplitude of a spike but in the timing of spikes. Accordingly, electrophysiologists, who study the electrical behaviour of neurons, are interested in the patterning of spikes in particular neurons, which they typically analyze by way of an interspike interval histogram.

The patterning of spike activity is influenced by three factors: a) the intrinsic properties of the neuron, especially the properties of its membrane. The neurons in the brain are very diverse; there are very many different subpopulations of neurons that have quite different intrinsic properties b) network interactions, because spike activity in one neuron might have feedback effects on that neuron because of the changes that it produces in reciprocally connected neurons and c) the nature of the inputs to that neuron.

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