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Updated: Jun 30, 2026
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Juxtasomal Biocytin Labeling to Study the Structure-function Relationship of Individual Cortical Neurons
Published on: February 25, 2014
Analog signalling in mammalian cortical axons
1Independent Hertie Research Group, Max-Planck-Institute for Brain Research, D-60528 Frankfurt, Germany.
Current Opinion in Neurobiology
|September 20, 2008
Summary
Neurons communicate using both digital action potentials and analog subthreshold signals that travel down axons. This hybrid code allows for more complex information processing in the brain.
Area of Science:
- Neuroscience
- Cellular Biology
- Computational Neuroscience
Background:
- The traditional understanding of neuronal communication relies on stereotyped, all-or-none action potentials.
- The role of subthreshold signal propagation within neuronal axons has been historically overlooked.
Purpose of the Study:
- To investigate the propagation of subthreshold signals along cortical axons.
- To determine if these analog axonal signals influence synaptic transmission.
Main Methods:
- Direct electrophysiological recordings from axonal structures in the hippocampus and neocortex.
- Analysis of subthreshold signal propagation and its impact on action potential-dependent neurotransmitter release.
Main Results:
- Subthreshold-graded signals were observed to propagate along axons for distances up to 1 mm.
- These analog axonal signals were found to modulate action-potential-dependent transmitter release at certain synapses.
Conclusions:
- Neuronal communication in the mammalian cortex utilizes a hybrid code, combining digital action potentials with analog axonal signals.
- This hybrid coding mechanism enhances the complexity of information processing within local cortical circuits.
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01:09Synaptic Signaling
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01:14Action Potential
Neurons communicate by firing action potentials—the electrochemical signal that is propagated along the axon. The signal results in the release of neurotransmitters at axon terminals, thereby transmitting information to the nervous system. An action potential is a specific "all-or-none" change in membrane potential that results in a rapid spike in voltage.
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01:14Action Potential
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01:41Action Potentials
Overview
01:19The Role of Ion Channels in Neuronal Computation
A postsynaptic neuron usually receives numerous impulses from several other presynaptic neurons. The axon hillock of the postsynaptic neuron integrates all these signals and determines the likelihood of firing an action potential.
Sometimes a single EPSP is strong enough to induce an action potential in the postsynaptic neuron. However, multiple presynaptic inputs must often create EPSPs around the same time for the postsynaptic neuron to be sufficiently depolarized to fire an action potential.
Sometimes a single EPSP is strong enough to induce an action potential in the postsynaptic neuron. However, multiple presynaptic inputs must often create EPSPs around the same time for the postsynaptic neuron to be sufficiently depolarized to fire an action potential.