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Published on: August 30, 2007
A new cellular mechanism for coupling inputs arriving at different cortical layers
M E Larkum1, J J Zhu, B Sakmann
1Abt. Zellphysiologie, Max-Planck-Institut für Medizinische Forschung, Heidelberg, Germany. mlarkum@sunny.mpimf-heidelberg.mpg.de
Nature
|April 7, 1999
Summary
Layer 5 pyramidal neurons initiate action potentials in both axons and dendrites. A back-propagating action potential and distal dendritic input together enable calcium action potential initiation, linking inputs across cortical layers.
Area of Science:
- Neuroscience
- Computational Neuroscience
Background:
- Pyramidal neurons in layer 5 of the neocortex possess unique dual sites for action potential initiation: axonal and dendritic.
- Distal dendritic inputs typically attenuate significantly before reaching the axon, requiring a high threshold for dendritic calcium action potential initiation.
Purpose of the Study:
- To investigate the interaction between back-propagating action potentials and distal dendritic inputs in pyramidal neurons.
- To elucidate the mechanism by which distal inputs influence action potential generation in layer 5 cortical neurons.
Main Methods:
- Electrophysiological recordings in layer 5 pyramidal neurons.
- Stimulation protocols to evoke back-propagating action potentials and distal dendritic inputs.
- Analysis of calcium action potential initiation and axonal action potential bursts.
Main Results:
- A single back-propagating sodium action potential facilitates dendritic calcium action potential initiation when coinciding with distal excitatory input within milliseconds.
- Inhibitory dendritic input can effectively block dendritic calcium action potential initiation and subsequent axonal bursts.
- Distal postsynaptic potentials exert greater control over action potential initiation than predicted by electrotonic distance.
Conclusions:
- Coincidence detection between back-propagating action potentials and distal excitatory postsynaptic potentials provides a novel mechanism for associative learning in cortical output neurons.
- This mechanism allows layer 5 pyramidal neurons to integrate inputs arriving at different cortical layers, influencing network computations.
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