L5 pyramidal neuron myelination increases analog-digital facilitation extent (Zbili & Debanne 2020)

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Analog-digital facilitations (ADFs) correspond to a class of phenomena describing how subthreshold variations of the presynaptic membrane potential influence the synaptic transmission. ADFs rely on the propagation of somatic membrane potential fluctuations to the presynaptic bouton where they modulate ion channels availability, inducing modifications of the presynaptic spike waveform, and threfore modifying the neurotransmitter release. In this simulation, we show that myelination can promote the propagation of somatic voltage subtheshold fluctuations into the axon, allowing the ADFs to impact distal presynaptic bouton (up to 3mm from the soma).
1 . Zbili M, Debanne D (2020) Myelination increases the spatial extent of analog-digital modulation of synaptic transmission: a modeling study Frontiers in Cellular Neuroscience 14:40
Model Information (Click on a link to find other models with that property)
Model Type: Axon;
Brain Region(s)/Organism: Neocortex;
Cell Type(s): Neocortex L5/6 pyramidal GLU cell; Myelinated neuron;
Gap Junctions:
Simulation Environment: NEURON;
Model Concept(s): Action Potentials;
Implementer(s): Zbili, Mickael [zbili.mickael at gmail.com];
Search NeuronDB for information about:  Neocortex L5/6 pyramidal GLU cell;
This is the readme for the models associated with the paper:

Zbili M, Debanne D (2020) Myelination increases the spatial extent of
analog-digital modulation of synaptic transmission: a modeling study
Frontiers in Cellular Neuroscience 14:40

These NEURON files were contributed by M Zbili.

Here is an excerpt from the Materials and Methods section of the paper
(please see the paper and code for details):

"A multi-compartment model of a 36 days-old rat L5 pyramidal
neuron was simulated with NEURON 7.6. The neuronal morphology
was taken from a reconstructed neuron by Hay et al.
(2011) available on Neuromorpho.org (Ascoli et al., 2007;
Neuromorpho ID: NMO_07763; Neuron Name: C080418A-1-

To run the model, compile the mod files and run the fig hoc files. The fig2_3.hoc file
reproduces the main results of fig 2 and 3 from the paper (extension of dADF and hADF
spatial extent by myelination). The fig4.hoc file reproduces the main results of 
fig 4 from the paper (weak influence of internodes length on dADF and hADF spatial extent).
The fig5.hoc file reproduces the main results of  fig 5 from the paper (great influence of 
myelin wraps number on dADF and hADF spatial extent).
Note that this files take a long time to compute (more than 20 muntes for fig5.hoc). Therefore,
you can find the screenshots of the results in jpeg format.

Otherwise the files unmyelinated_axon.hoc, hybrid_axon.hoc, myelinated_axon_1.hoc,
myelinated_axon_2.hoc, myelinated_axon_3.hoc, myelinated_axon_4.hoc, myelinated_axon_5.hoc,
myelinated_axon_6.hoc and myelinated_axon_7.hoc correspond to the different models
used in the paper (see Table 1 and 2 of the paper for full description). There are used in the fig
hoc files. Briefly, the somato-dendritic compartments morphology and biophysics are identical in 
all the models. The axonal collaterals morphology and biophysics are also identical.
The difference between the models are : 1) the presence or abscence of myelin
at the internodes of the main axon 2) the lengths of the internodes and 3) the number of 
myelin wraps ensheating the internodes. As explained in the paper, when the internodes are
myelinated, the nodes of Ranvier present high density of Nav and Kv channels to insure
spike propagation. The exact density of  Nav and Kv channels at nodes of Ranvier has been set
to presever AP waveform identical in all models when it is emitted from the resting membrane
potential (see paper for full explanation).


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