How to stimulate a myelinated axon at a consistent frequency?

[XiaolanWu]

Hi everyone,

I’m working on the myelinated axon model and would like to stimulate the axon with a consistent frequency (e.g. 10 Hz or 100 Hz) for a defined period of time.

What would be the best way to implement this? Would you recommend using repeated current-clamp pulses, or is there a built-in way to specify stimulation frequency and duration?

For example, I would like to generate a train of stimuli at 100 Hz for 1 second, with each stimulus reliably triggering an action potential.

Any suggestions or example code would be really appreciated. Thanks!

[Neuro-Admin]

Hi Xiaolan,

For the myelinated axon model, I would use repeated short current-clamp pulses at the soma or axon initial segment.

For example, **100 Hz for 1 second** means one stimulus every **10 ms**, giving 100 stimuli in total. Each pulse should be short (for example 0.5–1 ms) and sufficiently strong to reliably trigger one action potential.

In NEURON, the simplest approach is to use an `IClamp` and control its amplitude as a function of time using `Vector.play()`. This gives precise control over frequency, pulse duration, and total stimulation time.

For example, conceptually:

```python
frequency = 100 # Hz
period = 1000/frequency # 10 ms
duration = 1000 # ms
pulse_width = 0.5 # ms
```

Then generate a current pulse every 10 ms for 1000 ms.

`NetStim` is useful when you want a regular train of events driving a synaptic mechanism (`interval = 10 ms`, `number = 100`, `noise = 0`), but it does not directly provide current-clamp pulses. For direct electrical stimulation of the neuron, I would therefore use `IClamp`.

One important point for the myelinated axon model: do not only check that the stimulus generates 100 somatic spikes. Also record membrane voltage at the distal end of the axon. At high frequencies, especially when changing myelin or Kir4.1 parameters, the soma may continue firing while some action potentials fail to propagate through the myelinated axon.

So for a 100 Hz test I would use:

* frequency = 100 Hz
* interval = 10 ms
* stimulation duration = 1 s
* number of pulses = 100
* pulse width ≈ 0.5–1 ms
* amplitude = adjusted to give one reliable AP per pulse

I can also add this as a stimulation option directly to the BRAINCELL myelinated-axon module if needed.
Leonid

[XiaolanWu]

Thanks, this is really helpful! I will give the IClamp approach a try and check the AP propagation at the distal axon as well. Having this as an option in the BRAINCELL module would also be really useful. Thanks!