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### Frequency response function

Posted: **Wed Oct 24, 2018 8:18 pm**

by **plasticity**

Hi

I am new to NEURON. Does it have a means for calculating the frequency response function between input (injected curren) and output (membrane potential) sites for subthreshold stimuli using a linear model?

Thank you!

### Re: Frequency response function

Posted: **Wed Oct 24, 2018 9:44 pm**

by **ted**

Does it have a means for calculating the frequency response function between input (injected curren) and output (membrane potential) sites for subthreshold stimuli using a linear model?

I don't think your question has an answer. What does it mean to talk about the frequency of a cell's response to a subthreshold input? By definition, a subthreshold input elicits no spikes. If a stimulus fails to make a cell fire spikes, how can one speak of the frequency of the stimulated cell's response? Besides, if the cell fires no spikes, then none of that cell's targets will ever know that it received an input.

### Re: Frequency response function

Posted: **Wed Oct 24, 2018 10:38 pm**

by **plasticity**

Ted

Subthreshold systems are often described by linearized equations. At steady state they will oscillating at the driving frequency of the input current. No spikes are produced. The Fourier transform of the response is called the frequency response of the system.

### Re: Frequency response function

Posted: **Wed Oct 24, 2018 11:31 pm**

by **ted**

An interesting example of miscommunication. I've been thinking a lot about spiking networks lately, so I'm "stuck on spikes"--when I think of a cell's "frequency response" to an input, or the "output" that it might generate in response to an input, what comes to mind is F-I curves, and that implies spiking. So much for that.

NEURON's Impedance class will do what you want. In particular, you'll want to use it to compute transfer impedance. Read about the Impedance class in the Programmer's Reference, and especially the details about its compute() method.

NEURON has a GUI tool that can be used to compute impedances. Very nice for interactive use, especially with anatomically complex models, as a way to tune up ones intuition. For a tutorial on how to use it, download

https://www.neuron.yale.edu/ftp/neuron/ ... course.zip
unzip it, then

cd course/impedance_class

and finally use a web browser to examine impedance_class.html

If you have a model that does not play nicely with Impedance.compute(), you might find it useful to use izap--see

https://www.neuron.yale.edu/ftp/ted/neuron/izap.zip

### Re: Frequency response function

Posted: **Thu Oct 25, 2018 1:23 am**

by **plasticity**

Thanks Ted

I will be taking a look very soon. This is great!

Yep, I figured you had spikes on your mind hence my gentle nudge back toward the subthreshold and linear systems.