A few questions about the DiehlAndCook2015 model

[rafaelblevin821]

Hi, I just have a few questions about the DiehlAndCook2015 model that I am trying to understand.

# Layers
        input_layer = Input(
            n=self.n_inpt, shape=self.inpt_shape, traces=True, tc_trace=20.0
        )
        exc_layer = DiehlAndCookNodes(
            n=self.n_neurons,
            traces=True,
            rest=-65.0,
            reset=-60.0,
            thresh=-52.0,
            refrac=5,
            tc_decay=100.0,
            tc_trace=20.0,
            theta_plus=theta_plus,
            tc_theta_decay=tc_theta_decay,
        )
        inh_layer = LIFNodes(
            n=self.n_neurons,
            traces=False,
            rest=-60.0,
            reset=-45.0,
            thresh=-40.0,
            tc_decay=10.0,
            refrac=2,
            tc_trace=20.0,
        )

I know the documentation briefly describes the parameters, but I'm still unsure how they are implemented.

I am particularly interested in the parameters reset, tc_decay, and tc_trace.
Why is a reset value used when we have a resting potential value?
If tc_decay is 100 by default, does that not limit the number of spikes to <4 if the simulation time is, say, 500?
Why is tc_trace needed when the tc_decay is in place?

Also, are these all callable arguments from the script that can be changed if necessary?

I'd be grateful for any insight on this.

[Hananel-Hazan]

I know the documentation briefly describes the parameters, but I'm still unsure how they are implemented.

The implementation of the DiehlAndCookNodes neuron can be found here and the implementation of the LIFNodes can be found here, you can find an answers to most of your questions.

In brief, the code give you an option to use two different resting Vmem one for Post-spike reset and the other for rest value that use to calculate the decaying of the Vmem during inactivity. You can use the two values if you need or set them to the same value if you dont need them.

[rafaelblevin821]

Hi @Hananel-Hazan thanks. That clears up the rest and reset differences.

Can you tell me the difference between tc_decay and tc_trace?

There is a one-line description in the documentation of each, but it is not very clear. Thanks.

[rafaelblevin821]

@Hananel-Hazan, sorry, scratch that. I think I've understood the differences now.

Please correct me if I am wrong, but tc_decay is the decay time of the spike to reset or rest, while tc_trace is the time that spike trace history remains to be used for calculations in weight updates. Is this correct?

[Hananel-Hazan]

Yes, that is correct