How the function is applied in connection

[xchoo]

Hi @corricvale, and welcome back to the Nengo forums!

To answer your question:

@corricvale

I read that when the function is used in the connection, the pre object must be an ensemble. If that is the case, is the order that you apply the function as follows?

1. the spiking signals from the neurons of the pre ensemble are first decoded through the connection synapse (0.1 in the example)
2. then the function is applied to the decoded values.
3. The values after the function computation are the output of the connection.

That’s not actually how the function works. In this post, I walk through several ensemble & connection properties, and the important line that pertains to your question is this:

@xchoo

The transform and function parameters of a Nengo connection are fairly similar and both serve to provide Nengo with information on how to solve for the connection’s decoders.

To summarize, the process by which Nengo uses to obtain the decoders is as follows:

• For some set of evaluation points, obtain the corresponding neural activity
• For the same set of evaluation points, obtain a set of “output” data determined by the function and transform specified for the connection.
• Solve for decoders that, when applied to the neural response curves, maps the evaluation points to the desired set of output data.

I should note that in Nengo, the decoders are associated with the connection object that is “computing” the function. I.e., you can have multiple decoders per Nengo ensemble (if you have multiple connections originating from that ensemble).