[nengo-user] Association strength in memory and scripting codes

[Chris Eliasmith]

Hi,

Yes, you can increase relative weight by multiplying the convolution by 
a scalar when adding it into memory.  This will work for working memory. 
  I.e. doing something like:

Memory = A*B + 2*B*C

Will make the second association much stronger than the first, in the 
sense that comparing this memory to A*B or B*C, you'll get higher 
similarity with the latter.

For the second question, I'm not sure what you mean by 'specific 
pattern'.  Typically the firing pattern of populations are different 
even if they represent the same thing (because the neurons are 
different).   If you mean representation of a vector, then yes you can 
transfer to B and not C if you gate the input to C; you can use 
inhibitory gates, or multiplicative gates.  The SPA module includes 
inhibitory gating automatically, as discussed here:

http://nengo.ca/docs/html/demos/spa_sequencerouted.html

It is one of the demos that comes with the download.

There is also a 'gate' drag and drop element in the toolbar in Nengo. If 
you look at the code for that template, it shows how to construct these 
inhibitory gates.  You'll find it under /python/nef/templates/gate.py

It basically does something like this:
a = nengo.Ensemble(30, 1)
b = nengo.Ensemble(20, 1)
nengo.Connection(a, b.neuron, transform=[[-1]]*(20))

best, .c



Jessica Dinh wrote:
> Hello,
>
> I have a few questions about modeling memory in Nengo that I hoped the
> community might have answers to. First, is there a way to increase the
> relative weight of a particular concept or pattern relative to other
> patterns that are inputted into the model? For instance, I wanted the
> model to form a stronger association between two semantic pointers
> relative to two other semantic pointers in memory when the pairs are
> convolved in the model.
>
> My second question is a scripting question. Is there a sample scripting
> template that shows how a specific pattern can be transferred from one
> neural ensemble to another? For example, if I wanted a pattern to be
> transferred from ensemble A -> ensemble B, but not ensemble C that has
> connections to ensemble A.
>
> Thank you!
> Jessica
>
> --
> Dr. Jessica E. Dinh
> Industrial/Organizational Psychology
> The University of Akron
> Arts & Sciences Building, Mailbox #20
> Akron, OH 44325
> jd62 at zips.uakron.edu <mailto:jd62 at zips.uakron.edu>
>
> _______________________________________________
> nengo-user mailing list
> nengo-user at ctnsrv.uwaterloo.ca
> http://ctnsrv.uwaterloo.ca/mailman/listinfo/nengo-user