Is it possible to associate multiple gids with the same segment?

General issues of interest both for network and
individual cell parallelization.

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Is it possible to associate multiple gids with the same segment?

Post by JustasB »

I'm working with dendro-dendritic synapses where my pre- cell can have multiple pre-synaptic locations. Depending on section nseg, nearby pre- section(x) locations might be referring to the same segment. When I try to associate multiple gids with a given pre- segment, on the post- end only the synapses that receive events from the last associated gid receive it.

For example:

Code: Select all

presection.nseg = 3
ParallelContext.cell(gid1, NetCon(presection(0))     --> pc.gid_connect(gid1, PostSyn1) --> OK
ParallelContext.cell(gid2, NetCon(presection(0.49))  --> pc.gid_connect(gid2, PostSyn2) --> SILENT
ParallelContext.cell(gid3, NetCon(presection(0.5))   --> pc.gid_connect(gid3, PostSyn3) --> SILENT
ParallelContext.cell(gid4, NetCon(presection(0.51))  --> pc.gid_connect(gid4, PostSyn4) --> OK
ParallelContext.cell(gid5, NetCon(presection(1))     --> pc.gid_connect(gid5, PostSyn5) --> OK
In single process mode, multiple NetCons connected to the same segment do deliver events, e.g:

Code: Select all

presection.nseg = 3
NetCon(presection(0),      PostSyn1) --> OK
NetCon(presection(0.49),   PostSyn2) --> OK
NetCon(presection(0.5),    PostSyn3) --> OK
NetCon(presection(0.51),   PostSyn4) --> OK
NetCon(presection(1),      PostSyn5) --> OK
If multiple gids per segment are not allowed, I am not sure of what would be the best way for the post- rank to know the correct pre- gid.

Instantiating the pre-cell on the post- rank and then checking whether any of the pre- locations resolve to duplicate segments seems like one, rather inefficient way to do it. Is there a better way?

Tips and advice much appreciated.
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Re: Is it possible to associate multiple gids with the same segment?

Post by ted »

Yes, but why bother? Assuming that your conceptual model of spike-triggered synaptic transmission is

* transmission is triggered when a presynaptic variable crosses a user-specified threshold
* the presynaptic variable is the same for all postsynaptic targets of axons that arise from the presynaptic segment
* the presynaptic threshold for spike detection is the same for each of those axons

then the presynaptic segment needs only a single gid.
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