Combining models

Jason Sherfey edited this page Dec 19, 2017 · 48 revisions

DynaSim makes it easy to combine two or more existing DynaSim models. For instance, if you created a cortical model and someone else created a thalamic model, it is easy to combine them into a larger, thalamocortical model by concatenating their specifications and adding connections between their populations or compartments. This tutorial demonstrates how that can be achieved in DynaSim. The procedure is the same whether cells have one or more compartments and whether networks have one or more populations. This page demonstrates using the dsCombineSpecifications function to concatenate the specifications and adding connections between them either manually or using the dsApplyModifications function.

Contents:

Procedure: load two specifications and connect one or more populations (or compartments) in one specification to populations (or compartments) in the other specification.

This procedure can be used to combine any two models (e.g., networks, multi-compartment cells, point neurons, or any other models). It can be repeated any number of times to combine additional models into a single specification of a larger model.

Start with any two specifications. For instance,

s1=dsCheckSpecification('RS.pop'); % load RS specification from default DynaSim library
s2=dsCheckSpecification('FS.pop'); % load FS specification from default DynaSim library

Note: dsCheckSpecification is used here to load a demo specification from the DynaSim library; it does not need to be used with user-defined specifications stored in the variables s1 and s2.

The point neurons, multi-compartment cells, networks, or whatever is specified in s1 and s2 can be combined into a new, larger model by concatenating their specifications and adding connections between populations or compartments specified in them.

Manually add connections

s=dsCombineSpecifications(s1,s2);                  % concatenate specifications
s.connections(1).direction='RS->FS';               % note: "RS" and "FS" are population names in "RS.pop" and "FS.pop"
s.connections(1).mechanism_list={'iAMPA','iNMDA'}; % tip: see DynaSim/models for a list of mechanisms in the DynaSim library (e.g., iAMPA.mech, iNMDA.mech)
s.connections(2).direction='FS->RS';
s.connections(2).mechanism_list={'iGABAa'};

vary={'FS->RS.iGABAa','gGABAa',[0 1]   % tip: enter "open iGABAa.mech" to see GABAa parameters
      'RS->FS.iAMPA' ,'gAMPA' ,[0 1]   % tip: enter "open iAMPA.mech" to see AMPA parameters
      'RS->FS.iNMDA' ,'gNMDA' ,[0 20]};% tip: enter "open iNMDA.mech" to see NMDA parameters
simulator_options={'vary',vary,'tspan',[0 1000],'solver','rk1','dt',.01,'verbose_flag',1};

data=dsSimulate(s,simulator_options{:}); % run simulation
dsPlot(data,'plot_type','waveform');     % plot results

Using dsApplyModifications to add connections

s=dsCombineSpecifications(s1,s2);                                       % concatenate specifications
s=dsApplyModifications(s,{'RS->FS','mechanism_list','+(iAMPA,iNMDA)'}); % add AMPA and NMDA synapses from RS to FS
s=dsApplyModifications(s,{'FS->RS','mechanism_list','+iGABAa'});        % add GABAa synapse from FS to RS
data=dsSimulate(s,simulator_options{:}); % run simulation
dsPlot(data,'plot_type','waveform');     % waveform plots
dsPlot(data,'plot_type','raster');       % raster plots

In the above examples, each specification contains a point neuron model. However, the same approach will work using any two specifications. For instance, if s1 specifies a thalamic model, and s2 specifies a cortical model, then a thalamo-cortical model can be created by following the same procedure, substituting the names of populations and choosing the desired connection mechanisms. For Method 1 (Manually adding connections), the index into the connections field will need to be incremented to introduce new elements if any connections (e.g., between populations or compartments) already exist in either s1 or s2.

For a more complex example using dsApplyModifications to connect two intra-laminar circuits with multi-compartment neurons into a larger, inter-laminar network model, see: https://github.com/jsherfey/PFC_models/blob/master/PFC_2layers.m

To construct a thalamo-cortical model, specifications from the following repositories could be similarly combined:

Tips for storing specifications to facilitate combination:

  • Store specification in MAT file. e.g.) Given MAT file thalamus.mat with DynaSim specification spec for a thalamic model: load('thalamus.mat'); s1=spec;. Note: Models saved using the DynaSim GUI will be stored in MAT files and can be used in a script with this method.
  • Create a function that defines and outputs the specification. e.g.) Given function get_thalamus.m that returns a DynaSim specification for a thalamic model: s1=get_thalamus. Given a second function get_cortex.m that specifies a cortical model, the two specifications can be concatenated using s=dsCombineSpecifications(get_thalamus,get_cortex) and connected manually or using dsApplyModifications as described above.

Other tips for working with predefined specifications using dsApplyModifications:

  • Rename populations to avoid duplicate names. e.g.)
    • s=dsApplyModifications(s,{'RS','name','CtxRS'});
  • Modify population size without indexing the specification. e.g.)
    • s=dsApplyModifications(s,{'RS','size',10});
  • Modify parameters without indexing the specification. e.g.)
    • s=dsApplyModifications(s,{'RS','Cm',1.2});
  • Remove mechanisms (e.g., remove the anomalous rectifier h-current from RS). e.g.)
    • s=dsApplyModifications(s,{'RS','mechanism_list','-iAR'});

Specifying connectivity matrices

Using connectivity matrices defined in script:

nRS=10; % # of RS cells
nFS=2;  % # of FS cells
netcon=rand(nFS,nRS)<.5; % this can be any matrix with dimensions [N_pre x N_post]
s=dsApplyModifications(s,{'RS','size',nRS}); % set size of RS population
s=dsApplyModifications(s,{'FS','size',nFS}); % set size of FS population
s=dsApplyModifications(s,{'FS->RS','netcon',netcon}); % set connectivity matrix "netcon" from FS to RS cells
data=dsSimulate(s,simulator_options{:}); % run simulation
dsPlot(data,'plot_type','raster');       % plot results

Using expressions that evaluate to the appropriate connectivity matrix:

s=dsApplyModifications(s,{'FS->RS','netcon','rand(Npre,Npost)<.5'}); % set connectivity matrix "netcon"
data=dsSimulate(s,simulator_options{:}); % run simulation
dsPlot(data,'plot_type','raster');       % plot results

Both approaches are demonstrated in this specification of the pyramidal-interneuron gamma-rhythmic network.

Tips for efficient connectivity matrices:

  • The fastest simulation with a custom connectivity matrix can be achieved by specifying the desired custom matrix within the connection mechanism *.mech file. This can be achieved in three ways:
    • Specify the connectivity using built-in Matlab functions in a single line in the mechanism file (e.g., netcon=rand(N_pre,N_post)<prob; prob=.5 in a custom connection mechanism myAMPA.mech)
    • Creating an external function (e.g., get_connectivity) that returns the desired connectivity matrix and using the output to define the connectivity matrix in the mechanism file (e.g., netcon=get_connectivity(N_pre,N_post) in myAMPA.mech)
    • Saving the matrix to a MAT file and using it to define connectivity in the mechanism file (e.g., netcon=getfield(load('my_connectivity.mat','netcon')) in myAMPA.mech). Note: the variable netcon can be given any other name in the custom myAMPA.mech file.
  • In some cases, using sparse matrices can be more efficient. Sparse matrices will be used if sparse_flag is set to 1 in the call to dsSimulate.

Combining predefined model objects

  • Predefined mechanisms are stored in *.mech files (e.g., mech1.mech, mech2.mech) and include linkers that make their functions and state variables available for use in other mechanism and population equations. They can be specified using spec.populations.equations='dX/dt=f(X,t); ...; {mech1,mech2,...}' or spec.populations.mechanism_list = {'mech1','mech2',...}. See the introduction to mechanisms and Using custom mechanisms for more details.
  • Predefined populations of point neurons are stored in *.pop files (e.g., popX.pop) and are standalone population models. They can be specified in spec.populations.equations (e.g., spec.populations.equations='popX') or directly simulated (e.g., dsPlot(dsSimulate('popX'))). See Using predefined populations for more details and examples.
  • Predefined networks and multicompartment neurons are stored using functions (in *.m files) (e.g., net1.m, net2.m) that return specification structures, which also specify standalone models. They can be used the same way specification structures s1 and s2 are used above. Examples: s=dsCombineSpecifications(net1,net2), dsPlot(dsSimulate(net1)), s1=dsApplyModifications(net1,{'object','key',value}).
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