Configuring NetStim with Background Activity and Stimulus Input

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Krishna Chaitanya
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Location: University of Pavia

Configuring NetStim with Background Activity and Stimulus Input

Post by Krishna Chaitanya » Tue Sep 25, 2018 11:36 am

Hi,

I have been trying to configure NetStim to fire background noise (poissonian) along with stimulus specific activity from 300 to 350 ms. The background activity frequency is 1 Hz and I want to do it for 100 NetStims.

I have tried the noise parameter in NetStim but I couldn't get both background and stimulus specific activities in NetStims.

My problem: I want to configure network where I provide NetStims as input source which should have background activity and stimulus activity (two different frequencies).

Please note that my target neurons are point neurons, not biophysical models.

Kindly let me know how can I solve this. Thank you.

ted
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Re: Configuring NetStim with Background Activity and Stimulus Input

Post by ted » Tue Sep 25, 2018 7:42 pm

Tell me if I understand correctly:
You want to generate 100 event streams. Each event stream will contain "background" events that occur at times governed by the negative exponential distribution at a mean rate of 1 Hz. It will also contain events that happen at times of your choosing.

Krishna Chaitanya
Posts: 67
Joined: Wed Jan 18, 2012 12:25 am
Location: University of Pavia

Re: Configuring NetStim with Background Activity and Stimulus Input

Post by Krishna Chaitanya » Wed Sep 26, 2018 12:42 am

Hi Ted,

Yes, exactly.

ted
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Re: Configuring NetStim with Background Activity and Stimulus Input

Post by ted » Fri Sep 28, 2018 12:42 pm

If the NetStim targets can handle events from multiple NetStims (examples include all of NEURON's built-in synaptic mechanisms and artificial spiking cells, but many other implementations exist that are equally capable), then you could use a pair of NetStims to implement each afferent stream. One of the NetStims would generate the background activity and the other would be responsible for events that occur at times of your choosing. If the latter are precalculated times with statistics that a NetStim cannot generate, then you'll want to use a VecStim. For source code and an example of usage of VecStim, get NEURON's gzipped tar file source code, expand it, and see nrn/share/nrn/examples/nrniv/netcon/vecevent*.

A potential weakness of using two NetStims to emulate a single afferent spike stream is the possibility that a pair of events may be separated by an unrealistically short interval. That is easily prevented by having the two NetStims drive (with weight = 2) an IntFire1 that has its refrac parameter set to the minimum ISI that you want to allow, and its tau parameter set to a very small value (e.g. 1e-6). Then the IntFire1's output will be an event stream that combines background events and your chosen event times.

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