bug in synaptic mechanism

NMODL and the Channel Builder.
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Cal

bug in synaptic mechanism

Post by Cal »

Okay. Newer (but still sort of related to the original) question:

I've been running simulations using Netcon(s) to take a list of spike times and drive synapses onto a single compartment model. So far, so good.

Code: Select all

rf = new File()

for iii = 0,numinputs-1 {
	sprint(filename,"dumbfile%d.dat",iii+1)
	dumbfile = filename
	rf.ropen(dumbfile)

	rsp[iii] = new Vector()
	n = rsp[iii].scanf(rf)
	numspiking = rsp[iii].size()
	rf.close

	a[iii] = new IC_AMPA(0.5)
	a[iii].tau = ampatau
	nctemp1 = new NetCon(nil,a[iii],0,1,(ampaconduct/numinputs))
	//nctemp1 = new NetCon(nil,a[iii],0,1,(ampaconduct/2))
	nclist1.append(nctemp1)

	b[iii] = new IC_NMDA(0.5)
	nctemp2 = new NetCon(nil,b[iii],0,1,(nmdaconduct/numinputs))
	//nctemp2 = new NetCon(nil,b[iii],0,1,(nmdaconduct/2))
	nclist2.append(nctemp2)
}

proc loadspikes() { local jj
for jj=0,numinputs-1 {
	numss = rsp[jj].size()
	for ii=0,numss-1 {
		nclist1.o(jj).event((rsp[jj].x[ii] + delay))
		nclist2.o(jj).event((rsp[jj].x[ii] + delay))
}}}

fih = new FInitializeHandler("loadspikes()")
So this should be a sample of the relevant code. Once I run the model, I decided to graph the generated NMDA current. So, I graph "b[0].i".

Now, I expect that if I use spike times with low ISI - say for instance, 10ms, I would expect that the resulting NMDA current response would overlap, as the next incoming synaptic event would occur before the full decay of the previous evoked NMDA current (Summation of NMDA current).

However, what I get is this:
Image
and if I zoom in on a couple of the EPSCs:
Image

It appears that with each incoming EPSC, the previous one is truncated. Yikes. Any way to fix this?
ted
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Re: bug in synaptic mechanism

Post by ted »

The original topic was "Netcon source" and it was posted in the "Getting started" area
viewtopic.php?f=15&t=1778
which was a bit of a stretch, because it could just as easily have qualified for "Modeling networks". Your latest question really does open up a new area of inquiry, so I have moved it to "Adding new mechanisms and functions to NEURON".

Looks like your IC_AMPA mechanism has a bug. If you like, I'll be glad to look at it--send just the mod file, please, to
ted dot carnevale at yale dot edu
Cal

Re: bug in synaptic mechanism

Post by Cal »

Sent! I'll try and look over my code as well.
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