ELECTRODE_CURRENT
is currently not recognized by modcc.
The documentation regarding this feature is sparse. It appears to be a direct injection of current in the cell. Not passing the cell membrane.
The NEURON book does have an entry, but does not describe anything about it.
The mention I found online:
intracellular stimulating electrode
An intracellular stimulating electrode is similar to a shunt in the sense that both are localized
sources of current that are modeled as point processes. However, the current from a stimulating
electrode is not generated by an opening in the cell membrane but instead is injected directly into
the cell. This particular model of a stimulating electrode has the additional difference that the
current changes discontinuously, i.e. it is a pulse with distinct start and stop times.
: Current clamp
NEURON {
POINT_PROCESS IClamp1
RANGE del, dur, amp, i
ELECTRODE_CURRENT i
}
UNITS { (nA) = (nanoamp) }
Figure 4
Hines and Carnevale: Expanding NEURON with NMODL
Revised 4/6/2000 Page 12
PARAMETER {
del (ms)
dur (ms) < 0, 1e9 >
amp (nA)
}
ASSIGNED { i (nA) }
INITIAL { i = 0 }
BREAKPOINT {
at_time(del)
at_time(del+dur)
if (t < del + dur && t > del) {
i = amp
} else {
i = 0
}
}
Listing 3. iclamp1.mod
The NEURON block
This mechanism is identical to the built-in IClamp model. Calling it IClamp1 allows the
reader to test and modify it without conflict with the existing IClamp point process.
This model of a current clamp generates a rectangular current pulse whose amplitude amp in
nanoamperes, start time del in milliseconds, and duration dur in milliseconds are all adjustable
by the user. Furthermore, these parameters are individually adjustable for each separate instance
of this mechanism. Therefore they are declared as RANGE variables in the NEURON block.
The current i delivered by IClamp1 is declared in the NEURON block to make it available for
examination. The ELECTRODE_CURRENT statement has two important consequences: positive
values of i will depolarize the cell (in contrast to the hyperpolarizing effect of positive
transmembrane currents), and when the extracellular mechanism is present there will be a
change in the extracellular potential vext. Further discussion of extracellular fields is beyond the
scope of this paper.