**Name:**

testsuite::test_iaf_dc - sli script for test of iaf_psc_alpha with external DC current

**Synopsis:**

(test_iaf_dc) run -> compare cout with comments in file

**Description:**

test_iaf_dc.sli is a test of a specific feature of the iaf_psc_alpha

model. It is tested at which time and how an external DC current affects

the state of the neuron, the membrane potential in particular.

This is probably the simplest setup demonstrating how an external

continuous function (the DC) can be incorporated into a system with

point event interaction. A general introduction, including examples

not restricted to piecewise constant functions, can be found in [1].

The expected output is documented and briefly commented at the end of

the script.

Cleary, the result of this script is not resolution independent. The

choice of the computation step size determines at which point in time

the current affects the neuron.

There are 2 problems with this script:

1. A network element (here the DC generator) can only change its state

when it performs a computation (update) step t -> t + h.

Thus, the earliest possible time the DC generator can be switched on

is at t=h. This is the default. Therefore, the time of onset depends

on the computation step size.

2. The default delay between the DC generator and the neuron is the minimal

allowed value of 1 h. Therefore, the delay of the current depends on

the computation step size.

A sequence of further test scripts (SeeAlso key below) demonstrates and

verifies how the SLI script can be made independent of the computation

step size. This leads to properly aligned and identical voltage traces

for simulations carried out with different computation step sizes.

**References:**

[1] Rotter S & Diesmann M (1999) Exact simulation of time-invariant linear

systems with applications to neuronal modeling. Biologial Cybernetics

81:381-402.

Author: February 2004, Diesmann, Gewaltig, Plesser

**SeeAlso:**

- iaf_psc_alpha
- testsuite::test_iaf_dc_aligned
- testsuite::test_iaf_dc_aligned_delay
- testsuite::test_iaf_dc_aligned_stop

**Source:**

/home/graber/work-nest/nest-git/nest-simulator/testsuite/unittests/test_iaf_dc.sli