# Command: testsuite::test_iaf_fudge

NEST HelpDesk | Command Index | NEST Quick Reference

Name:

    testsuite::test_iaf_fudge - sli script to test normalization of PSP for iaf_neuron model

Synopsis:

    (test_iaf_fudge) run -> compares response to spike input step with reference data

Description:

      The peak time of the postsynaptic potential (PSP) is calculated using
      the LambertW function. The theoretical peak voltage amplitude for a
      postsynaptic current of amplitude 1pA is then used to adjust the
      synaptic weight such that a PSP of amplitude 1mV is generated.  The
      success of this approach is verified by comparing the theoretical
      value with the result of a simulation where a single spike is sent to
      the neuron.

      The name of this test script has a historical explanation. Prior to
      July 2009 the analytical expression for the peak time of the PSP was
      not known to the NEST developers. Therefore the normalization factor
      required to adjust the PSP amplitude was computed by root finding
      outside of NEST. The factor was called "fudge" in examples and
      application code. The root finding was not done in NEST because infix
      mathematical notation only become available in SLI in January
      2009. The name "fudge" indicated that the origin of this value was not
      obvious from the simulation scripts and usage was inherently dangerous
      because a change of the time constants of the neuron model would
      invalidate the value of "fudge".

      Author:  July 2009, Helias

SeeAlso:

- iaf_neuron
- testsuite::test_iaf
- testsuite::test_lambertw
- LambertWm1

Source:

    /opt/conda/conda-bld/nest_1524088722951/work/nest-2.14.0/testsuite/unittests/test_iaf_fudge.sli

NEST HelpDesk | Command Index | NEST Quick Reference

© 2004 The NEST Initiative