testsuite::test_iaf_fudge - li script to test normalization of PSP for iaf_psc_alpha model
(test_iaf_fudge) run -> compares response to spike input step with reference data
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".
July 2009, Helias
/var/www/debian/nest/nest-simulator-2.20.0/testsuite/unittests/test_iaf_fudge.sli