iaf_chs_2007 - Spike-response model used in Carandini et al 2007.
The membrane potential is the sum of stereotyped events: the postsynaptic
potentials (V_syn), waveforms that include a spike and the subsequent
after-hyperpolarization (V_spike) and Gaussian-distributed white noise.

The postsynaptic potential is described by alpha function where
U_epsp is the maximal amplitude of the EPSP and tau_epsp is the time to
peak of the EPSP.

The spike waveform is described as a delta peak followed by a membrane
potential reset and exponential decay. U_reset is the magnitude of the
reset/after-hyperpolarization and tau_reset is the time constant of
recovery from this hyperpolarization.

The linear subthresold dynamics is integrated by the Exact
Integration scheme [1]. The neuron dynamics is solved on the time
grid given by the computation step size. Incoming as well as emitted
spikes are forced to that grid.

The following parameters can be set in the status dictionary.

tau_epsp double - Membrane time constant in ms.
tau_reset double - Refractory time constant in ms.
U_epsp double - Maximum amplitude of the EPSP. Normalized.
U_reset double - Reset value of the membrane potential. Normalized.
U_noise double - Noise scale. Normalized.
noise vector- Noise signal.

SpikeEvent, DataLoggingRequest  


The way the noise term was implemented in the original model makes it
unsuitable for simulation in NEST. The workaround was to prepare the
noise signal externally prior to simulation. The noise signal,
if present, has to be at least as long as the simulation.

[1] Carandini M, Horton JC, Sincich LC (2007) Thalamic filtering of retinal
spike trains by postsynaptic summation. J Vis 7(14):20,1-11.
[2] Rotter S & Diesmann M (1999) Exact simulation of time-invariant linear
systems with applications to neuronal modeling. Biologial Cybernetics

Thomas Heiberg, Birgit Kriener 
May 2012