Since in a typical simulation the firing rate of the neurons is about
30Hz and the time constant of a synaptic current is typically about
3ms most of the time a synapse is ``idle''. This observation
encouraged us to implement some ideas of event driven simulators like
SpikeNet:
We decided to cut off the very far tail of the exponential decaying
synaptic responses (after 5 time constants) and remove those synapses
from the list of active synapses (which are advanced every time step).
A synapse is re-activated if it receives a further spike. For large
networks with lots of synapses these idea results in an average
speed-up of 2 to 3.
