Neuron charging

[Gary Frank]

Hi all!

I am designing a computational neural network to do object recognition. 
 I am basing it as closely as possible on the brain.  I have been 
reading brain researcher David Hubel's book "Eye, Brain, and Vision" as 
a guide.  There is some information, important to the design of the ANN 
that I don't understand.  As I understand it, neurons fire at 
increasingly high rates as the conditions they were designed for are 
met.  I wonder if the post synaptic neurons that receive these impulses 
are "charged up" as a result.  In other words, if a neuron doesn't 
receive enough inputs at a single instant in time to cause it to fire 
right away, is it more likely to fire in the near future, upon receiving 
more inputs, because of the inputs it received a short time ago?  If so, 
how long does this "charge" last?

Many thanks in advance!
Gary Frank