leaky integrator

Rogene Eichler eichler at PI18.ARC.UMN.EDU
Fri May 21 18:25:19 EST 1993

> Articles by Softky & Koch, 93, and Levine, 91, (and many more) describe  
> modeling of neurons by a "leaky integrator", or "integrate and fire model".   
> These are essentially capacitive models of neurons, but they all seem to  
> include "reset"; after the neuron fires, its input (voltage) is set back to 0  
> (or resting potential).
> My question is:  to what extent is this "reset" biologically plausible?  It  
> seems to me that such a reset is very different from a refractory period.   

The "reset" that you refer to is the result of potassium channels being
opened. Since the nernst potential of potassium in neurons is below the
normal resting potential, the effect is to drive the membrane potential
to the resting value or below. This effect is accentuated by the inactivation
of the sodium channels, which provide the "fire" portion of the oscillation.

You are correct to suggest that the reset is different from a refractory
period. This refractory period can be thought of as the time period
required for the inactivation of the sodium inactivation gates. 


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