Class CFPRF_ActivityBased

source code

                       object --+        
                                |        
param.parameterized.Parameterized --+    
                                    |    
                base.cf.CFPResponseFn --+
                                        |
                                       CFPRF_ActivityBased

Calculate the activity of each unit nonlinearly based on the input activity.

The activity is calculated from the input activity, the weights, and a strength that is a function of the input activity. This allows connections to have either an excitatory or inhibitory effect, depending on the activity entering the unit in question.

The strength function is a generalized logistic curve (Richards' curve), a flexible function for specifying a nonlinear growth curve:

y = l + ( u /(1 + b exp(-r (x - 2m)) ^ (1 / b)) )

This function has five parameters:

* l: the lower asymptote, i.e. the value at infinity;
* u: the upper asymptote minus l, i.e. (u + l) is the value at minus infinity;
* m: the time of maximum growth;
* r: the growth rate;
* b: affects near which asymptote maximum growth occurs.

Richards, F.J. 1959 A flexible growth function for empirical use. J. Experimental Botany 10: 290--300, 1959. http://en.wikipedia.org/wiki/Generalised_logistic_curve