SIGNAL MONOTONICITY In general,signal functions are monotone nondecreasing S'>=0.In practice this means signal functions have an upper bound or saturation value An important exception:bell-shaped signal function or Gaussian signal functions S(x)=e-r c>0 S=-2cxe S"oc-x The sign of the signal-activation derivation s'is opposite the sign of the activation x.We shall assume signal functions are monotone nondecreasing unless stated otherwise.SIGNAL MONOTONICITY ( ) 0 2 =  − S x e c cx • In general, signal functions are monotone nondecreasing S’>=0. In practice this means signal functions have an upper bound or saturation value. • An important exception: bell-shaped signal function or Gaussian signal functions S cxe S x cx = −  − − ' 2 , ' 2 The sign of the signal-activation derivation s’ is opposite the sign of the activation x. We shall assume signal functions are monotone nondecreasing unless stated otherwise