NEURONAL DYNAMICS I:ACTIVATIONS AND SIGNALS SIGNAL MONOTONICITY An important exception:bell-shaped signal function or Gaussian signal functions S(x)=e-cx c>0 S=-2cxe S S"o∝-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. 66 SIGNAL MONOTONICITY An important exception: bell-shaped signal function or Gaussian signal functions 0 2 =  − S x e c cx ( ) 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. NEURONAL DYNAMICS Ⅰ: ACTIVATIONS AND SIGNALS