The Cyclic Reaction network module with highly diffusible elements. The response of the module to a (A,B) gradient signal and a (C,D) localized signal is shown when X1 is highly diffusible and when X3 is highly diffusible. Note that the profiles of X2, X3 and X4 are coincident for the parameters chosen. (A,C) If only X1 is highly diffusible, then X1(dashed line) is spatially homogenous and the remaining species (solid line) have a stronger spatial variation (than the corresponding non-diffusible case). (B,D) If only X3 is highly diffusible then X2, X3 and X4(solid line) are spatially homogenous and X1(dashed line) assumes a profile qualitatively opposite to that of the signal with stronger spatial variation than the non-diffusible case.