The effect of diffusible species in the response of the negative feedback oscillator. The response is shown when the feedback element is highly diffusible (solid line) for a (A) gradient signal and (B,C) localized signal input. (A,B) A smooth concentration profile qualitatively similar to the signal is observed. This is because the diffusion of the feedback element acts to couple the different regions of the domain resulting in such a profile. (C) The temporal profile of the response is shown when Y is highly diffusible (dashed line) and non-diffusible (solid line), corresponding to the signal in (B). For the non-diffusible case oscillations are observed in the middle of the domain. However when Y is highly diffusible periodic oscillations are not observed in this region because the spatial average of the signal is not in the oscillatory regime. Thus, an heterogeneous, static profile emerges in the diffusible case.