Figure 5. FCD systems with two internal layer components need not generally integrate multiple signals in a log-linear manner.

(A) A model where each input interacts with its own internal layer component. In cases where one pathway has fast dynamics and the second pathway has a delay, the response to fold change steps in input one and two can be temporally separated. (B) Response to a step in L₁ is a fast pulse. (C) Response to a step in L₂ is a delayed pulse. (D) Response to simultaneous steps of L₁ and L₂ gives a two-pulse shape, and is thus not equivalent to any step of a single ligand.