Coherent Feedforward Loop

Feedforward loops are the most abundant network motif in gene regulation networks (Shen-Orr et al., 2002). The C1-FFL with AND logic acts as a sign-sensitive delay: it delays activation response to brief input pulses (filtering noise) but responds immediately to sustained input. On signal removal, it shuts off quickly. The I1-FFL generates precise output pulses regardless of input level (adaptation). These motifs are "building blocks" of regulatory networks — evolution reuses them because they provide robust computational functions.