Network Motif: Feed-Forward Loop

Signal propagation through the coherent type-1 FFL — a sign-sensitive delay filter in gene regulatory networks

Threshold: 0.50 Y-delay: 8 steps Phase: -
About: The coherent type-1 feed-forward loop (C1-FFL) is the most common network motif in transcription networks. X activates Y and Z; Y also activates Z. This creates a sign-sensitive delay: Z responds to persistent ON signals (filtered noise) but turns off quickly. Z-score vs random networks is typically >10, making FFLs statistically over-represented. The three nodes and their connections illustrate how simple topology generates complex temporal dynamics.