Feedforward Loop — Transcription Network Motif

The feedforward loop (FFL) is a 3-node motif where regulator X controls both Y and output Z, while Y also regulates Z. The coherent FFL (C1) acts as a sign-sensitive delay; the incoherent FFL (I1) generates pulses. These dynamics help cells filter noise and respond adaptively.

Motif Type

Signal duration (τ): 80 Y delay (K_Y): 0.30 Z production β: 1.20

Coherent FFL (C1): X activates both Y and Z; Y activates Z (AND gate). There is a delay on Z activation (Y must accumulate) but fast Z off when X turns off. Acts as a persistence filter — transient inputs are ignored.