Network Motif Enrichment

Gene regulatory networks contain recurring subgraph patterns (motifs) that appear far more than in random networks. The feedforward loop, bifan, and SCC are enriched because they perform specific computational functions: sign-sensitive delay, multi-input integration, and bistability.

N nodes 14

Edge prob p 0.25

Randomizations 50

Z-score: Z = (N_real - ⟨N_rand⟩) / σ_rand | Significance threshold |Z| > 2 (p < 0.05).
Feedforward loop (FFL): A→B, A→C, B→C — sign-sensitive delay, pulse generator.
Bi-fan: A→C, A→D, B→C, B→D — allows combinatorial regulation.