Signal Propagation Properties in the Drosophila melanogaster Connectome: Intermodal Isolation, Differential Motor Access, and Non-Trivial Temporal Amplification

Using the complete FlyWire v783 connectome ($N=138,639$ neurons; $E=15,091,983$ synapses), four parameter-free neural models, and two null-model families (Maslov-Sneppen, $N=100$; community-preserving, $N=5-10$), we characterize three signal propagation properties of the Drosophila melanogaster brain. (1) Active Intermodal Isolation. The topology separates sensory signals via directed inhibition (contralateral cancellation $=1.37$). During stimulus, separation is largely explained by generic modular structure ; post-stimulus amplification requires specific wiring (ZCP=+14.8σ). (2) Differential Motor Access by Concentration. Somatosensory neurons exhibit privileged motor access (Δ=+0.365, pₚₑᵣₘ<0.01). Canonical gustatory neurons alone produce significant privilege (Z=+4.5σ), although the effect is dominated by mechanosensory neurons (95.2%). Density analysis reveals that 7/10 sensory classes have motor access inferior to density expectation: the topology concentrates connections onto the somatosensory pathway rather than adding them. (3) Non-Trivial Temporal Amplification. Under graded dynamics, RDI rises from 0.63 to 0.83 post-stimulus, an effect that survives the community-preserving control (ZCP=+14.8σ), confirming dependence on fine wiring—including reciprocity (36x over density expectation). The parameter τ=0.119 corresponds to τₘ≈8.4 ms, center of the Drosophila physiological range.