Emergent and robust oscillations in a connectome-constrained spiking model of the Drosophila nerve cord: walking, courtship song, and half-center alternation survive local ablations

Central pattern generators (CPGs) are the canonical example of circuit-level rhythm generation, yet whether connectome-constrained spiking models can produce them - and how fragile such rhythms are - remains untested. In the MaleCNS connectome (the only Drosophila connectome with both brain and ventral nerve cord in one volume), we ignite three classes of oscillators from static synaptic weights. (1) A walking CPG: the Pugliese E1-E2-I1 motif oscillates on 6/6 seeds (58 cycles per 4 s; frequency scales with tonic drive, 6.9 to 15.4 Hz). (2) A courtship-song rhythm at 36-37 Hz (3/3 seeds), requiring post-inhibitory rebound and tunable by the adaptation time constant (53.5 to 34.5 Hz). (3) A half-center alternation - achieved here for the first time in a connectome spiking model - after host-side symmetrization of the inhibitory loop plus spike-frequency adaptation (envelope anti-correlation -0.45 to -0.86, 3/3 seeds). Gap-junction transmission closes the giant-fiber pathway to 0.1 ms (from 11-12 ms chemical). Pre-registered ablations then probe fragility: the walking rhythm survives silencing of the named inhibitory neuron I1 (and is strengthened, 14.97 to 23.53 rhythm score), of I2, of adaptation, and of I1+I2+SFA together (4,454 edges removed) - negative feedback is distributed across the VNC network rather than localized in the named motif, a direct correction to over-strong mechanistic claims. Project channel: «Правила игры» — https://t.me/law_of_the_game