Axon-to-axon and axon-to-dendrite edges shared more directed pairs than sampled graphs with fixed partner counts by cell class in one larval fly brain

We tested whether the same directed neuron pairs connect through axon-to-axon (AA) and axon-to-dendrite (AD) edges. We used the released matrices from one first-instar fly larva. The main scope had 2,606 neurons with cell class labels. We kept AD fixed. Each primary control kept every neuron's AA input and output partner counts within each cell class. The map had 2,733 pairs with both edge types, or 8.24% of AA edges. The control mean was 1,231.31 pairs. The central 95% control range was 1,176 to 1,288. The observed count was 2.22 times the control mean. No saved primary draw reached it in 1,600 draws. A global-rate reference gave only 249.40 expected pairs. Adding neuron side to the class control gave a mean of 1,528.69, so the observed count was 1.79 times that mean. Higher count thresholds, an input fraction threshold, all matrix neurons, and removal of neurons with the LN label kept an excess. Thus the tested partner counts did not account for the recorded overlap. This is a graph result in one animal. It does not establish functional coupling or a biological cause. Physical contact, synapse weights, and annotation effects remain outside the controls. The package has code, source hashes, all score draws, figures, small graph checks, and repeat steps. The ten mirrored source CSV files match the primary record byte for byte.

Drosophila larva · connectome · axon-to-axon · axon-to-dendrite · multilayer network · edge overlap · fixed degrees · cell classes · graph controls · reproducible research