Synapse spacing gave no clear gain in a fixed ridge test of 271 calcium response means from 65 C. elegans worms

We tested whether the spacing of chemical synapses helps predict calcium response size after stimulation of one neuron. We joined adult C. elegans maps 7 and 8 to 317 event-target records from 65 other worms. The sample had 151 named directions and 271 animal-direction means. The spacing score compared actual path distances along the source neurite with distances from a proximal-location reference. A nested ridge test excluded complete animals from training. Controls included synapse count, geometry summaries, cell classes and response covariates. Adding spacing changed squared prediction error by -0.013%. A positive value means less error. The 95% animal resample range was -0.263% to +0.219%, with fitted predictions fixed. The adjusted rank correlation across directions was -0.009. Planned count and separate-map checks gave no clear gain. Response summaries repeated poorly across animals in 66 repeated directions. Added signals of known size could be detected. Three other animal splits gave gains from -0.157% to +3.027%, so the narrow main range is not a limit on other fitted models. An independent replay reproduced all 317 selected event rows from original NWB files. The result limits this response measure and fixed test. It does not show that synapse spacing has no effect on neural transmission. The package has code, input facts, source versions and hashes, all predictions, fitted states, figures and repeat instructions.

Caenorhabditis elegans · connectome · synapse spacing · signal propagation · calcium imaging · structure and function · animal exclusion · repeatability