PSD volumes showed no clear extra similarity within 495 two-contact CA3 boutons after axon control in five mice

We tested whether postsynaptic density (PSD) volumes were more similar within shared hippocampal boutons than a reference that kept axon identity. We used 495 two-contact CA3 boutons, 990 contacts and 159 axons from five mice in a published CA1 stratum radiatum table. The test gave each mouse equal weight. Exact within-axon reassignment expectations preserved every measured PSD size. Measured squared log2 differences were 5.81% below this reference, with conditional two-sided p=0.2284. The mean measured-minus-reference difference was -0.11513. Its five-mouse Student 95% interval was -0.40023 to +0.16997. The result did not show clear extra matching. All five fixed controls gave uncertain overall results. An exploratory reference that kept mouse and activity label but exchanged sizes between axons gave a 13.41% reduction. Under the separate assumption that contact gain is proportional to PSD volume, equal splitting of a known summed gain gave 32.58% mean total-relative absolute error. The mean fraction of boutons with a gain ratio above 2:1 was 43.50%. Square-root gains reduced these values to 17.79% and 14.26%. These are structural and conditional model results, not measured currents, synchrony, or learning effects. Five selected mice, missing measurements, and absent target-neuron identities limit scope. An independent source reader matched 55,822 cells. The package preserves code, source provenance, a full row audit, calculations, figures, and repeat instructions. Original source measurements remain external under their original terms.

hippocampus · connectome · multisynaptic bouton · PSD volume · axon identity · synaptic gain · conditional randomization