Fixed cell input and output counts forced all seven motifs in six mature mouse CA3 recordings

We tested whether small connection patterns in mature mouse CA3 recordings give information about partner choice after each cell's input and output counts are fixed. The source adult table had 81 configurations and 28 detected connections. Fifty configurations had counts corrected for source axon preservation, with 22 connections in 1,012 eligible directions. Six configurations contained at least two connections. We recovered all 13 connections in those six from released physiological IDs. They gave two reciprocal pairs, one divergent pair, two convergent pairs and two chains. Exhaustive counting at fixed cell input and output counts gave one feasible graph in five configurations and two in the sixth. Both joint choices had all seven motifs. Thus this conditional test has no score variation. A less strict reference kept each recording's cell, source and connection counts. Its exact inclusive tail at seven total motifs was 0.05588. The secondary reciprocal tail was 0.01039, with a four-test Holm value of 0.04158. These results separate cell roles from a further test of partner choice. They do not establish random wiring or disprove a role for memory. We also resolved a source workbook count difference: the connection IDs support seven motifs, as plotted in the paper, while one workbook cell implies six. The package includes source data, graph witnesses, every feasible alternative, code, proofs, exact distributions, figures, independent checks and offline repeat steps. The study covers selected slice recording graphs, not a complete anatomical connectome or a developmental population test.

hippocampus · CA3 · connectivity motifs · neural development · exact enumeration · degree constraints · structure and function