A count model with overlap and fixed cell totals found no clear choice selectivity effect in one mouse PPC graph

We tested whether choice similarity explains synapse count allocation after each source and target cell total is fixed in a selected mouse posterior parietal cortex (PPC) graph. The reference used independent Poisson counts with mean set by cell factors and measured axon-dendrite overlap. Conditioning removed the cell factors. The two panels had 197 excitatory-to-inhibitory pairs with 29 synapses and 550 inhibitory-to-excitatory pairs with 156 synapses. Exact enumeration of 6,324 feasible tables gave p = 0.714 for the first count test. Four sampled chains gave p = 0.514 for the second. Both Holm values were 1.0. Individual 95% model intervals for the rate multiplier per +0.1 choice similarity were 0.015 to 22.29 and 0.873 to 1.333. An added check retained a negative inhibitory-to-excitatory density contrast: recorded r = -0.224 versus conditional mean -0.041, with unadjusted p = 0.030 and Holm p = 0.090 across four added tests. Count allocation and connected-pair density test different aspects of wiring. The sparse first panel left large effects possible. Results concern one animal, selected recorded pairs, and the stated count model. The package preserves new code, source provenance, analysis tables, all conditional draws, exact probabilities, figures, checks and repeat instructions.

connectome · posterior parietal cortex · choice selectivity · opponent inhibition · conditional inference · synapse count · axon-dendrite overlap