Presynaptic receptive-field offsets show no robust co-axial or motion-axis wiring rule beyond axon-dendrite proximity in the MICrONS mouse (2,600-3,090 connections)

Question: small tracing studies of mouse V1 layer 2/3 report that presynaptic partners lie along an axis set by the postsynaptic preferred orientation in visual space (Iacaruso 2017: collinear; Rossi 2020: elongated on the direction axis; Weiler 2022). We tested this rule in the MICrONS functional connectome (one mouse; Ding et al. 2025 tables). Approach: for each pair we measured the angle between the presynaptic receptive-field (RF) offset and the postsynaptic preferred edge axis. We compared EM-confirmed connections with unconnected axon-dendrite-proximity (ADP) and same-region controls. We used a conditional logit stratified by postsynaptic neuron with an RF-distance spline. RF offsets came from a soma-position retinotopic map (as in Rossi 2020), from digital-twin RFs, and from in-vivo STAs. We verified from the stimulus pixels that Monet2 motion is perpendicular to the stripes, so the edge axis is the preferred orientation + 90 deg. Main finding: with map offsets and ADP controls (2,600 connections, 1,646 postsynaptic neurons), the cos(2 psi) log-odds coefficient was 0.030 (95% CI -0.035 to 0.095). Thus the edge-to-motion-axis density ratio is 0.93-1.21. Digital-twin RFs gave 0.015 (-0.041 to 0.071). STA RFs gave a small collinear bias, 0.073 (0.017 to 0.129), which was not significant with in-vivo orientation, with a flipped y sign, or for V1 L2/3 targets. Whole ensembles against same-region controls showed weak collinear biases for two of three RF estimates. Proximity itself was almost isotropic (coefficients 0.009-0.024). No specification showed motion-axis elongation. Planted-rule simulations recovered beta = 0.1 in 92-95% of runs. Main limitations: one animal; orientation from noise stimuli; no direction preference in the released tables; V1 L2/3-only estimates are imprecise (density ratios 0.66-1.36 not excluded).

MICrONS · functional connectomics · mouse visual cortex · receptive field · orientation · collinear · association field · wiring rule · axon-dendrite proximity · conditional logistic regression · replication