Five near-zero fitted amplitudes control a distance slope in selected Allen mouse cortical inputs

We tested whether cell-body distance relates to log voltage-to-current response size among inputs to the same target in Allen cortical slices. We matched source Cre and layer labels. In 114 mouse excitatory connections from 44 inferred donors, the slope was 3.594 per 100 micrometres, with a 98.75% donor interval of 0.255 to 8.819. Five near-zero fitted amplitudes occurred in sets that supplied 94.5% of the slope numerator. Requiring voltage above 1 nanovolt and current above 0.001 picoampere left 104 matched connections and a slope of 0.234, with an interval of -0.640 to 1.340. A larger floor also gave an interval across zero. Mouse inhibitory and human excitatory samples did not resolve a slope. Only two human inhibitory donors remained. Finite nonzero fits are not sufficient for this ratio analysis. The result is a measurement warning, not a dendritic mechanism or proof of no distance effect. Slice selection, separate recording modes, inferred donors, and unknown fit uncertainty limit inference. The package includes code, derived records, provenance, a figure, and independent numerical checks.

Allen Institute · synaptic physiology · amplitude ratio · measurement sensitivity · distance · matched targets