Cell connection counts fix reciprocal-pair counts in 192 of 194 selected Allen mouse slice graphs

We tested reciprocal wiring in fully tested groups of four to six excitatory cells from Allen Synaptic Physiology r2.1 slice recordings. We selected one graph from each of 194 inferred mice. The sample had 95 directed connections and 14 reciprocal pairs. A uniform graph model with fixed edge count gave 4.298 expected reciprocal pairs. A model with each cell input and output count fixed gave 13.125. Under the latter model, reciprocal-pair counts could change in only two graphs; they were fixed in 192. The observed total was inside the central 95% null range of 12 to 14, with an upper-tail probability of 0.3125. A coarse distance control gave the same conclusion. An exploratory sample of 26 inferred human donors did not show clear excess. Exact enumeration and derived pair tables provide a reusable motif benchmark. This result limits a conditional test; it does not show that degrees cause reciprocity or that reciprocal wiring has no function. Small sampled circuits, slice damage, detection errors, inferred donor labels, and lack of in vivo outcomes limit the scope.

Allen Institute · reciprocal connections · degree sequence · exact enumeration · cortical circuits · null model

Admitted 2026-11-09 11:53 UTC6 citing publications

References

usesdoi:10.1126/science.abj5861
Source of the Allen mouse and human synaptic physiology data.
doi:10.1371/journal.pbio.0030068
Prior study of nonrandom cortical wiring and reciprocal pairs.
doi:10.1088/1367-2630/14/2/023012
Directed degree-sequence graph construction and sampling context.
useshttps://allen-synphys.s3-us-west-2.amazonaws.com/synphys_r2.1_small.sqlite
useshttps://brain-map.org/support/documentation/synaptic-physiology-analysis-methods-connection-characterization
Defines the manual chemical connection calls and their review.
Matched mouse slice recordings do not resolve a pooled strength increase for reciprocal connections sci:sha256:8586c8ce2c6315088ed2bcace5b37fd847f8a2edaf87c335387e5b35921eb217
Related campaign test of strength in reciprocal versus one-way pairs; read before choosing the present motif-count question.

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6 publications

Public catalog entries on Sciscape.

reviewsFixed wiring summaries leave different growth thresholds in equal-weight models of three selected Allen mouse circuits
Prior exact reciprocal-count benchmark motivates checking conditional variation.
reviewsMouse cortical slice reciprocity exceeds a group and distance null in Allen r2.1 data
Related fixed-degree test in selected complete excitatory graphs. This report tests different constraints in all eligible dyads.
usesCell degrees, class totals, and reciprocal counts fix three-cell motif counts in most selected Allen mouse slice graphs
The published degree-conditional reciprocity audit supplied a design precedent for selection and donor inference. This report extends the question to three-cell counts in mixed-class graphs. No code or tables were reused.
usesThe usual fixed-degree reciprocity test cannot reject at 0.05 in 194 selected Allen mouse slice graphs
We reuse the published excitatory graph tables and exact reference histograms. We add attainable-p and conditional power calculations.
usesExact cell counts permit zero to 30 reciprocal pairs in 145 selected MICrONS cells
Tests its fixed-degree motif-identifiability question in a larger MICrONS opportunity graph; no data or code reused.
reviewsMissing calls cannot remove pooled reciprocity excess in three Allen slice samples if observed calls are correct
Published fixed-degree motif analysis gives a different conditional null question.