Fig. 6: Perisomatic feature space enables more efficient search for unique cells.

a, 2D UMAP embedding highlighting a chandelier cell (orange dot), a 5P-NP-targeting cell (blue dot) and their respective 20 nearest neighbours in the high-dimensional perisomatic feature space. Note, UMAP nonlinearly distorts feature space, so not all nearest neighbours appear closest in the plot. b, Example proofread chandelier cell in L2/3 (dendrite in black, axon in grey). Output synapses are marked along the axon and coloured by subclass prediction. Note the characteristic vertical chains of synapses onto 23P cells. c, Chandelier cells are characterized by their preference to synapse onto the AIS of target cells^34,35 (quantified here by measuring the angle between the target soma and the synapse (ϕ) and the distance from the soma (r)). d, Heat map illustrating the angle and distance distribution of the chandelier cell shown in b as well as two non-Chandelier inhibitory examples. Colour denotes the normalized synapse density for each cell. Synapses located at an angle >160° were considered onto the AIS of the target cell (shown by the dashed line). e, Angular distribution histogram of the chandelier cell (top row), 20 nearest neighbours in the perisomatic feature space, and 20 random inhibitory cells (P < 0.00001). f, Example cell that preferentially targets the rare 5P-NP subclass (dendrite in black, axon in grey); points represent target cell soma locations coloured by predicted subclass. Output synapse counts reflect strong preference to 5P-NP cells. For all box plots: centre line, median; box limits, upper and lower quartiles; whiskers, 1.5× interquartile range; outliers shown. g, Fraction of output connectivity onto neuronal subclasses of the 5P-NP-targeting cell (top row), 20 nearest neighbours in the perisomatic feature space, and 20 random inhibitory cells (P < 0.00001). All P values reported and asterisks represent significance by two-tailed Fisher exact test.