Fig. 2: Polymodality and tuning among excitatory interneurons and projection neurons.

a Experimental design of imaging (top) and schematic of response thresholds (bottom). b Proportions of excitatory interneurons (IN, left) and SPB neurons (SPBN, right) that were responsive to cardinal modalities (cold, mechanical, heat). Shaded region represents the MHC polymodal population corresponding to c. c Percent of INs and SPBNs (averaged by animal) which displayed cardinal polymodality. *P < 0.05 (two-tailed unpaired t test, P = 0.0051). N = 6 animals for interneurons N = 3 animals for SPBNs. Data are presented as mean values ± SEM. d, Proportions of INs (left) and SBPNs (right) that were responsive to the mechanical sub-modalities: brush (purple), static low threshold (LT, blue), or static high threshold (HT, green). Pan-mechanical sensitivity (pan-mech) indicates responsiveness to all tested types of mechanical stimuli. Shaded region represents the MHC polymodal population corresponding to e. e Percent of INs and SPBNs (averaged by animal) which were pan-mechanical. *P < 0.05 (two-tailed unpaired t test, P = 0.0068). N = 4 animals for interneurons and N = 3 animals SPBNs. Data are presented as mean values ± SEM. f Schematic and examples of vector-based tuning. Top: ΔF/F Ca²⁺ traces evoked by brush (green), cold (blue), and heat (red). Bottom: modality response vectors (colored) and summed vectors indicating the final tuning (black). g, h Cardinal g and mechanical sub-modality h tuning of SDH interneurons grouped by their threshold-based categorization. SPBNs are shown separately. Black circle is 1 unit vector in diameter. N = 1265 cells for the cardinal modalities and 1080 cells for the mechanical sub-modalities from 5 mice including 22 SPB neurons and 6 mice for interneurons.