Fig. 3: GABAergic neuronal development in the isocortex.

a,b Representative STPT images of Gad2 cells in the a primary somatosensory cortex (SSp) and b primary auditory cortex (AUDp). c Temporal trajectory of Gad2 cell count vs. volume (mm³) in the isocortex. All data are reported as mean ± s.d. (includes shaded area between error bars). d Averaged Gad2 cell density patterns across isocortical areas. Each isocortical brain region falls into one of five categories, grouped by their previously known functional and anatomical connectivity profiles. e (left) Bayesian multilevel modeling, with a global hypothesis test and post hoc pairwise comparisons, was used to examine significant magnitude differences in density of Gad2 cells between all age pairs across isocortical regions (null, 0; ns, non-significant; significant). See Supplementary Data 1 for Estimates and Highest Posterior Density (HPD) intervals. (right) Functional data analysis (FDA) to examine significant differences between density patterns of isocortical Gad2 cells between all age pairs (null, 0; ns, non-significant; two-tailed Student’s t-test: *p < 0.05; **p < 0.005, ***p < 0.001, ****p < 0.0001). See Supplementary Data 1 for exact p-values. f Isocortical flatmap with Allen CCFv3 anatomical regions and border lines. The y-axis represents the bregma’s anterior-posterior (AP) coordinates, while the x-axis indicates azimuth coordinates to combine medial-lateral and dorsal-ventral direction. g Isocortical flatmaps of 3D counted and averaged Gad2 cell densities. h Confocal image of a cropped primary somatosensory region after fluorescence in situ hybridization, demonstrating colocalization of Gad2 (green), tdTomato (magenta), and DAPI (blue). i Quantification of individual and colocalized Gad2-positive and tdTomato-positive cells at P4 and P10 (total n = 8 mice, n = 4 mouse brain sections per age). P-values (p = 0.0159 for Gad2-positive cells between P4 and P10; p = 0.0180 for tdTomato-positive cells between P4 and P10) were obtained using a two-tailed Student’s t-test. All data are reported as mean ± s.d. (including the error bars). See Source Data for Gad2 cell counts, density, volume measurements, and abbreviations, all of which are provided as a Source Data file.