(a) Representative sections of neuronal input labeling to OPCs following stereotaxic injection of SADΔG-EGFP(EnvA) to corpus callosum underlying the secondary motor area. Green = EGFP, white = DAPI. (b) Schematic of injection site. (c) Linear regression fit of neuronal input/Pdgfra+ OPC starter cells. Each point represents one animal, n = 12 animals, R2 = 0.8732, slope = 23.46 ± 2.8 standard error. (d) Representative confocal micrograph of EGFP+ (green) input neurons in medial prefrontal (mPFC) cortex. (e) Inputs to callosal OPCs largely arise from frontal association cortices but also include primary motor and somatosensory areas and thalamic nuclei. Each bar represents mean input percentage, error bars indicate SEM, n = 10 total. mPFC = medial prefrontal cortex (anterior cingulate, prelimbic, infralimbic regions), MOs = secondary motor area, MOp = primary motor area, SSp = primary somatosensory area, TH = thalamus (including all thalamic nuclei). (f) Percent of input neurons ipsilateral or contralateral to the OPC starter cells. Bars indicate mean, error bars indicate SEM, n = 10 animals. (g) Representative image of parvalbumin+ (PV+, magenta) GFP+ (green) input neuron (arrowhead) and quantification of percentage of input neurons that co-label with immunofluorescence makers for PV, somatostatin (SOM), or vasoactive intestinal peptide (VIP). Bars represent mean, error bars indicate SEM, n = 6 animals total. Scale bars in (d,g) represent 20 microns.