pseudotime neurons, whereas SST expression was highest in late (e.g. more mature) pseudotime neurons (Figure 3B, right panels). To verify these results, we compared gene expression changes correlated with pseudotime for our in vitro cells to gene expression patterns observed in the developing non-human primate and human brains (Figure S6)(Bakken et al., 2016). We find that genes positively or negatively correlated with pseudotime in vitro are expressed in similar patterns in vivo. These results provide insight into the dynamics of shifting cell type populations emerging during interneuron development, and their underlying transcriptional changes.