Differences in gene expression patterns are thought to be drivers of evolutionary changes in brain organization and function. Sousa et al. compared the transcriptomes of 16 brain regions in humans, chimpanzees and macaque monkeys, revealing brain-wide, regional and cell type-specific differences in gene expression between species, and identifying a population of tyrosine hydroxylase-expressing interneurons that are enriched in the human striatum and neocortex. These patterns of gene expression may underlie some of the behavioural and cognitive differences between species, as well as the human-specific vulnerability to some diseases.