Interneurons that Co-Express Parvalbumin and Calbindin

Humans evolved co-expression of calbindin and parvalbumin in cortical interneurons. The calcium-binding proteins calbindin D28K (CB) and parvalbumin (PV) are expressed by many interneurons in the cerebral cortex of mammals that have been studied. In the most commonly studied taxa, rodents and nonhuman primates, CB and PV are expressed by different, non-overlapping classes interneurons. In humans, however, it has been reported that human temporal cortex contains a population of interneurons that co-express CB and PV (del Rio and DeFelipe, 1997). This could represent a human specialization, but given the lack of information about other, nonhuman ape species, it is not possible to exclude the possibility that this is a hominid or hominoid specialization.