Interneurons that Co-Express Parvalbumin and Calbindin

In fact, the greatest degree of calcium-binding protein colocalization in primates has been found in human temporal cortex, where 14% of PV-expressing interneurons also express CB (de Rio & DeFelipe, 1997). In most other areas, this overlap is quite minimal. The temporal cortex is involved in memory formation and consolidation among other things. So this greater degree of overlap in humans may have some functional relevance, contributing to human uniqueness. Other studies looking at macaques found that, in the basolateral amygdala, approximately 25% of PV-expressing interneurons also express CB (Mascagni et al., 2009). This brain area is involved in fear memory and emotional arousal. Studies looking at the developing visual cortex in macaques have found that most PV-expressing interneurons also co-express CB before birth yet lose this co-expression with development (Yan, Van Brederode, & Hendrickson, 1995). Further studies directly comparing humans and nonhuman primates are needed. Of course, histology experiments with humans are more difficult as post-mortem brains are required. Additionally, it is important to note that interneurons that express PV and CB are just a subpopulation of all the interneurons in the brain. Additionally, there are other genetic markers for interneurons that are not calcium-binding proteins, such as somatostatin and cholecystokinin, that may also be co-expressed with calcium-binding proteins and undoubtedly has some functional significance.