Cellular specialization is central to the function of the mammalian brain. At the coarsest level, cells of different classes (for example, neurons, astrocytes, and endothelial cells) interact to maintain homeostasis and enable electrochemical communication. At finer levels, subtle specializations – such as those that distinguish neuron subtypes in the same region – can control behaviors such as appetite (Andermann and Lowell, 2017; Sternson, 2013), sex drive (Anderson, 2012), habit formation (O’Hare et al., 2016; Wang et al., 2011), spatial mapping (Moser et al., 2008), and associative learning (Krabbe et al., 2017). Some cell populations have been characterized in detail; many remain uncharacterized or have yet to be discovered.
