Human astrocytes are larger and more complex than those of rodents; human cortical astrocytes can exhibit over triple the diameter, and 10-fold the number of terminal processes, as rodent astrocytes (Oberheim et al. 2006; Oberheim et al. 2009). Even more intriguing, human astrocytes have both structural features and functional competencies unique to hominids, and exhibit a range of astrocytic pleomorphism without precedent in infraprimate mammals. On that basis, we have postulated that the functional roles of glia have expanded during evolution, and especially so with the appearance of hominids (Oberheim et al. 2006; Oberheim et al. 2009). These evolutionary changes are of particular interest because astrocytes have been shown to play vital roles in information processing within the CNS (Araque et al. 1999; Kang et al. 1998). Astrocytes are required for synaptogenesis and maintenance of synaptic density (Ullian et al. 2001), and a number of specific astrocytic modulators of synaptic plasticity have been identified, including the glypicans (Allen et al. 2012) and TNFα (Stellwagen and Malenka 2006), among others. Importantly, these ligands may be differentially expressed by human astroglia, potentially
