To reveal neurons containing the calcium-binding protein calbindin, we used the CB38a anti-calbindin rabbit polyclonal antibody from Swant (CB38a, Swant; RRID AB_10000340) at a dilution of 1:10000. The pattern of immunoreactivity throughout the gibbon brain was similar to that seen in other mammals (e.g. Bhagwandin et al., 2013 (link); Bunce, Zikopoulos, Feinberg, & Barbas, 2013 (link); Gritti et al., 2003 (link)).