Two adult rhesus macaques (Table 1; one 13-year-old male and one 4.5-year-old female) were deeply anesthetized with intravenous injection of sodium pentobarbital (50 mg/kg i.v., Fatal-Plus, Vortech Pharmaceuticals, Dearborn, MI) and perfused transcardially with ice cold 1% paraformaldehyde in 0.1 M phosphate buffer (pH 7.4) for 2 minutes at a rate of 250 ml/min, followed by ice cold 4% paraformaldehyde in 0.1 M phosphate buffer (pH 7.4) for 10 minutes at a rate of 250 ml/minute, then continued for another 50 minutes at a rate of 100 ml/min. The monkey’s head was packed in ice for the entire duration of the perfusion. The brains were extracted immediately following perfusion and postfixed for 6 hours in the same fixative at 4°C under constant, gentle agitation. Brains were then immersed in a cryoprotective solution made of 10% glycerol and 2% dimethyl sulfoxide (DMSO; Fisher Scientific, Waltham, MA) in 0.1M phosphate buffer for 24 hours at 4°C, followed by 72 hours in 20% glycerol and 2% DMSO in 0.1 M phosphate buffer at 4°C. Finally, the brains were cut into three blocks in the coronal plane using a histological blade, then flash frozen in isopentane (2-methyl-butane, Fisher Scientific, Waltham, MA) cooled in a 100% ethanol dry ice bath. The blocks were then wrapped with aluminum foil and stored at −70°C until cutting.