Subjects and task
Two male monkeys (Macaca mulatta) were prepared for neurophysiological experiments as described in detail elsewhere28. Monkeys were head restrained and seated in front of a 60 cm 60 cm tangent screen that subtended roughly 90° 90° of visual angle at the viewing distance of 32 cm. The display screen and stereoscopic projector (Christie Digital Mirage 2000) were mounted on a motion platform with six degrees of freedom (6DOF2000E; MOOG) that allowed us to translate the animal along any direction in the frontoparallel plane (fore–aft movements were not used here).
(excerpt from Nature http://www.nature.com/nature/journal/v452/n7187/full/nature06814.html)