Optogenetics is a technique for controlling subpopulations of neurons in the 
intact brain using light. This technique has the potential to enhance basic 
systems neuroscience research and to inform the mechanisms and treatment of 
brain injury and disease. Before launching large-scale primate studies, the 
method needs to be further characterized and adapted for use in the primate 
brain. We assessed the safety and efficiency of two viral vector systems 
(lentivirus and adeno-associated virus), two human promoters (human synapsin 
(hSyn) and human thymocyte-1 (hThy-1)) and three excitatory and inhibitory 
mammalian codon-optimized opsins (channelrhodopsin-2, enhanced Natronomonas 
pharaonis halorhodopsin and the step-function opsin), which we characterized 
electrophysiologically, histologically and behaviorally in rhesus monkeys 
(Macaca mulatta). We also introduced a new device for measuring in vivo 
fluorescence over time, allowing minimally invasive assessment of construct 
expression in the intact brain. We present a set of optogenetic tools designed 
for optogenetic experiments in the non-human primate brain.