A minimally invasive and reversible system for chronic recordings from multiple brain sites in macaque monkeys

We have developed a reversible system for performing simultaneous recordings from multiple brain areas of trained macaque monkeys. It consists of a near-circular halo fitted around the head of the monkey with 5-10 thin plastic or stainless steel posts that either jut against or are screwed into the skull, respectively. Both methods of implantation of the posts are easily reversible, enabling protracted recordings over many years and training the monkeys in more complex tasks. The former is more useful for shorter periods of recordings (2-4 months) separated by long intervals and the latter for longer periods of recordings at a time (6-12 months). With both systems, essentially the entire scalp is intact, allowing multi-site recordings from a number of dorsal cortical areas, as well as other areas, simultaneously. These recordings are performed through tiny craniotomies of usually less than 2mm diameter, which are fitted with small plastic cones that serve as guide tubes for the microelectrodes. The surgery involved in these procedures is relatively minor compared to classical methods and the implants are also usually free of infections, thus requiring little maintenance of recording chambers.