A reversible system for chronic recordings in macaque monkeys.

We propose a system for head fixation and neuronal recording that minimizes surgery for implantation. Fixation is obtained by posts which are attached to the opposite sides of the skull and are connected by a rigid frame around the animal's head. As forces are counterbalanced and distributed around the head, the system does not need to be implanted into the skull, and thus allows for continuous adjustment to the growing skull in young animals. Except for small incisions for the posts, the skin over the skull is left intact. Recording is achieved through small bone holes which are easily reached by means of conical guide tubes. The system provides perfect stability of recording, allows flexible access to various areas of the brain and can be easily removed during longer pauses in experiments. The use of this system may also decrease the number of laboratory animals needed.