Chronic implantation of gas cryoprobes in monkeys brain stem.

Cooling probe sheaths can accurately be implanted adjacent to brain stem nuclei of fascicularis monkeys making it possible to cool target nuclei repeatedly in long-term behavioral experiments. A description is given of the construction and use of flexible probe sheaths for chronic implantation. Appropriate therapy is detailed to counteract brain edema after implantation. A gas cooling system is described for effective cooling beyond the sheath tip. Effective operation of this system is proven by the effects of cooling the inferior olive on complex spike activity in contralateral cerebellar cortex.