Functional Electrical Stimulation (FES) is now a fast growing field including well established applications as well as pioneering work on futuristic prostheses. Among the recent clinical applications, Vagus nerve stimulation (VNS) seems very promising in the treatment of several conditions not the least being epilepsy. Despite this success, much of this method remains entirely empirical and surely needs more basic study.

Such studies require the recording of the action potentials and compound nerve potentials triggered by the vagal nerve stimulation. We have adapted the self sizing spiral cuff electrode in order to allow such studies to be done in chronic rat preparations despite the small space available. Basic questions can be explored such as exploring the optimal stimulation parameters, identifying the activated fiber diameter or checking the existence of an anodal block in one of the propagation directions. The newly designed cuff electrode has four internal contacts facing the nerve along its length (two central ones for stimulation and one on each extremity for recordings) and one contact facing outwards used as a reference. The internal contacts are placed in such an asymmetric position that one of the stimulating contacts is at equal distance of 4 mm from the two recording contacts. The other stimulation contact, located at 2 mm from the first one, is at 2 mm and 6 mm respectively from the recording contacts. The cuff length is 10 mm. The stimulation and recording platinum contacts can thus be implanted in a single spiral electrode made of biocompatible silicone rubber.