Positioning a stimulating electrode in close proximity to the target tissue insures a stable response to electrical stimulation and minimizes the amount of current that has to be injected. Cuff type electrodes have been used since the early days of the neural stimulation field and users were aware that the cuff could cause damage to the nerve. Here I show you a rigid cylinder electrode, a type used extensively in the 1960’s and 70’s. For safety considerations, it was generally accepted that the internal diameter of the cuff had to be larger than the target nerve. AAMI, the Association for the Advancement of Medical Instrumentation, produced a standard for cuff electrodes, the internal diameter of a cuff type electrode had to be 150% of the target nerve. Likely, not knowing the exact size of the nerve prior to implantation, most people preferred to error on the too large side. Shown here is cross section of tissue retrieved by a colleague from an experimental animal where the electrode, like the one shown here, had been implanted something like a month or so. Here is the target nerve and and the surrounding connective tissue. Take note, all unfilled space was filled with connective tissue and connective tissue will act as a scattering barrier to applied currents. The take-home message here is that any space will become occupied by connective tissues, therefore the internal diameter of the cuff needs to be close to the diameter of the nerve.