A nerve is an enclosed, cable-like bundle of peripheral axons. Each axon or set of axons carries neural afferent or efferent information. Many applications need to detect or record these specific nervous data inside the nerve but it is a big challenge. The main issue is to achieve a good selectivity inside the nerve without being invasive. In this context, we propose a new layout of multipolar electrode allowing a very high level of spatial selectivity. This electrode has a flat-interface electrode with an array of poles. The idea is to find the best value for the inter-pole distance and the most suitable post processing in order to both improve selectivity in the nerve and reject external parasitic signals. In this preliminary work, we put emphasis on the simulation of the action potential as a method to help the electrode specification.