The extracellular potentials of single active fibre: Effects of finite fibre length

This paper presents a generalized forward model for studying the electrical field due to a finite active fibre in a finite volume conductor. The mathematical solutions of this problem are formulated and the effects of finite length on extracellular potential are discussed. Our simulations show that when the action potential (AP) has not reached the end of fibre, the infinite axon model is still suitable for spatial extracellular potential calculation even though the fibre length is limited: and while AP reaches fibre end the extracellular current flow will concentrate in the immediate vicinity of the end, and therefore produce the variance of extracellular potentials. This "concentration" effect is considered varying with the geometry of volume conductor.