Measuring & Inducing Neural Activity Using Extracellular Fields II: Current-source density

Measuring and inducing neural activity in neurons using extracellular fields provides great insight into neurons functions and how they process information. This paper will consider the problem of trying to selectively sense and induce activity in neurons within a network in a living organism, using a small array of electrodes placed some distance away. One way to approach this problem is to solve for current source density (CSD) using known local field potentials. This involves solving the electrostatic forward problem where we measure the local filed potentials or low frequency part of the extracellular recorded potential by applying an equally spaced linear array or laminar electrode into the cortex [1]. The standard CSD method, involving a discrete double derivate, is then compared to inverse CSD (iCSD), where the CSD is assumed to have cylindrical symmetry and be localized in infinitely thin discs.