Spike Sorting

Excitable cells, such as neurons, produce action potentials (APs) that in extracel- lular recordings are often referred to as spikes. In these recordings, APs indeed appear as sharp spikes deviated from the noisy baseline. The contributions of each cell must be isolated from the background noise and from those of the other cells. The process of estimating one or more AP waveforms and their discharge instances (firing patterns) from multiunit recordings is known as spike sorting. Resolving overlapped APs is a major difficulty in automatic spike sorting methods. Therefore, this chapter is in large part dedicated to discussing this issue; we focus on state-of-the-art techniques addressing the problem of spike sorting, including the resolution of overlapped APs. In the section "Signal model", we propose the mathematical modeling of multiunit recordings and the complexity in the resolution of overlapped APs. Then, in section "State of the art," we sum- marize state-of-the-art spike sorting algorithms and discuss the advantages and limitations of each and the applicability of these methods for different types of experimental demands. The final section provides the conclusions