This book, Signal Processing for Neuroscientists, A Companion Volume: Advanced Topics, Nonlinear Techniques and Multi-Channel Analysis, delves into sophisticated methodologies within the field of signal processing as applied to neuroscience. It is a companion piece to an introductory text on the same subject, providing readers with a deeper understanding through advanced topics such as linear and nonlinear systems analysis, and multi-channel recordings. The content emphasizes practical implementations using MATLAB, making it accessible for hands-on learning. Additionally, it offers numerous references back to foundational concepts, ensuring that both experienced researchers and newcomers can benefit from its rich material. This edition is essential reading for those eager to explore the complexities of signal processing in neuroscience, especially as electrode fabrication has improved and measurement equipment has become more affordable, leading to multi-channel electrophysiological measurements becoming commonplace.