This unique volume presents a fruitful and beautiful mathematical world hidden in Caianiello's neuronic equations, which describe the instantaneous behavior of a model of a brain or thinking machine. The detailed analysis from a viewpoint of "dynamical systems", even in a single neuron case, enables us to obtain amazingly good rational approximations to the Hecke-Mahler series with two variables. Some interesting numerical applications of our rational approximations are also discussed. This book is fundamentally self-contained and many topics required in it are explained from the beginning. Each chapter contains a number of instructive and mostly original exercises at various levels.