**4. The nature and purpose of the book**

Revising the story of brain-behavior relationship research since its beginning, a treasure of information about how the brain works seems to have been discovered. Nevertheless, neuroscientists' research will continue until no more questions can arise [7]. Indeed, the benefits of the correlation-somatic-behavioral research approach [6] are greatly enhanced by the combined use of new technologies: neuroimaging, ICT-IoT assessment methods, and machine learning. It can be assumed that computerized functional localization is now a reality and that the brain-behavior relationship has already moved on to the next stage of its development (what we have just named the third level of brain functions). Considering the above, this volume aims at providing an overview of behavioral neuroscience and deepening neuronal mechanisms and brain circuits that regulate the fundamental aspects of human behavior, such as cognitive and emotional functions. It is intended to give the reader with the most up-to-date vision on how the interaction between biological mechanisms and neuropsychological processes leads to complex and highly organized behaviors. The approach is multidisciplinary, and various levels of investigation are represented.

*Behavioral Neuroscience*
