In the present proposal I will describe a novel research agenda for understanding the neural basis of mammalian behavior. Three central problems prevent current research from explaining mammalian behavior in terms of neural mechanisms. First, there is a preponderance of correlative evidence in systems neuroscience. Second there is generally insufficient information about the individual neuron(s) under study. Third, there is a lack of integration of information. Current neuroscience is characterized by strongly diverging research interests and this highly divergent and specialized research program cannot lead to systemic understanding of brain function. We will confront these problems by three novel research approaches: (1) We will establish a causal link between cellular activity and behavior by a single-cell-stimulation / reverse physiology approach. (2) We will obtain rich information about single neurons by whole-cell recordings in awake behaving animals. (3) We will perform a whole-brain-analysis of a novel model organism, the Etruscan shrew, in which we will record the activity of all neurons in the shrew s brain. The research proposed here is unique, because as no other research group investigates brain function by a single-cell-stimulation, by intracellular recordings in freely moving animals, or by whole-brain analysis. The research outlined here will probe the relationship of neural activity and behavior in an entirely unprecedented fashion.