The brain is acting through the interaction of billions of neurons and myriads of action potentials that are criss-crossing within and between brain areas. To make sense of this complexity, one must use mathematical tools and sophisticated analysis methods in order to extract the important information and create reduced models of brain function. Together, faculty members and students at the Weizmann Institute, coming from diverse quantitative backgrounds such as physics, engineering, mathematics and computer science, are breaking new cutting-edge avenues in computational and theoretical neuroscience. We are using mathematical tools taken from Statistical Physics, Dynamicsl Systems, Machine Learning and Information Theory -- to name just a few -- in order to create new models and theories of brain function. Both analytical approaches and simulations are used heavily. By intense collaborations with experimental laboratories, these new theories and computational tools are put to the test, and then refined further. Our aim is to unravel the basic principles of brain operation and the underlying neural codes.