Introduction

Abstract

In our attempts to interrogate Nature about the development of the nervous system, we ask such questions as “How do the nerve cells originate and how do the correct types of cells differentiate at their correct positions; how do the neurons link together to form circuits whose functions are properly coordinated; and how are the functions of nerve cells related to behavior, to thought, and to consciousness?” Those problems are intellectually challenging, not only because solving them would give us practical advantages but also because while they remain unsolved they stimulate the imagination and challenge the intelligence. It is precisely because they are difficult and controversial and have defied complete solution that such problems continue to attract subtle minds.