Morphological Approaches to the Anatomical Dissection of Neuronal Circuits

The purpose of this introductory chapter is to provide an overview of a number of techniques used to study the brain’s anatomical organization, with particular focus on the investigation of the mammalian neocortex, the large outer surface of the brain and the key structure responsible for complex perceptual and cognitive abilities of mammals. I briefly examine how traditional and more recently developed methods involving histochemistry, neuronal tracing, cell morphology and photostimulation are being used to reveal cortical anatomy at broad and very fine levels of specificity. In addition, in the last section, I review recent advances in neuronal tracing technology that capitalize on the neurotropic properties of rabies virus to enable retrograde labeling of neural circuits at single cell resolution. In the chapters that follow, detailed descriptions of new methodologies for characterizing neuronal cell populations (Herculano-Houzel), as well as high-resolution techniques for mapping local cortical networks (Radkinow et al) are discussed. These approaches are proving to be invaluable in unraveling the many neuroanatomical issues that remain unresolved.