Notes on techniques

Abstract

In this introductory chapter, techniques for studying brain circuitry will be discussed. Many features of the fibre connections of the human brain and spinal cord have been elucidated by the analysis of normal preparations stained by the Weigert-Pal and Klüver-Barrera techniques in order to demonstrate the myelin sheaths around axons of neurons (Sect. 3.2). Brain circuitry can be studied with these myelin-staining techniques, the classic Marchi and Nauta degeneration techniques and the more recent tract-tracing techniques (Sect. 3.3), with immunohistochemistry (Sect. 3.4) as well as with various electrophysiological techniques (Sect. 3.5). The development of modern non-invasive imaging techniques (Sect. 3.6) such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) has greatly improved our knowledge of the circuitry of the human central nervous system (CNS). New developments in MR imaging such as diffusion MRI (dMRI; “tractography”) allow the visualization of the major fibre connections in the human CNS. These various techniques are illustrated with examples on the corticospinal tract and long association pathways. Section 3.7 includes a brief discussion of what became to be known as the human connectome.