Chapter V The cholinergic system in the primate brain: basal forebrain and pontine-tegmental cell groups

Publisher Summary This chapter focuses on the diffuse, ascending cholinergic projection systems, the basal forebrain, and the mesopontine large-celled cholinergic cell groups. In the Nissl-stained sections, the basal forebrain contains a more or less continuous band of magnocellular neurons that begins rostrally at the level of the septum in a medial position and extends caudally and laterally near the anterior commissure. Along its extent, these magnocellular neurons are found either clustered or scattered. The septum in primates contains relatively few neurons (compared to rodents). In the Nissl-stained sections, the parenchyma consists mainly of glial cells, among which are scattered neurons. The medial septal nucleus (MS) is an ill-defined cluster of magnocellular neurons, along the pial border of the structure. The MS disappears at the level of the descent of the columns of the fornix, which coincides approximately with the decussation of the anterior commissure. At this level, the nucleus of the diagonal band of Broca (nDBB) forms a cluster of neurons in the angle between the mid-line and the olfactory tubercle.