The Medial Forebrain Bundle and Related Hypothalamic Connections

Abstract

The medial forebrain bundle is a long, loosely textured fiber system which interconnects a variety of structures of the limbic and olfactory forebrain with the hypothalamus and the midbrain tegmentum. The parasagittal section reproduced in Figure 8-1 shows the major body of this rather massive fiber system as it passes caudally from the level of the anterior commissure to the posterior borders of the mammillary complex. As will be seen later, the more anterior and posterior projections of this system are somewhat more diffuse, and the various components of this system must be considered separately. Figure 8-2 shows this bundle of fibers in cross section at the level of the optic chiasm. At this level, and in fact throughout the system, the fibers are not seen as a compact bundle but rather are interspersed among cell bodies; in this particular instance, the cell bodies are those of the lateral hypothalamic nucleus.