Chapter 16 - Reticular Formation: Eye Movements, Gaze, and Blinks

Abstract

The word reticular formation refers to its characteristically diffuse structure, a network of loosely packed multipolar neurons, embedded in a dense neuropil. The reticular formation has no distinct cytoarchitectural boundaries, and forms the central core of the brain stem, in which other brain stem nuclei, with clearly outlined cytoarchitectural boundaries, are embedded. It stretches throughout the length of the brain stem, from the mesencephalon through the pons to the medulla oblongata. In the spinal cord, the intermediate zone is recognized through its cytoarchitecture as the continuation of the reticular formation into the spinal cord. The reticular formation of the pons and medulla can be divided into a lateral and a medial tegmental field. The lateral tegmental field contains smaller cells, which are interneurons, or premotor neurons, for the trigeminal, facial, vagal, and hypoglossal motor nuclei. The medial tegmental field contains the premotor circuitry for eye and head movements, and gives rise to descending pathways involved in postural orientation. Furthermore, the brain stem nuclei involved in the generation of eye and head movements, blinks, gaze holding, and their functional neuroanatomy is also discussed.