Pathways from Cell Groups of the Paramedian Tracts to the Floccular Region^a

Abstract

A group of cells lying along the midline of the mid-medulla, nucleus pararaphales, is shown to play a role in vertical eye movements. Its efferents project along the midline, then pass laterally to follow the ventral external arcuate fibers around the surface of the medulla into the restiform body. The fibers terminate in the flocculus and ventral paraflocculus. This nucleus is one of the "cell groups of the paramedian tracts," which, based on their connectivity, could provide a motor-feedback signal for eye-head position to the cerebellum. Lesions of these pathways could lead to gaze-evoked nystagmus.