The lateral longitudinal fascicule is an ascending bundle of axons. The LLF contains fibers of the auditory and mechanosensory systems which originate in the primary sensory brainstem nuclei and terminate in the torus semicircularis. The LLF lies dorsal to the superior reticular formation, adjacent to the ventral rhombencephalic commissure. The LLF becomes displaced more laterally as it approaches the torus semicircularis. The LLF is homologous to the mammalian lateral lemniscus.