The medial lemniscus is a pathway in the brainstem that carries sensory information from the gracile and cuneate nuclei to the thalamus. The fibers of the medial lemniscus take origin in the gracile and cuneate nuclei of the medulla oblongata, and as internal arcuate fibers they cross to the opposite side in the sensory decussation. They then pass in the interolivary stratum upward through the medulla oblongata, in which they are situated behind the cerebrospinal fibers and between the olives. In the pons and lower part of the mid-brain it occupies the ventral part of the reticular formation and tegmentum close to the raphe, while above it gradually shifts to the dorso-lateral part of the tegmentum in the angle between the red nucleus and the substantia nigra. In the pons it assumes a flattened ribbon-like appearance, and is placed dorsal to the trapezium. As the lemniscus ascends, it receives additional fibers from the terminal sensory nuclei of the cranial nerves of the opposite side. Many of the fibers which arise from the terminal sensory nuclei of the cranial nerves pass upward in the formatio reticularis as a separate bundle, known as the central tract of the cranial nerves, to the thalamus.

This definition incorporates text from a public domain edition of Gray's Anatomy (20th U.S. edition of Gray's Anatomy of the Human Body, published in 1918 – from


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