The lateral lemniscus is located where the cochlear nuclei and the pontine reticular formation PRF crossover. The PRF descends the reticulospinal tract where it innervates motor neurons and spinal interneurons. It is the main auditory tract in the brainstem that connects the superior olivary complex SOC with the inferior colliculus IC. There are three small nuclei on each of the lateral lemnisci: the ventral, dorsal, and the intermediate.
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Path[ edit ] After neurons carrying proprioceptive or fine touch information synapse at the gracile and cuneate nuclei, axons from secondary neurons decussate at the level of the medulla and travel up the brainstem as the medial lemniscus on the contralateral opposite side. It is part of the posterior column-medial lemniscus pathway , which transmits touch, vibration sense, as well as the pathway for proprioception.
The medial lemniscus carries axons from most of the body and synapses in the ventral posterolateral nucleus of the thalamus , at the level of the mamillary bodies.
Sensory axons transmitting information from the head and neck via the trigeminal nerve synapse at the ventral posteromedial nucleus of the thalamus. Location through the brainstem[ edit ] The cuneate and gracile nuclei reside at the closed lower medulla , so the lemniscus is not formed at this level. Fibres from these nuclei will pass to the contralateral side of the brainstem, as the internal arcuate fibres. At the open medulla further up the brainstem , the medial lemniscus contains axons from the trigeminal nerve which supplies the head region , as well as the arms and legs.
It sits very close to the midline, at the same orientation of the midline, with head fibres more dorsal closer to the back , towards the fourth ventricle. By mid- pons , the medial lemniscus has rotated. Fibres from the head are medial, fibres from the leg are lateral. The orientation in the midbrain is similar to that in the pons.