| Medial lemniscus | |
|---|---|
 The sensory tract. (Medial lemniscus labeled at top right.) | |
 Coronal section through mid-brain. ("e" is Portion of medial lemniscus, which runs to thelentiform nucleus andinsula. "a’" is also the medial lemniscus.) | |
| Details | |
| Identifiers | |
| Latin | lemniscus medialis |
| NeuroLex ID | birnlex_887 |
| TA98 | A14.1.04.111 A14.1.08.672 A14.1.06.207 |
| TA2 | 5861 |
| FMA | 83675 |
| Anatomical terms of neuroanatomy | |
Themedial lemniscus, also known asReil's band orReil's ribbon (for German anatomistJohann Christian Reil), is a large ascending bundle of heavily myelinated axons thatdecussate in thebrainstem, specifically in themedulla oblongata. The medial lemniscus is formed by thecrossings of theinternal arcuate fibers. The internal arcuate fibers are composed of axons of thegracile nucleus and thecuneate nucleus. Thecell bodies of the nuclei lie contralaterally.
The medial lemniscus is part of thesomatosensorydorsal column–medial lemniscus pathway, which ascends in thespinal cord to thethalamus.[1] Lesions of the medial lemniscus cause an impairment of vibratory and touch-pressure sense.
Lemniscus means "ribbon", reflecting the elongated tract of the medial lemniscus.[2]
After neurons carryingsomatosensory proprioceptive or fine touch informationsynapse at the gracile and cuneate nuclei, axons fromsecond-order neuronsdecussate at the level of the medulla and travel up the brainstem as the medial lemniscus on the contralateral (opposite) side. It is part of theposterior column-medial lemniscus pathway, which transmits touch, vibration sense, as well as thepathway for proprioception.[citation needed]
The medial lemniscus carries axons from most of the body and terminates by synapsing withthird-order neurons in theventral posterolateral nucleus of thethalamus.[3] at the level of themamillary bodies. Sensory axons transmitting information from the head and neck via thetrigeminal nerve synapse at theventral posteromedial nucleus of thethalamus.
The cuneate and gracile nuclei reside at theclosed (lower)medulla, so the medial lemniscus is not formed at this level. Fibres from these nuclei will pass to the contralateral side of the brainstem, as theinternal arcuate fibres. In the midbrain, it is situated dorsal to thesubstantia nigra, and medial to eitherred nucleus.[4]
