Medial Lemniscus - Wikipedia

Ascending bundle of axons which cross in the brainstem

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 the lentiform nucleus and insula. "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[edit on Wikidata]

The medial lemniscus, also known as Reil's band or Reil's ribbon (for German anatomist Johann Christian Reil), is a large ascending bundle of heavily myelinated axons that decussate in the brainstem, specifically in the medulla oblongata. The medial lemniscus is formed by the crossings of the internal arcuate fibers. The internal arcuate fibers are composed of axons of the gracile nucleus and the cuneate nucleus. The cell bodies of the nuclei lie contralaterally.

The medial lemniscus is part of the somatosensory dorsal column–medial lemniscus pathway, which ascends in the spinal cord to the thalamus.[1] Lesions of the medial lemniscus cause an impairment of vibratory and touch-pressure sense.

Etymology

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Lemniscus means "ribbon", reflecting the elongated tract of the medial lemniscus.[2]

Anatomy

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Path

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After neurons carrying somatosensory proprioceptive or fine touch information synapse at the gracile and cuneate nuclei, axons from second-order 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.[citation needed]

The medial lemniscus carries axons from most of the body and terminates by synapsing with third-order neurons in the ventral posterolateral nucleus of the thalamus.[3] 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

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The cuneate and gracile nuclei reside at the closed (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 the internal arcuate fibres. In the midbrain, it is situated dorsal to the substantia nigra, and medial to either red nucleus.[4]

Additional images

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• Horizontal section through the lower part of the pons. The medial lemniscus is labeled #17.
• Tractography showing medial lemniscus

References

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1. ^ Kamali A, Kramer LA, Butler IJ, Hasan KM. Diffusion tensor tractography of the somatosensory system in the human brainstem: initial findings using high isotropic spatial resolution at 3.0 T. Eur Radiol. 2009 19:1480-8. doi:10.1007/s00330-009-1305-x.
2. ^ Purves, Dale (2012). Neuroscience (5th ed.). Sunderland, Mass: Sinauer Associates. p. 198. ISBN 9780878936953.
3. ^ Purves, Dale (2018). Neuroscience (Sixth ed.). New York: Oxford University Press. pp. 202–204. ISBN 9781605353807.
4. ^ "medial lemniscus - Dictionnaire médical de l'Académie de Médecine". www.academie-medecine.fr. Retrieved 2024-07-27. 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.

External links

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• Stained brain slice images which include the "medial lemniscus" at the BrainMaps project

v t e Anatomy of the medulla
Grey matter	Cranial nuclei afferent: Solitary nucleus tract Dorsal respiratory group Gustatory nucleus Vestibular nuclei Lateral Medial Inferior efferent: Hypoglossal nucleus Nucleus ambiguus Dorsal nucleus of vagus nerve Inferior salivatory nucleus Dorsal Gracile nucleus Cuneate nucleus Accessory cuneate nucleus Ventral Ventral respiratory group Arcuate nucleus of medulla Rostral ventromedial medulla Botzinger complex Pre-Bötzinger complex
White matter	Dorsal Sensory Sensory decussation Medial lemniscus Juxtarestiform body Ascending dorsal longitudinal fasciculus Medial longitudinal fasciculus Motor Descending dorsal longitudinal fasciculus Medial longitudinal fasciculus Ventral Descending tracts Olivocerebellar tract Rubro-olivary tract
Surface	Front Pyramid Anterior median fissure Anterolateral sulcus Olive Inferior olivary nucleus Back Posterior median sulcus Posterolateral sulcus Area postrema Vagal trigone Hypoglossal trigone Medial eminence Inferior cerebellar peduncle
Grey	Reticular formation Gigantocellular Parvocellular Ventral Lateral Paramedian Raphe nuclei Obscurus Magnus Pallidus Perihypoglossal nuclei

v t e Anatomy of the pons
Dorsal/(tegmentum)	Surface Cerebellopontine angle Superior medullary velum Sulcus limitans Medial eminence Facial colliculus White: Sensory Trapezoid body Trigeminal lemniscus Dorsal trigeminal tract Ventral trigeminal tract Medial lemniscus Lateral lemniscus Central tegmental tract Medial longitudinal fasciculus Vestibulo-oculomotor fibers White: Motor Inferior cerebellar peduncle Vestibulocerebellar tract Medial longitudinal fasciculus Vestibulospinal tract Medial vestibulospinal tract Lateral vestibulospinal tract Grey: Cranial nuclei afferent: GSA Trigeminal Principal Spinal Cochlear nucleus Dorsal Anterior Vestibular nuclei Superior efferent: SVE: Trigeminal motor nucleus Facial motor nucleus GSE: Abducens nucleus GVE: Superior salivary nucleus Inferior salivary nucleus Grey: Other nuclei Pedunculopontine nucleus Apneustic center Pneumotaxic center Parabrachial nuclei Subparabrachial nucleus Medial parabrachial nucleus Lateral parabrachial nucleus Superior olivary nucleus Locus coeruleus
Ventral/(base)	Grey Pontine nuclei White: Motor/descending Corticospinal tract Corticobulbar tract Corticopontine fibers MCP Pontocerebellar fibers Surface Basilar sulcus
Other grey: Raphe/reticular	Reticular formation Caudal Oral Tegmental Paramedian Raphe nuclei Median

v t e Anatomy of the midbrain
Tectum(Dorsal)	Corpora quadrigemina Inferior colliculus Inferior brachium Superior colliculus Superior brachium Grey matter Pretectal area White matter Sensory / ascending Spinotectal tract Central tegmental tract Motor / descending Tectospinal tract
CSF	Cerebral aqueduct
Peduncle(Ventral)	Tegmentum White matter Sensory / ascending Lemnisci Medial Lateral Ascending MLF Vestibulo-oculomotor fibers Spinothalamic tract Ventral trigeminal tract Dentatothalamic tract Motor / descending Rubrospinal tract Rubro-olivary tract Descending MLF Grey matter cranial nuclei GSA Mesencephalic GSE Oculomotor nucleus Trochlear nucleus GVE Edinger–Westphal nucleus Ventral tegmental area Rostromedial tegmental nucleus Periaqueductal gray Red nucleus Rostral interstitial nucleus of medial longitudinal fasciculus Parabrachial area Interpeduncular nucleus Midbrain reticular formation Dorsal tegmental nucleus Raphe nuclei dorsal Reticulotegmental nucleus Base White / Cerebral crus Pyramidal tracts Corticospinal tract Corticobulbar tract Corticopontine tract Frontopontine fibers Temporopontine fibers Grey / Substantia nigra Pars compacta Pars reticulata Surface Superior cerebellar peduncle Decussation Interpeduncular fossa

v t e Brain and spinal cord: neural tracts and fasciculi
Sensory	DCML 1°: Pacinian corpuscle/Meissner's corpuscle → Posterior column (Gracile fasciculus/Cuneate fasciculus) → Gracile nucleus/Cuneate nucleus 2°: → sensory decussation/arcuate fibers (Posterior external arcuate fibers, Internal arcuate fibers) → Medial lemniscus/Trigeminal lemniscus → Thalamus (VPL, VPM) 3°: → Posterior limb of internal capsule → Postcentral gyrus Anterolateral/pain Fast/lateral 1° (Free nerve ending → A delta fiber) → 2° (Anterior white commissure → Lateral and Anterior Spinothalamic tract → Spinal lemniscus → VPL of Thalamus) → 3° (Postcentral gyrus) → 4° (Posterior parietal cortex) 2° (Spinomesencephalic tract → Superior colliculus of Midbrain tectum) Slow/medial 1° (Group C nerve fiber → Spinoreticular tract → Reticular formation) → 2° (MD of Thalamus) → 3° (Cingulate cortex)
Motor	Pyramidal flexion: Primary motor cortex → Posterior limb of internal capsule → Decussation of pyramids → Corticospinal tract (Lateral, Anterior) → Neuromuscular junction Extrapyramidal flexion: Primary motor cortex → Genu of internal capsule → Corticobulbar tract → Facial motor nucleus → Facial muscles flexion: Red nucleus → Rubrospinal tract extension: Vestibulocerebellum → Vestibular nuclei → Vestibulospinal tract extension: Vestibulocerebellum → Reticular formation → Reticulospinal tract Midbrain tectum → Tectospinal tract → muscles of neck Basal ganglia direct: 1° (Motor cortex → Striatum) → 2° (GPi) → 3° (Lenticular fasciculus/Ansa lenticularis → Thalamic fasciculus → VL of Thalamus) → 4° (Thalamocortical radiations → Supplementary motor area) → 5° (Motor cortex) indirect: 1° (Motor cortex → Striatum) → 2° (GPe) → 3° (Subthalamic fasciculus → Subthalamic nucleus) → 4° (Subthalamic fasciculus → GPi) → 5° (Lenticular fasciculus/Ansa lenticularis → Thalamic fasciculus → VL of Thalamus) → 6° (Thalamocortical radiations → Supplementary motor area) → 7° (Motor cortex) nigrostriatal pathway: Pars compacta → Striatum
Cerebellar	Afferent Vestibular nuclei → Vestibulocerebellar tract → ICP → Cerebellum → Granule cell Pontine nuclei → Pontocerebellar fibers → MCP → Deep cerebellar nuclei → Granule cell Inferior olivary nucleus → Olivocerebellar tract → ICP → Hemisphere → Purkinje cell → Deep cerebellar nuclei Efferent Dentate nucleus in Lateral hemisphere/pontocerebellum → SCP → Dentatothalamic tract → Thalamus (VL) → Motor cortex Interposed nucleus in Intermediate hemisphere/spinocerebellum → SCP → Reticular formation, or → Cerebellothalamic tract → Red nucleus → Thalamus (VL) → Motor cortex Fastigial nucleus in Flocculonodular lobe/vestibulocerebellum → Vestibulocerebellar tract → Vestibular nuclei Bidirectional:Spinocerebellar Unconscious proprioception lower limb → 1° (muscle spindles → DRG) → 2° (Posterior thoracic nucleus → Dorsal/posterior spinocerebellar tract → ICP → Cerebellar vermis) upper limb → 1° (muscle spindles → DRG) → 2° (Accessory cuneate nucleus → Cuneocerebellar tract → ICP → Anterior lobe of cerebellum) Reflex arc lower limb → 1° (Golgi tendon organ) → 2° (Ventral/anterior spinocerebellar tract→ SCP → Cerebellar vermis) upper limb → 1° (Golgi tendon organ) → 2° (Rostral spinocerebellar tract → ICP → Cerebellum)

v t e Sensory receptors
Touch	Mechanoreceptor Vibration Lamellar corpuscle Light touch Tactile corpuscle Pressure Merkel nerve ending Stretch Bulbous corpuscle
Pain	Free nerve ending Nociceptors
Temperature	Thermoreceptors
Proprioception	Golgi organ Muscle spindle Intrafusal muscle fiber Nuclear chain fiber Nuclear bag fiber
Other	Hair cells Baroreceptor

Authority control databases	Terminologia Anatomica 2 3