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Robotic Spine Universe

Pathways

Dorsal column–medial lemniscus

Fine touch, vibration and position sense

Touch and position sense climb the back of the cord on the same side, in the fasciculus gracilis (legs) and cuneatus (arms). They synapse in the medulla, cross, and travel as the medial lemniscus to the thalamus and on to the sensory cortex.

Drawn for the left side of the body. Schematic route through the model’s landmarks; the pulse speed is illustrative.

Route

served sideother sideCortexDeep brainMidbrainPonsMedullaSpinal cordBody123456

Step by step

  1. Receptor in the skin or joint · served side
  2. Dorsal root, dorsal column (same side) · served side
  3. Nucleus gracilis or cuneatus, then crossing · served side · synapse · crosses the midline
  4. Medial lemniscus · other side
  5. Thalamus · other side · synapse
  6. Primary sensory cortex · other side

Schematic Filled circles: synapses. X: the pathway crosses the midline. Numbers match the list.

Where it runs in the cord (L5)

left fasciculus gracilisright fasciculus gracilisleft fasciculus cuneatusright fasciculus cuneatusleft lateral corticospinal tractright lateral corticospinal tractleft spinal lemniscusright spinal lemniscusleft ventrolateral reticulospinal tractright ventrolateral reticulospinal tractleft ventral corticospinal tractright ventral corticospinal tractleft tectospinal tractright tectospinal tractleft medial reticulospinal tractright medial reticulospinal tractleft medial longitudinal fasciculusright medial longitudinal fasciculusleft ventral hornright ventral hornleft intermediate zoneright intermediate zoneleft dorsal hornright dorsal hornAnteriorPosteriorLR
  • Ascending (sensory)
  • Corticospinal (motor)
  • Other descending
  • Grey matter
Regions in this section (text list)
  • left fasciculus gracilis (focus)
  • right fasciculus gracilis (focus)
  • left fasciculus cuneatus (focus)
  • right fasciculus cuneatus (focus)
  • left lateral corticospinal tract (spared)
  • right lateral corticospinal tract (spared)
  • left spinal lemniscus (spared)
  • right spinal lemniscus (spared)
  • left ventrolateral reticulospinal tract (spared)
  • right ventrolateral reticulospinal tract (spared)
  • left ventral corticospinal tract (spared)
  • right ventral corticospinal tract (spared)
  • left tectospinal tract (spared)
  • right tectospinal tract (spared)
  • left medial reticulospinal tract (spared)
  • right medial reticulospinal tract (spared)
  • left medial longitudinal fasciculus (spared)
  • right medial longitudinal fasciculus (spared)
  • left ventral horn (spared)
  • right ventral horn (spared)
  • left intermediate zone (spared)
  • right intermediate zone (spared)
  • left dorsal horn (spared)
  • right dorsal horn (spared)

Highlighted: the region of the PAM50 white-matter atlas for this pathway, on both sides of the cord. A lesion here takes away what it carries below the level, on the side its fibres serve at that point.

Cut it on the left in the lesion explorer

What the sources say

“The dorsal column is separated into two component tracts, the fasciculus gracilis that contains axons from the legs and lower body, and the fasciculus cuneatus that contains axons from the upper body and arms.” Betts et al. 2022, §14.2
“The axons in the dorsal column terminate in the nuclei of the medulla, where each synapses with the second neuron in their respective pathway.” Betts et al. 2022, §14.2
“These axons then continue to ascend the brain stem as a bundle called the medial lemniscus.” Betts et al. 2022, §14.2

Sources: Betts et al. 2022, §14.2