All parts of the brain › Pathways › Dorsal column–medial lemniscus pathway

Where does the dorsal column–medial lemniscus pathway run?

Fine touch, vibration and limb position climb the dorsal columns of the spinal cord on their own side to the medulla, cross there and run on as the medial lemniscus through the pons and midbrain to the thalamus, which relays them to the postcentral gyrus. [1][2]

A tract has no shape of its own in this atlas; lit: the parts it runs through, in order.

The 3D brain needs JavaScript. The steps below still say where the dorsal column–medial lemniscus pathway runs, in order.

Lit: the six parts the pathway runs through, from the spinal cord up to the cortex.

Route Slice

The brain starts seen from the left, a little from the front and below, so the brainstem the fibres climb and the gyrus they reach behind the central sulcus both show. Step through lights one step at a time, about 1.2 s each, bottom to top; tap a step below to light it alone. Drag to turn, pinch or scroll to zoom.

Each step lights the whole part, not the bundle inside it: the atlas has no shape for the dorsal columns, the gracile and cuneate nuclei or the medial lemniscus. At the first step it has only the top of the spinal cord, drawn as its thin central canal. [3][1]

The route, in 6 steps

Fine-touch, vibration and position fibres enter through the dorsal roots and, without a synapse, turn straight up the dorsal (posterior) columns on their own side: the fasciculus gracilis carries the leg and lower body, and the fasciculus cuneatus, added beside it from about the sixth thoracic segment up, the arm and upper body. [1][4] Where is the spinal cord?
The first-order fibres end in the lower medulla, in the gracile and cuneate nuclei at its back. The second-order neurons start here. [1][2] Where is the medulla oblongata?
Crossing in the medulla (the sensory decussation): the second-order axons sweep forward as the internal arcuate fibres, cross the midline and turn up on the other side as the medial lemniscus. Below this point the pathway carries its own side of the body; above it, the opposite side. The atlas has no shape for the crossing, so it is not marked. [2][1]
The medial lemniscus climbs through the tegmentum of the pons. Near the midline of the medulla it was an upright band; through the pons it turns into a flatter band lying from side to side. [2][5] Where is the pons?
It continues up through the midbrain tegmentum, now further out towards the side, next to the spinothalamic fibres. [2] Where is the midbrain?
The medial lemniscus ends in the ventral posterolateral (VPL) nucleus of the thalamus, on the third-order neurons of the pathway. [1][6] Where is the thalamus?
From the VPL nucleus the third-order axons pass through the internal capsule to the postcentral gyrus, the primary somatosensory cortex (Brodmann areas 3, 1 and 2), where each body part of the opposite side has its own patch. [1][7] Where is the postcentral gyrus?

More about the dorsal column–medial lemniscus pathway

Other names: dorsal column pathway, posterior column–medial lemniscus pathway, DCML, PCML, lemniscal pathway [1]

How it differs from the spinothalamic tract: this pathway carries fine (discriminative) touch, vibration and the sense of where the limbs are, climbs the spinal cord uncrossed and crosses only in the medulla; the spinothalamic tract carries pain, temperature and crude touch and crosses in the spinal cord. The two meet again in the ventral posterolateral nucleus of the thalamus and the postcentral gyrus. [1][8][4] Where does the spinothalamic tract run?

It carries fine touch, two-point discrimination, vibration and conscious proprioception, the felt sense of where the limbs are. [1]
Its first neuron is very long: a fibre from the foot runs from the skin, through the dorsal root and all the way up the spinal cord to the lower medulla before its first synapse. [1]
The dorsal columns are layered by body region: the fibres from the lowest segments lie nearest the midline, and each higher segment adds its fibres on the outside. [1]
Fine touch from the face does not use the dorsal columns: it reaches the thalamus through the trigeminal nerve, ending in the ventral posteromedial (VPM) nucleus. [6]

Pain and temperature reach the same cortex by a second route, the spinothalamic tract. Every part that registers touch, temperature and pain, lit together with its role: What part of the brain feels touch, temperature and pain?

Sources

Facts describe anatomy and normal function only. The 3D model is the adult male BodyParts3D brain (credits and licence); it has no shape for tracts, so a pathway is shown by the parts it runs through.