The dorsal column nuclei are a pair of nuclei in the dorsal columns of the dorsal column–medial lemniscus pathway (DCML) in the brainstem.
Structure
Nerve pathways
The dorsal column nuclei each have an associated
nerve tract in the
spinal cord, the gracile fasciculus and the cuneate fasciculus, together forming the
dorsal columns. Both dorsal column nuclei contain synapses from afferent nerve fibers that have travelled in the spinal cord.
They then send on second-order
of the dorsal column–medial lemniscal pathway.
Neurons of the dorsal column nuclei eventually reach the midbrain and the thalamus.
Nuclei
The major nuclei are the cuneate nucleus and gracile nucleus.
These are present at the bottom of the medulla oblongata.
Gracile nucleus
The
gracile nucleus is medial to the cuneate nucleus.
Its neurons receive afferent input from dorsal root ganglia
of the lower
torso and the
Human leg.
The gracile nucleus and gracile fasciculus carry
epicritic,
kinesthetic, and conscious
proprioceptive information from the lower part of the body (below the level of T6 in the spinal cord). Because of the large population of neurons in the gracile nucleus they give rise to a raised area called the
gracile tubercle on the posterior side of the closed medulla at the floor of the
fourth ventricle.
Cuneate nucleus
The
cuneate nucleus is lateral to the gracile nucleus.
It carries the same type of information, but from the upper body and the
Upper limb (except the
face, which is carried by the principal sensory nucleus of trigeminal nerve).
The cuneate nucleus is wedge-shaped and located in the closed part of the medulla. It lies lateral to the gracile nucleus and medial to the spinal trigeminal nucleus in the medulla. The large number of neurons found there give rise to the
cuneate tubercle seen on viewing the posterior aspect of the medulla on the side of the
brainstem.
Function
The dorsal column nuclei help to carry
touch and
proprioception information from the body to the
brain. The gracile nucleus carries information from the lower
torso and the
Human leg.
The cuneate nucleus carries information from the upper body and the
Upper limb.
Clinical significance
The dorsal column nuclei may degenerate during
ageing, although evidence for this is not conclusive.
This may reduce the sensitivity of
touch and
proprioception.
Other animals
In some other animals, a third nucleus is present, known as the median accessory nucleus.
This may carry information from the
tail.
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