Spinocerebellar tracts

In this note, we will continue discussing the anatomy and function of the tracts of the brain and spinal cord.

Let’s look at the spinocerebellar tracts:

Anterior

Posterior

and the so-called cuneocerebellar.

They represent the ascending pathways and carry sensory (afferent) information from peripheral receptors to the structures of the central nervous system for further processing.

Let’s start by defining the function.

These tracts carry information from proprioceptors (in particular the Golgi tendon organs and muscle spindles) and from some exteroceptors about the position of body parts to the cerebellum.

This sensation allows us to subconsciously control the position of muscles, tendons, and joints in space, providing movement coordination and maintenance of posture.

The spinocerebellar tracts have first- and second-order neurons.

Let’s discuss the posterior spinocerebellar tract: fibers from receptors are directed to the spinal ganglion, where they synapse with the first-order neuron of this pathway.

Then, the fibers enter directly into the spinal cord via the dorsal root, into the posterior horn.

The posterior thoracic nucleus also known as the dorsal nucleus of Clarke, which contains the second-order neuron of this pathway, is located in the spinal cord segments from C8 to L2/L3.

After this, the fibers ascend in the lateral funiculus of the spinal cord,

pass through the inferior cerebellar peduncle, and terminate in the anterior and posterior parts of the vermal cortex.

Since the posterior thoracic nucleus is absent in the cervical region of the spinal cord, the posterior spinocerebellar tract carries proprioceptive information only from the lower limbs and trunk.

In this regard, it is necessary to recall the anatomy of the dorsal column–medial lemniscus pathway.

Some fibers of the cuneate fasciculus

in the medulla oblongata synapse with the second-order neuron not in the cuneate nucleus but in the so-called accessory cuneate nucleus. The posterior external arcuate fibers then arise from it and form the cuneocerebellar tract, which travels toward the inferior cerebellar peduncle.

The cells of the accessory cuneate nucleus and the posterior thoracic nucleus are similar in their structure, so it can be said that the cuneocerebellar tract is an analog of the posterior spinocerebellar tract, but for the upper limbs.

Eventually, both tracts form a network of so-called mossy fibers that terminate in the cerebellar cortex.

Let’s examine the anterior spinocerebellar tract.

Fibers from receptors are directed to the spinal ganglion, where they synapse with the first-order neuron.

The second-order neuron is also located in the posterior horn of the spinal cord, but below the level of L2/L3.

After synapsing, the pathway crosses over to the opposite side (decussates) into the lateral funiculus, specifically into its more anterior sections.

It then ascends to the level of the upper pons, decussates back to the side of the receptors through the superior cerebellar peduncle, and terminates in the anterior part of the vermal cortex.

Golosary