Anterior spinocerebellar tract

At a glance

English

Anterior spinocerebellar tract

Latin (TA2)

Tractus spinocerebellaris anterior

System

Brain and spinal cord

Region

Whole body

Side

Single, on the midline

About the anterior spinocerebellar tract

The anterior (ventral) spinocerebellar tract is one of the routes by which the spinal cord tells the cerebellum what the body is doing. Its fibres run upwards in a thin band along the front part of the outer surface of the lateral funiculus, next to the posterior spinocerebellar tract. It is sometimes named Gowers' tract, after the neurologist William Gowers. Its information never reaches awareness; it is used to co-ordinate posture and movement.

The pathway uses two neurons. The first is a sensory cell in a dorsal root ganglion, whose central process enters through the dorsal rootlets. In the lumbosacral cord, below about L2 or L3, it ends on cells in the grey matter around the base of the posterior horn and the intermediate zone, the region often called the spinal border cells. These second neurons send their axons across the midline in the anterior white commissure, then upwards in the opposite lateral funiculus.

The tract climbs the whole cord and the medulla and reaches the upper pons. There it turns back over the superior cerebellar peduncle, unlike most spinal input, which uses the inferior peduncle. Inside the cerebellar white matter most fibres cross the midline a second time, so they finish on the same side as the limb they began from. This double crossing earns the tract its nickname, the double crosser. Fibres finish in the anterior lobe cortex and in the vermis, giving branches to the emboliform and globose nuclei on the way.

Experiments in walking cats suggest a difference in role from its posterior partner. When the dorsal roots were cut, the posterior tract fell silent while the anterior tract kept firing. The anterior tract therefore seems to report the activity of the spinal motor circuits themselves, a copy of the movement command, rather than raw input from the muscles. Damage to the lateral funiculus, as in hereditary spinocerebellar degenerations, contributes to unsteady walking.

Function and supply

Function

Carries unconscious information about lower-limb movement, mainly the activity of spinal motor circuits during stepping, to the cerebellum for co-ordinating posture and gait.

Blood supply

Runs in the territory of the anterior spinal artery along most of the cord, with contributions from the arterial vasocorona at the surface.