praecentralis

Praecentralis is a Latin anatomical term meaning “before the center,” most often encountered in the form of gyrus praecentralis, the precentral gyrus. In human neuroanatomy, the precentral gyrus is the primary motor cortex of the frontal lobe. It lies immediately anterior to the central sulcus, separating the frontal lobe from the parietal lobe, with the paracentral lobule representing its medial extension on the frontal surface and the orbital part of the inferior frontal gyrus lying nearby.

The precentral gyrus houses neurons that initiate voluntary movements. It exhibits a somatotopic organization, commonly described as a motor homunculus, where different body parts are controlled by distinct regions along the gyrus, with the face and hands represented laterally and the leg more medially. The principal output originates from large Betz cells in layer V, sending axons through the corticospinal tract to spinal motor neurons, enabling skilled, purposeful movements. It receives input from premotor and supplementary motor areas, integrating planning with execution.

Brodmann area 4 is typically associated with the primary motor cortex housed in the precentral gyrus, while adjacent premotor areas (e.g., area 6) participate in motor planning. Clinically, lesions affecting the precentral gyrus can produce contralateral weakness or paralysis, particularly of movements governed by the affected region, and may yield upper motor neuron signs if the corticospinal tract is involved.

Praecentralis thus principally denotes the frontal lobe motor region, most commonly identified with the precentral gyrus in contemporary neuroanatomy.