Locomotion: a tripartite system

The main structures implicated in locomotor control

In mammals, locomotion under healthy conditions emerges from complex, dynamic interactions between three systems.

1. The first includes the supraspinal structures such as the motor cortex, mesencephalic locomotor region, and cerebellum, which contribute to voluntary control and modulation of locomotion.

2. The second consists of spinal networks, including the central pattern generator (CPG) and other circuits such as propriospinal pathways and local reflexes. The CPG organizes temporal and spatial activation of limb muscles, propriospinal pathways coordinate movements between limbs, and reflexes refine and adjust locomotor patterns.

3. The third system involves somatosensory feedback from cutaneous, muscle, tendon, and joint receptors. These inputs continuously inform the nervous system about the body's position and interaction with the environment and adjust the locomotor pattern accordingly.