Which neural circuits are involved in gait initiation and associated anticipatory postural adjustments (APAs)?

• A. Cerebellum and basal ganglia only
• B. Spinal reflex pathways only
• C. Cerebellum, basal ganglia, supplementary motor area, and brainstem networks coordinating pre-movement postural adjustments
• D. Occipital and parietal cortex only

Answer: (C)

Gait initiation with anticipatory postural adjustments relies on an integrated network that links planning, timing, and posture with the upcoming step. The supplementary motor area plans and organizes internally guided movements and communicates with motor pathways to start stepping. The basal ganglia help select and initiate the correct gait pattern, regulate the vigor and sequence of actions, and suppress competing movements. The cerebellum provides predictive timing and fine-tuning, ensuring APAs are scaled properly and occur just before the step. Brainstem networks, especially reticulospinal and vestibulospinal systems, carry out the actual pre-movement postural adjustments, coordinating trunk and proximal muscles to shift the center of mass in advance of stepping. This combination explains why just spinal reflexes or only sensory cortices like the occipital or parietal areas aren’t enough—the motor planning and automatic postural control circuits are essential for initiating gait and producing APAs.