Which Brain Parts Control Movement?

Movement control involves multiple brain regions working in coordination. The primary motor cortex initiates voluntary movements, while the basal ganglia select and modulate actions, the cerebellum fine-tunes coordination, and the brainstem maintains balance and posture.

The Primary Motor Cortex: Your Movement Command Center

The primary motor cortex, located in the precentral gyrus of the frontal lobe, serves as the main output center for voluntary movement. This region sends direct signals through the corticospinal tract to spinal motor neurons, which then activate skeletal muscles. What makes this area remarkable is its somatotopic organization—a body map where different sections control specific body parts.

The motor homunculus reveals an interesting pattern: body parts requiring precise control occupy disproportionately large areas. Your hands and face, which perform intricate movements, take up significantly more cortical space than your trunk or legs. This explains why you can thread a needle but can’t perform similarly delicate tasks with your elbow.

Research has shown that neurons in the primary motor cortex don’t control individual muscles in isolation. Instead, they coordinate complex movements involving multiple muscle groups. When you reach for a cup, motor cortex neurons orchestrate the synchronized action of shoulder, elbow, wrist, and finger muscles to produce one fluid motion.

The primary motor cortex works through two major pathways. The corticospinal tract sends signals to your spinal cord to control body movements, while the corticobulbar tract controls facial, jaw, and tongue movements. About 40% of the pyramidal tract fibers originate from the primary motor cortex, with additional contributions from premotor, somatosensory, and posterior parietal areas.

Premotor and Supplementary Motor Areas: Planning Your Next Move

Before any movement begins, your brain must plan it. The premotor cortex and supplementary motor area, located anterior to the primary motor cortex in Brodmann area 6, handle this critical preparation phase.

The premotor cortex specializes in preparing movements, particularly of proximal muscles like those in your shoulders and upper arms. It integrates sensory information to guide movements based on external cues. When you see a doorknob and reach for it, your premotor cortex processes the visual information and prepares the appropriate motor response.

The supplementary motor area takes on a different role. It’s involved in planning sequences of movements and coordinating actions between both sides of your body. Learning to play a musical instrument provides a clear example—the supplementary motor area helps you plan the sequence of finger movements and coordinate your left and right hands.

These regions don’t send signals directly to spinal motor neurons like the primary motor cortex does. Instead, they project to brainstem areas and work through indirect pathways, controlling movements by modulating the activity of other motor centers. This hierarchical organization allows for sophisticated motor planning while maintaining direct execution pathways for immediate responses.

Basal Ganglia: The Movement Selection System

Deep beneath the cerebral cortex lies the basal ganglia, a cluster of interconnected nuclei that acts as a gatekeeper for movement. The main components include the striatum (caudate nucleus and putamen), globus pallidus, substantia nigra, and subthalamic nucleus.

The basal ganglia operates through two pathways that work in opposition. The direct pathway facilitates desired movements by reducing inhibition on the thalamus, which then activates the motor cortex. The indirect pathway suppresses unwanted movements by increasing inhibition. This dual system ensures that only appropriate movements are executed while competing actions are suppressed.

Think of the basal ganglia as a sophisticated selection mechanism. When you’re at a busy intersection deciding whether to cross, your basal ganglia weighs multiple potential actions—walk forward, step back, turn left—and selects the most appropriate response while inhibiting alternatives.

Dopamine plays a crucial role in this system. Neurons in the substantia nigra pars compacta release dopamine into the striatum, modulating the balance between the direct and indirect pathways. When dopamine levels drop, as in Parkinson’s disease, patients experience bradykinesia—extreme slowness of movement. The basal ganglia can no longer properly facilitate voluntary actions.

The system also influences movement speed. Research indicates that the basal ganglia control the rate of change in body configurations. Reduced dopamine signaling decreases the velocity reference signal, resulting in slower transitions from one posture to another.

Cerebellum: The Coordination Specialist

Located at the back of your brain, beneath the occipital lobes, the cerebellum looks like a separate miniature brain. Despite comprising only 10% of brain volume, it contains more than 50% of the brain’s neurons—approximately 50 billion in total.

The cerebellum doesn’t initiate movement. Instead, it receives copies of motor commands from the cortex and sensory feedback about actual movement from the periphery, then compares the two. When discrepancies exist between intended and actual movement, the cerebellum sends corrective signals to adjust ongoing actions.

This error-detection system enables smooth, coordinated movements. When you first learn to ride a bicycle, your movements are jerky and uncoordinated. The cerebellum detects these motor errors and gradually refines your control through practice. Eventually, the movements become automatic and fluid.

The cerebellum’s internal circuitry is uniquely organized. Purkinje cells receive input from up to 100 million parallel fibers, then funnel their output to a small group of deep cerebellar nuclei. This massive convergence allows the cerebellum to integrate enormous amounts of sensory information and make rapid adjustments to movement.

Damage to the cerebellum produces characteristic symptoms. Patients develop ataxia—a lack of coordination that affects gait, speech, and limb movements. They struggle with dysmetria, consistently overshooting or undershooting targets. Intention tremor appears at the end of movements, and they lose the ability to perform rapidly alternating movements.

Recent research reveals that the cerebellum does more than coordinate movement. It participates in motor learning, contributes to cognitive functions like attention and language, and even influences emotional regulation. The cerebellum’s connections extend throughout the brain, forming closed-loop circuits with the motor cortex, basal ganglia, and prefrontal regions.

Brainstem: Maintaining Posture and Balance

The brainstem, connecting your brain to the spinal cord, houses critical centers for postural control and balance. Three main regions—the midbrain, pons, and medulla—coordinate automatic adjustments that keep you stable during movement.

Upper motor neurons in the brainstem regulate muscle tone and orient your body with respect to gravity and spatial information from your senses. When you walk, shift your weight, or turn your head, brainstem circuits make constant adjustments to maintain your center of gravity over your base of support.

The vestibular nuclei receive information from the inner ear about head position and movement. They send rapid signals to spinal cord motor neurons to correct any postural instability. This system works so quickly that you’re usually unaware of these adjustments—your brain automatically compensates when you stumble or lose balance.

The reticular formation, a network of neurons scattered throughout the brainstem, coordinates postural adjustments during voluntary movements. Even simple actions like reaching forward require anticipatory postural changes. Before you extend your arm, your brainstem activates muscles in your trunk and legs to shift your weight and maintain stability.

The pedunculopontine nucleus area appears particularly critical for postural control. Studies show that smaller brainstem volume, especially in this region, predicts larger center-of-pressure deviations and higher odds of balance loss. The brainstem mediates age-related effects on postural control, underscoring its fundamental role throughout life.

How These Regions Work Together

Movement control emerges from the coordinated activity of all these brain regions operating in parallel and hierarchical loops. The process typically follows this sequence:

Motor planning begins in association cortex areas, particularly in the parietal and prefrontal regions. These areas integrate sensory information about your environment and body position with your goals and intentions. This planning information flows to the premotor and supplementary motor areas.

The basal ganglia and cerebellum receive copies of these motor plans and send modulatory signals back through the thalamus. The basal ganglia select which movement program to execute and suppress competing actions. The cerebellum predicts the sensory consequences of the planned movement and prepares corrective signals.

When the plan is ready, the primary motor cortex initiates the movement by sending signals down the corticospinal tract. Simultaneously, the brainstem receives commands to make anticipatory postural adjustments.

As movement unfolds, sensory feedback streams back to the brain. The cerebellum compares actual movement with intended movement and sends corrections. The basal ganglia monitor performance and adjust the vigor and speed of actions. The brainstem continuously adjusts posture to maintain stability.

This entire process happens in milliseconds, mostly outside conscious awareness. The remarkable coordination between these brain regions allows you to perform complex motor tasks—typing on a keyboard, playing sports, or simply walking—with apparent ease.

What Happens When These Systems Fail

Damage to different motor areas produces distinct patterns of impairment, revealing each region’s unique contribution.

Lesions to the primary motor cortex cause weakness or paralysis on the opposite side of the body. The specific body part affected depends on where the damage occurs. A stroke affecting the hand area of the motor cortex impairs finger movements while leaving other body parts unaffected. Recovery is possible through neuroplasticity, as undamaged areas can partially take over lost functions.

Basal ganglia disorders create striking movement problems. Parkinson’s disease, caused by dopamine neuron loss in the substantia nigra, produces bradykinesia, rigidity, and resting tremor. Patients struggle to initiate movements and move very slowly. Huntington’s disease, involving striatal neuron loss, causes the opposite problem—involuntary, uncontrollable movements called chorea.

Cerebellar damage doesn’t cause paralysis but severely disrupts coordination. Patients walk with a wide-based, staggering gait. Their speech becomes slurred and syllables separate from each other. Reaching for objects becomes imprecise, with excessive corrections. They can’t perform smooth, alternating movements like rapidly turning their hand palm-up and palm-down.

Brainstem lesions affect posture and balance. Depending on the location, patients may have difficulty maintaining upright posture, experience vertigo, or show abnormal muscle tone. Because the brainstem also controls vital functions like breathing and heart rate, damage can be life-threatening.

The Role of Learning and Practice

Your brain’s motor systems are remarkably plastic. Practice doesn’t just strengthen muscles—it fundamentally reorganizes neural circuits controlling movement.

When you learn a new skill, several changes occur simultaneously. The primary motor cortex expands the representation of body parts involved in the practiced movement. Professional musicians, for instance, have enlarged cortical areas controlling their fingers compared to non-musicians.

The cerebellum refines motor commands through error-based learning. Each time you perform a movement, the cerebellum detects discrepancies between intention and execution, then adjusts future commands. With repetition, movements become more accurate and require less conscious attention.

The basal ganglia contribute to habit formation. Initially unfamiliar movement sequences require significant cognitive effort. But as you practice, the basal ganglia gradually take over control, allowing actions to become automatic. This explains why experienced drivers can navigate familiar routes while thinking about other things.

Neuroplasticity enables recovery after brain injury. When stroke damages motor cortex areas, intensive rehabilitation within the optimal time window can promote rewiring. Undamaged cortical regions form new connections to partially compensate for lost functions. The earlier and more intensive the rehabilitation, the better the recovery potential.

Frequently Asked Questions

What is the difference between the motor cortex and motor neurons?

The motor cortex is a brain region that plans and initiates voluntary movements, located in the frontal lobe. Motor neurons are the actual nerve cells that directly stimulate muscles to contract. Upper motor neurons reside in the brain and send signals down, while lower motor neurons in the spinal cord directly connect to muscles. The motor cortex contains upper motor neurons that control lower motor neurons.

Can you control movement without the cerebellum?

Yes, but movement becomes uncoordinated and imprecise. The cerebellum doesn’t initiate movement—other brain regions do that. However, without the cerebellum, you lose the ability to perform smooth, accurate movements. Actions become jerky, with overshooting or undershooting of targets. Balance deteriorates, and motor learning becomes severely impaired.

Why does the left brain control the right side of the body?

Most motor pathways cross over at the base of the brainstem in a structure called the pyramidal decussation. About 90% of corticospinal tract fibers cross to the opposite side, which is why stroke affecting the left motor cortex causes weakness on the right side of the body. The evolutionary reason for this crossing remains debated, but it creates the contralateral organization we observe.

How does the brain learn new movements so quickly?

The brain employs multiple learning mechanisms simultaneously. The motor cortex rapidly adjusts through synaptic plasticity, strengthening connections used during successful movements. The cerebellum provides error-based learning, comparing intended with actual movements and making corrections. The basal ganglia encode action selection patterns. Together, these systems allow relatively rapid skill acquisition, though true expertise requires extensive practice.

Brain movement control exemplifies biological complexity at its finest. Multiple specialized regions contribute unique functions, yet they operate as a unified system. The motor cortex provides direct control, the basal ganglia select appropriate actions, the cerebellum ensures coordination, and the brainstem maintains postural stability. Understanding these systems helps explain both normal motor abilities and the diverse movement disorders that arise when specific components fail. While much remains to be discovered about the detailed mechanisms, the broad architecture of the motor control system is now well established through decades of clinical observations, anatomical studies, and neurophysiological research.

Sources:

1. Johns Hopkins Medicine – Brain Anatomy and How the Brain Works (April 2025)
2. NCBI Bookshelf – Neural Centers Responsible for Movement
3. StatPearls – Physiology, Motor Cortical (June 2024)
4. Frontiers in Systems Neuroscience – Basal Ganglia for Beginners (July 2023)
5. Annual Review of Neuroscience – Cerebellar Functions Beyond Movement and Learning (August 2024)
6. NCBI – Functional Neuroanatomy for Posture and Gait Control
7. Nature Communications – Reward Signals in the Motor Cortex (February 2025)
8. Simply Psychology – Motor Cortex: Function and Location (May 2025)