The motor cortex is an area in the frontal lobe that plans and executes voluntary movements by working with other brain areas and the spinal cord.
It can be divided into two main regions: the primary motor cortex, which initiates movements, and the nonprimary motor cortex, which handles movement planning and selection.
Each hemisphere controls muscles on the opposite side of the body.
Key Takeaways
- Motor cortex = brain region that controls voluntary movement.
- Located in the frontal lobe, with each side of the brain controlling the opposite side of the body.
- Includes the primary motor cortex (executes movement) and nonprimary areas (plan and coordinate).
- The motor homunculus shows which body parts get the most brain space—hands and face take priority.
- Damage can affect strength and coordination, but the brain can relearn through neuroplasticity and therapy.
Where Is the Motor Cortex Located?
The motor cortex sits in the frontal lobe of your brain, just in front of a groove called the central sulcus.
It includes two main areas:
- Primary motor cortex (M1): Located in the precentral gyrus, this area sends movement commands directly to your muscles.
- Nonprimary motor cortex: Located just in front of M1, this region helps with planning and preparing movements before they happen.
Each side of the motor cortex controls the opposite side of your body. So, the left hemisphere controls the right side of your body, and vice versa.
Key Functions of the Motor Cortex
The motor cortex does much more than just send movement signals. It’s involved in:
- Starting and controlling voluntary movement
- Planning movement sequences (like dancing or typing)
- Coordinating different muscle groups
- Using sensory feedback to fine-tune motion
- Learning and refining motor skills through practice
Primary Motor Cortex Functions
The primary motor cortex is like the brain’s command center for movement. It uses special nerve cells called pyramidal neurons to send instructions from the brain to the muscles.
These instructions travel along two major pathways:
- Corticospinal tract: Sends signals to your spinal cord to move your body.
- Corticobulbar tract: Sends signals to your brainstem to control facial, jaw, and tongue movements.
This part of the brain doesn’t control single muscles in isolation—it coordinates complex motions involving multiple muscles at once.
Nonprimary Motor Cortex
The nonprimary motor cortex includes two key regions: the premotor cortex and the supplementary motor area (SMA).
Premotor Cortex: Imitation and Action Planning
This area helps you choose the right movement for a situation, especially in response to what you see.
It works with the cerebellum to plan motions and is home to mirror neurons, which fire both when you do something and when you watch someone else do it. This helps you learn by observing others.
Supplementary Motor Area: Learning and Fine-Tuning
The SMA handles more complex actions, like learning a new instrument or adjusting your movement in real time.
It plays a big role in coordinating sequences of movements and adjusting based on sensory feedback.
Motor Homunculus
Inside your motor cortex is a map of your body, known as the motor homunculus. It shows how different areas of the cortex control different body parts.
- Body parts with fine motor control—like the hands, lips, and face—take up more space on this map.
- Larger body parts that need less precision—like the trunk or thighs—take up less space.
This explains why you can do delicate tasks with your fingers but not with your knees.
Motor Vs. Sensory Homunculus
The motor homunculus is not to be confused with sensory homunculus, which is a sensory representation in the somatosensory cortex in the postcentral gyrus.
This homunculus represents how body parts feel, whereas the motor homunculus represents how body parts move.
The regions of the body representations on the sensory homunculus differ slightly from that of the motor counterpart as some areas of the body are more sensitive to sensations rather than movements, such as the head.
What Happens When the Motor Cortex Is Damaged?
Damage to the motor cortex—often from a stroke or brain injury—can cause a range of motor problems, depending on the area and severity.
Common Symptoms:
- Weakness on the opposite side of the body
- Poor coordination and motor control
- Trouble with fine motor tasks (like buttoning a shirt)
- Muscle stiffness or spasticity
- Overactive reflexes (hyperreflexia)
- Fatigue or decreased movement endurance
Can the Brain Recover?
Yes—thanks to a powerful ability called neuroplasticity, your brain can sometimes reorganize and assign motor functions to other areas.
With the right physical or occupational therapy, many people regain movement skills over time through repeated practice and retraining.
References
Purves, D., Augustine, G., Fitzpatrick, D., Katz, L., LaMantia, A., McNamara, J., & Williams, S. (2001). Neuroscience 2nd edition. Sunderland (ma) sinauer associates. Types of Eye Movements and Their Functions.
Neuroscientifically Challenged (2015, October 23). Know Your Brain: Motor Cortex. https://www.neuroscientificallychallenged.com/blog/know-your-brain-motor-cortex
Knierim, J. (2020, October 20). Chapter 3: Motor Cortex. Neuroscience Online. https://nba.uth.tmc.edu/neuroscience/m/s3/chapter03.html
Flint Rehab (2020, November 19). Primary Motor Cortex Damage: Definition, Symptoms, and Treatment. https://www.flintrehab.com/primary-motor-cortex-damage/
