How Does Your Brain Control Your Body?
Healthy people move all day without thinking about it. How does that happen?
Moving your arm, hand, and mouth to brush your teeth seems to happen without any mental effort. Your brain, muscles, and eyes always talk to each other. This helps you move on purpose and react without thinking, like pulling your hand away from a hot stove.
Many of our bodily functions, like breathing, blinking, and the beating of our hearts, run on autopilot. In contrast, other coordinated movements run on muscle memory (like standing up and walking across a room).
Newer, complex actions demand more from your brain and body, such as:
- learning to skateboard
- play the piano
- roll your Rs to speak Spanish
- pour olive oil with one hand while whisking it with the other
Once a new skill is learned, you can usually do it easily. This is true as long as your body can keep up.
James David Guest, M.D., PhD., FAANS, is a professor of neurological surgery with the University of Miami’s Miller School of Medicine and a scientific faculty member with The Miami Project to Cure Paralysis, a Center of Excellence at the Miller School. Dr. Guest’s research and clinical practice are focused on helping people regain their lost functions or mobility following spinal cord or brain injury.
Today, he is helping us understand the relationship and communication between the brain and the body. This system helps us move easily and purposefully in the world.
How does a thought become a coordinated movement?
“The transformation from thought to movement involves multiple parallel pathways that use the brain, spinal cord, muscles, and sensory mechanisms,” Dr. Guest says.
A voluntary movement starts with a decision — like wanting to fold a piece of paper. That intention is processed in the brain’s premotor and supplementary motor areas. These regions plan which muscles need to move and in what order. The command then travels through the corticospinal tract — a pathway of nerve fibers connecting the brain to the spinal cord — then it’s sent to the nerves and muscles that perform the action.
Some parts of the brain’s premotor cortex help you respond to space around you, like figuring out how far to move your leg when taking a step. Other areas focus on the details of an object or surface, such as how gently to hold something fragile or how to adjust your step on uneven ground. Many of these movements happen automatically, with the spinal cord making quick adjustments without you needing to think about it.
The brain’s cortex doesn’t work alone.
Signals from the brain travel down to the spinal cord, where they reach special nerve cells called interneurons that help control walking. These cells act like pattern generators, says Dr. Guest. They create the rhythmic, repeated movements needed for walking and adjust as needed, such as shifting weight between your left and right legs.
Other brain pathways, like the reticulospinal and vestibulospinal tracts, help with posture and whole-body coordination. They keep the body stable so that more precise pathways, like the corticospinal tract, can handle detailed movements — such as using your fingers to play the violin.
The brain’s cerebellum predicts and corrects movements in real time.
“The cerebellum compares your intended movement with incoming sensory feedback and generates error signals. It serves a regulatory and monitoring function. Your movements are responsive to changing visuals, sounds, the sense of physical contact, and joint positions, as well as warning signals like pain,” he says. “These predictive loops allow you to make smooth movements, even when sensory feedback is delayed. The cerebellum has already calculated where your limb should be.”
What happens when your brain misinterprets what you see and feel?
Have you ever looked at your reflection in a mirror with the help of a second mirror? Maybe you’ve done this so you can see the back of your head. The effect flips your reflection, which can be disorienting. You try to comb your hair, only to find your arm reaching for the opposite side of your head. When you try to correct yourself, you may reach even farther in the wrong direction.
What’s going on when this happens?
Dr. Guest says that this experience reveals the essential relationship between your brain’s sensory inputs (sight, sound, and your perception of where your body is in space, called proprioception) and your body’s balance and motor systems. These all work together so you can maintain a coherent sense of your body’s position.
“Normal spatial coordination depends on reference frames that are computed by the brain’s posterior parietal cortex,” he says. “This region of the brain integrates predictive data from your eyes (retinas) and your balance system (inner ear) and combines them with muscle and joint data to create a sense of your body in space.”
When what you see conflicts with reality — like seeing your reflection reversed in a mirror — “your brain must rapidly choose which input to trust,” Dr. Guest says.
“Mirror reversal creates a conflict between visual feedback (your hand moving right in the mirror) and proprioceptive feedback (your hand actually moving left). The parietal cortex must perform a rapid coordinate transformation, essentially applying a mental rotation.”
This increased demand on your brain is easy to detect, as it takes you longer than usual to react and correct your movements. If your brain was in a functional MRI scanner at the time, the imaging would show increased activity in the parietal lobe.
Sensory illusions show how your vision can change how you feel about your body. This includes your posture, position, and place in space.
“When someone watches a rubber hand being stroked synchronously with their hidden real hand, they begin to ‘feel’ the stroking on the rubber hand and misjudge their actual hand position by several centimeters. This illusion engages the brain’s premotor and parietal cortex, areas that maintain body schema,” Dr. Guest says.
With another sensory illusion, a person wears prisms that shift their visual field.
“Initially, they miss the target. But, within 20 to 30 attempts, their cerebellum adjusts the mapping between visual targets and motor commands,” he says. “Remarkably, this recalibration produces aftereffects. When the prisms are removed, the person will initially miss the target in the opposite direction until their brain readapts to normal vision.”
Improve your bodily awareness and coordination with practice and sleep.
We have all experienced that with practice, we can learn complex motor skills that initially seem very challenging, like riding a bicycle. Once you learn a skill like this, you can easily pick it up again, even decades later, without having to learn it all over again.
How does this form of muscle memory work?
“Early attempts at learning a new skill rely heavily on conscious control and visual guidance. With repetition, your nervous system builds statistical expectations about how your muscles, joints, and sensory feedback behave. This early practice heavily engages your brain’s prefrontal and parietal areas, with conscious attention to every detail of the movement,” Dr. Guest says.
The cerebellum quickly fine-tunes your timing and strength using special cells that change based on your experiences. When you make a mistake, signals from climbing fibers help adjust these connections within minutes. Additionally, the circuits in your spinal cord learn to make your movements more efficient over time.
“With repeated practice, your brain creates memory circuits that act like predictive models. While you sleep, these motor memories transfer from cortical areas and are stored as loops in the brain’s cerebellum and basal ganglia,” he says. “This is why skilled movements consolidate and become ‘chunked’ together. Individual elements merge into fluid sequences that you can later execute as a continuous unit of movement.”
This learning changes the structure of your brain.
“Neuroplastic changes involve the formation and strengthening of new connections through the creation of new or strengthened synapses. Synapses are where the electrical signals release neurochemicals,” Dr. Guest says.
“With extensive practice, the cerebellum’s predictive maps become more accurate, reducing the need for conscious error correction. The brain’s models can accurately frame sensory inputs to guide the body’s actions. This is why experts can perform complex movements with minimal visual feedback.”
“Studies of musicians show that their brains have expanded cortical representations of their fingers, with increased gray matter density in areas corresponding to their trained movements. Expert pianists show more precise somatosensory discrimination of finger positions than piano novices,” he says. “Another example is that an experienced mechanic can make adjustments using their hand when it’s inside a tight box. This means they’ve essentially increased the resolution of their body maps.
“With extensive practice, you can ‘see’ in your mind an object by using touch perception, based on your prior experience. We can also refer to this ability as ‘intuitive’ because the practice in other situations provides a general prediction that can be adapted to slightly different circumstances,” says Dr. Guest.
How does thinking override muscle memory?
Once you have practiced a set of movements enough, they become automatic. Thinking about the motion instead of acting on instinct can make it hard to do the task without mistakes.
Example: when your fingers can dial your friend’s phone number without any thought. But if you try to consciously select each digit, you can’t even remember the number.
Your muscles and brain store muscle memory.
“In your muscles, muscle memory is a cellular mechanism that describes the capacity of skeletal muscle fibers to respond differently to environmental stimuli in an adaptive manner when those stimuli have been previously encountered,” says Dr. Guest.
“In your brain, muscle memory involves long-term procedural memory circuits in the cerebellum, motor cortex, and basal ganglia.
“Once you have learned a specific, coordinated series of movements, these ‘subcortical’ loops can execute it automatically, with little involvement from the conscious prefrontal cortex. We might call this ‘confidence.’ But, when you overthink, your prefrontal cortex (involved in working memory and executive control) sends top-down signals that compete with your automatic programs — breaking your otherwise good confidence. This can happen with excess anxiety,” Dr. Guest says.
Several mechanisms lead to this type of performance error.
“Mental and verbal-based thinking are processed in different, slower networks than highly practiced automatic movements, which rely on implicit knowledge stored in subcortical structures. Overthinking activates cortical areas that don’t usually participate in the execution of trained movements. These competing thinking signals interfere with the fast, subcortical timing, interrupting them,” he says. “Excessive focus on movement details can reduce the available processing speed for implicit control and interfere with athletic performance.”
While you’re learning a motor skill, your brain experiences increased activity in the cortical regions.
Once you’ve trained yourself to perform this skill without error using muscle memory, the activity in these brain regions is reduced while brain activity increases in the cerebellar and striatal areas.
This reflects the trained movements being ‘offloaded’ to automatic systems, Dr. Guest says.
The Miami Project to Cure Paralysis
The interdependent relationship between different regions of the brain, muscles, eyes, ears, and skin receptors can be interrupted or break down due to musculoskeletal injuries or injuries to the brain and/or spinal cord.
Dr. Guest and his colleagues at The Miami Project to Cure Paralysis use research to advance our understanding and the treatment of such debilitating injuries.
Click here to learn more about The Miami Project’s life-changing work.
Written by Dana Kantrowitz.
Medically reviewed and approved by James David Guest, M.D., PhD., FAANS in November 2025.
Tags: Cognitive motor control, Dr. James David Guest, Motor skill development, Neuroplasticity
