Study upends decades-old map of how the brain controls movement

Amazing stuff!

Stanford University still suffers from the silly season? Only today they feature an article written back in mid June 2026!

"In brief

• A study of the long-held motor homunculus model reveals a more complex organization of the motor cortex that affects body movement control.
• Research shows areas in the motor cortex encode information for multiple body parts, suggesting broader relationships than previously understood.
• The findings could enhance brain-computer interface development for paralysis patients, enabling more versatile control with fewer implants.

..."

From the abstract:

"Understanding how the body is represented in the motor cortex is key to understanding how the brain controls movement.

Although the motor cortex has been mapped in animal models at a fine scale, characterization in humans remains primarily limited to low-resolution recording and stimulation techniques.

Here we created a comprehensive map of the human motor cortex at single-neuron resolution, spanning microelectrode array recordings from 20 arrays across 8 individuals with paralysis from spinal cord injury, amyotrophic lateral sclerosis or brainstem stroke, all enrolled in brain–computer interface clinical trials.

These arrays broadly sample the crown of the precentral gyrus (PCG; thought to be composed largely of the premotor cortex (Brodmann area 6)).

We found that body parts were highly intermixed, such that the entire body was represented in all sampled locations of the PCG, although the relative strength of body parts was roughly consistent with the motor homunculus.

We also found two speech-preferential areas with a broadly tuned, orofacial-dominant area in between them.

Throughout the PCG, movement representations of the four limbs were interlinked, with homologous movements of different limbs (for example, toe curl and hand close) having correlated representations. 

These data provide evidence consistent with an intermixed, interrelated and behaviour-centred organization of the motor cortex. The resulting map also provides important targeting information for brain–computer interfaces that seek to restore motor function."

Stanford University

Study upends decades-old map of how the brain controls movement "New research challenging a model long taught in neuroscience textbooks could lead to more powerful brain-computer interfaces for people living with paralysis."

It’s time to revamp the motor homunculus "An update to the 89-year-old model shows that the brain’s motor cortex isn’t as neatly organized as previously thought. For almost a century, budding neuroscientists have been taught that the headband-like strip of brain tissue over our ears that controls our movements, called the motor cortex, contains an orderly map of our bodies.

Brain cells concerned with moving each body part – from the tips of our toes to the tips of our fingers – are all laid out in sequence, as well as a large zone dedicated to our fabulously expressive faces and speech muscles. That’s the textbook account, anyway."

A mosaic of whole-body representations on the human precentral gyrus (open access)

A map of the motor cortex highlighting regions tuned more for speech-related movements (red) and arm movements (blue-green) and a particularly broadly tuned region (purple).

Fig. 1: Sampling the length of the PCG to assess whole-body movement representation.

Fig. 5: A compositional neural code throughout the PCG that links all four limbs together.