ROCHESTER, Minn. — Mayo Clinic researchers have identified a hidden "movement map" deep within the brain — a discovery that could help surgeons reduce side effects from epilepsy procedures and guide future treatments for speech and movement disorders.
In a study published Feb. 18 in the Proceedings of the National Academy of Sciences , the team reports that a small, buried brain region called the insula contains its own organized map of the body. Distinct areas within the insula are linked to movement of the hands, feet, and tongue.
The finding has immediate relevance for epilepsy care. Surgeons sometimes operate in or near the insula to treat seizures, and up to 30% of patients can experience temporary problems with speech, swallowing or hand movement afterward. Until now, doctors did not have detailed maps showing exactly where those functions are located in this deep brain region.
"If we can identify where hand and speech functions live in each patient, we can better anticipate — and potentially avoid — those deficits," says Panos Kerezoudis, M.D., a Mayo Clinic neurosurgery resident and lead author of the study. "This gives us a practical roadmap."
The insula sits several centimeters beneath the brain's surface, hidden under other lobes, which has made it difficult to study with traditional techniques.
"For a long time, people thought this region was generally active during many tasks — more of an integrator than a structured map," says Dr. Kerezoudis. "We wanted to know whether it follows the same organized layout we see in the main motor cortex, or if it responds the same way no matter what you move."
To answer that question, researchers in the Cybernetics and Motor Physiology Lab at Mayo studied 18 patients with medically refractory epilepsy who had thin recording electrodes placed deep in their brains as part of their clinical care.
While hospitalized, patients performed simple movements such as opening and closing their hand, moving their tongue, or flexing their foot. The electrodes recorded electrical activity in both the insula and the primary motor cortex, the brain's main movement center, with millisecond precision.
The results showed clear organization: hand movements activated one area of the insula, tongue movements another and foot movements yet another, though less prominently.
"We found distinct body-part representation in this deep structure," says Dr. Kerezoudis. "It is not random. There is order."
The timing of activity was also revealing. The primary motor cortex became active first, followed by the insula, and then movement occurred.
"This shows that the insula is not simply reacting after we move," says Kai Miller, M.D., Ph.D. , a Mayo Clinic neurosurgeon and senior author of the study. "This discovery expands our understanding of how movement is supported by a distributed brain network whose parts are more tightly integrated than we previously thought. By mapping it carefully, we can make brain surgery and neuromodulation safer, more precise, and beneficial for more people."
In a subset of patients, researchers delivered brief, safe electrical pulses to test how the regions communicate. Stimulating a hand-related area in the motor cortex triggered a response in the matching area of the insula, and the same pattern held for tongue regions.
"The connections respect the body map — hand connects to hand, tongue to tongue," says Dr. Kerezoudis. "That strengthens the case that this is an organized network."
Clinically, the findings could help neurologists better interpret seizure symptoms, such as hand contractions or facial movements, and refine electrode placement during epilepsy evaluations. Surgeons may also use individualized maps to plan procedures more precisely.
Beyond epilepsy, the work may inform future therapies for stroke survivors with speech or hand movement difficulties. If movement relies on a network that includes both the primary motor cortex and the insula, treatments such as targeted brain stimulation may need to address both areas.
The study supports Mayo Clinic's Bioelectronic Neuromodulation Innovation to Cure (BIONIC) initiative by using advanced brain-recording technology to translate scientific discoveries into practical care strategies. It also aligns with Pre-cure, which focuses on anticipating and preventing complications before they occur — such as identifying critical movement areas before surgery rather than reacting to deficits afterward.
For a complete list of authors, disclosures and funding, review the study .
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Proceedings of the National Academy of Sciences
The human insula encodes somatotopic representation of motor execution with an effector-specific connectome map to primary motor cortex
18-Feb-2026