Edward F. Chang

Edward Chang, MD, has devoted his career to unraveling one of neuroscience’s most complex and uniquely human puzzles: how the brain enables us to understand and produce words. He first encountered this mystery as a medical student at UC San Francisco. “When we got to the lessons on language, it dawned on me that we know so little about how it works, especially compared to how much we understand about breathing or circulation,” he recalls. “It just seemed like a magical and profound mystery.”

That mystery became a driving challenge. Recognizing that speech is a uniquely human function—and thus hard to study in animal models—Chang pursued training that would allow him to bridge clinical neurosurgery and basic neuroscience. As a medical student, he completed a research fellowship with renowned neuroscientist Michael Merzenich, PhD, a pioneer in cortical plasticity and brain mapping. This early exposure laid the foundation for a career at the intersection of surgery, science, and technology.

Chang remained at UCSF for his neurosurgical residency, specializing in functional neurosurgery, including the treatment of epilepsy and brain tumors. “I was drawn to neurosurgery for three reasons,” he says. “First, for the deep relationship with patients facing serious neurological conditions. Second, for the technical precision required in operating on delicate neural structures. And third, because of the unmatched opportunity it gave me to explore the brain and contribute to understanding what makes us human.”

Mentored by leaders such as Robert Knight, MD, Mitchel S. Berger, MD, and Nicholas Barbaro, MD, Chang developed both the clinical skills of neurosurgery and the foundation for an innovative research program. This rare dual expertise has allowed him to make scientific contributions that few clinician-researchers are positioned to achieve.

A central pillar of Chang’s work is functional brain mapping, using high-density electrode arrays to study how different areas of the brain support distinct functions. “Brain mapping helps us understand not only where language functions reside in the brain, but how they work,” he explains.

Chang and his team mapped key aspects of both speech perception and speech production—including how the brain encodes vowels and consonants, vocal pitch, syllable rhythm, and background noise filtering. They also identified the motor areas that govern vocal tract movements, including the larynx, tongue, and lips, and the neural circuits involved in planning and sequencing speech.

These insights led to a transformative clinical application: the development of a speech neuroprosthesis. In a groundbreaking clinical trial, Chang’s group created a device that records brain signals from speech motor areas and decodes them into words. “We built a system that could translate neural activity into language,” he says.

The device uses surgically implanted electrodes to capture speech-related brain signals. When patients attempt to speak, the system detects specific patterns of electrical activity associated with intended words and translates them into intelligible sentences. In 2021, his team restored communication for a patient who had been unable to speak for 15 years following a brainstem stroke. Subsequent advances have improved speech synthesis speed and enabled avatar-based communication, and other research groups have since replicated key elements of the approach.

“What made this possible was a decade of basic science aimed at decoding the neural representation of words,” Chang says. “We identified the building blocks—consonants, vowels, prosody—and how they’re encoded in the brain.” Advances in artificial intelligence played a critical role, enabling the system to filter out noise and accurately decode complex patterns of brain activity.

For patients with paralysis due to stroke, ALS, or other conditions, this neurotechnology opens the door to restored communication and human connection—using only their brain signals.

Looking ahead, Chang is focused on pushing the limits of brain mapping resolution. “For the last 15 years, we’ve been using electrodes on the brain’s surface at the millimeter scale,” he says. “Now, we have tools that allow us to record from thousands of individual neurons simultaneously. We’re entering a new era of neuroscience—one that allows us to study the brain at an unprecedented level of detail.”