Restoring Communication

Technologies to Support Speech

Losing the ability to speak can make it difficult to express yourself. Many things can damage the parts of the brain and body that work together to produce speech. Researchers are testing new tools to bypass the damage and restore communication.

Speech is a complicated process. Your brain must turn thoughts into words by firing electrical signals along nerve pathways to the muscles of the vocal tract. Those signals tell your lips, jaw, tongue, voice box, and lungs how to move together to produce sound.

“Talking uses almost 100 muscles,” says Dr. Sergey Stavisky, a neural engineer at the University of California, Davis. “If the pathways from the brain to those muscles are weak or fully blocked, a person can’t speak.”

Several tools can help people who have lost the ability to speak. A new type of system called a brain-computer interface, or BCI, reads signals from the brain and sends them to a computer. The computer then turns those signals into text, a spoken voice, or even movement on a screen. These technologies are helping some people communicate in new ways.

Addressing Speech Loss

There are many conditions that can impact your ability to speak. Amyotrophic lateral sclerosis (ALS) is a progressive disease that weakens muscles and eventually leads to paralysis. Parkinson’s disease is a brain disorder that causes slowed movements, tremors, and stiff muscles.

Other conditions like brain tumors, seizures, strokes, and traumatic brain injuries can affect the parts of the brain we use for speech. Damage to different parts of the brain can lead to different speech issues. Aphasia is a condition in which a person has trouble using or understanding words. Apraxia is when you have difficulty moving your mouth and tongue to say words even when you know what you want to say.

“Speech-language therapists play a key role for people with conditions like aphasia or apraxia, which make it hard to recall words or plan the sounds of speech,” says Dr. Matthew Leonard, a neuroscientist at the University of California, San Francisco. “Through practice and games, therapists help people rebuild word skills and find new ways to share their message.”

There are several tools available to help people who can’t speak. Letter boards are one of the oldest tools. A helper points to letters one by one on a printed board, and the person nods at the right one to spell words. It works without any power or screens, but it is slow and needs a partner who knows the system.

Eye trackers use a small camera that follows the person’s eyes as they look at letters or pictures on a screen. When they hold their gaze on a choice, the computer picks it up. Eye trackers let people type on their own, but they can be tiring to use for long talks.

A head switch is a button that a person taps with their head to pick letters on a screen. A sip-and-puff device lets a person control a computer by breathing in or out through a straw-like tube. Both give people with limited movement a way to spell words.

But the traditional options may not be helpful for people with certain physical limitations. That’s where BCIs can offer an alternative way to communicate.

Bypassing the Body

BCIs let people control computers, robots, or other devices using brain signals. “We would not have been able to create our first successful BCI without the decade’s worth of deep investigation into how the brain works,” says Dr. Eddie Chang, a neurosurgeon at the University of California, San Francisco. Research from Chang’s lab led to the first implantable BCI that was able to decode speech.

Some BCIs sit on the brain’s surface. Others use tiny electrodes that go just under the surface. Both can detect when the brain tries to speak, even when the mouth cannot move. Currently, both of these BCIs require brain surgery and must be connected to a computer through a small port in the skull. Researchers are also studying BCIs that can be implanted via a blood vessel of the brain and used wirelessly.

Other brain-signal technologies do not require an implant. Devices called EEG headsets can be worn as headbands or caps. They can pick up brain signals and decode simple speech patterns, but they cannot translate smooth, ongoing language.

“The technology used to create BCIs has advanced quickly over the last five years,” says Chang.

Stavisky’s team has already developed a BCI that connects to a home computer to restore speech for people with vocal tract paralysis.

But advances in technology are only part of the challenge. To turn brain activity into speech, researchers need to understand which parts of the brain are involved and to determine where to place the BCIs.

Leonard’s team researches how each person’s brain turns speech sounds into words to help guide BCI development and placement.

“We used to think that we could just use anatomy to find where speech and language is processed in the brain, but it turns out that there is a lot of variation from person to person,” says Dr. Jaimie Henderson, a neurosurgeon at Stanford University. For a BCI to work well, it needs to detect strong signals from specific areas of the brain.

A recent focus for Henderson’s team has been using functional MRIs to study where to place BCI sensors for the clearest brain signal recordings. A functional MRI allows doctors to watch a person’s brain while it’s at work. The images can show where the brain processes speech and language. This helps doctors determine where to place the BCI sensors.

What’s Next?

While EEG devices are currently available commercially, right now, implanted speech BCIs are available only through clinical trials. People who might be eligible to participate include those with ALS, lasting stroke symptoms, a spinal cord injury, or paralysis. To search for a clinical trial, visit clinicaltrials.gov.

“Our team and others have shown that people can use BCI devices on a day-to-day basis to restore communication,” Henderson says. He and other researchers hope that after a few more years of testing, these devices will be more accessible to those who need them.

If you have a loved one who has lost their ability to speak, there are ways you can help improve communication. See the Wise Choices box for tips.