Many conditions cause difficulty with speech output, such as autism, stroke, head injury and brain tumors.
Scientists are working on a device that can grab thoughts, that are intended for speech, and display them.
Imagine seeing a fuzzball — that moves and squirms: an eight week old puppy.
You know it’s a puppy; you may even know the breed name: chocolate lab.
But “puppy” and “chocolate lab” are stuck on the tip of your tongue.
This frustrating experience is linked to something called Broca’s aphasia, or expressive aphasia.
It’s a language disorder that makes speaking or writing difficult.
The reason writing is also affected in Broca’s aphasia is because the neurological sequence of thought-intention to speak, to the physical output of speech, is the same neuro-pathway of thought-intention to write, to the physical output of writing — even if it’s block letters with a crayon.
Right now, the main treatment is speech therapy, but researchers at Northwestern University are exploring a new approach: a brain-computer interface, or BCI, to turn brain signals directly into spoken words.
Finding the Right Spot in the Brain
The first challenge is figuring out exactly where in the brain a BCI should listen to decode intended speech.
Imagine the implications this could have for nonverbal autistic people.
Currently, BCIs are mostly used in people with paralysis from ALS or brainstem strokes, who can’t move or speak.
In these cases, devices pick up signals from the frontal lobe.
But Broca’s aphasia usually happens after a stroke or brain tumor that damages the frontal lobe itself — the very area responsible for speech.
This region may also be damaged in a motor vehicle crash or other type of head trauma.
Scientists need to look elsewhere in the brain to help these patients.
New Brain Areas Identified
Northwestern Medicine researchers found for the first time that parts of the temporal and parietal cortices (singular: cortex) — areas outside the frontal lobe — play a role in the intent to speak.
This discovery could eventually make it possible to use BCIs to treat Broca’s aphasia.
Dr. Marc Slutzky, a professor of neurology and neuroscience at Northwestern, explains in the paper that the team showed that these particular regions hold information about an individual’s intent to talk or even say a single word.
It allowed the researchers to detect when someone was about to speak, as opposed to just merely thinking a few words or thinking a phrase that they don’t actually want to verbalize out loud.
These early findings are crucial for designing BCIs that can distinguish between speech production and language comprehension.
It’s important not to decode thoughts that a person wouldn’t want to say out loud.
We all produce thoughts, in the form of words or a voice inside our head, that we’d never want to speak out loud.
How the Study Was Done
The study didn’t involve people with aphasia. Instead, researchers worked with nine patients who had either epilepsy or brain tumors but no language deficits.
Electrical signals were recorded from the surface of the brain using a method called electrocorticography.
For epilepsy patients, electrode arrays were implanted as part of seizure monitoring.
Tumor patients had electrodes placed temporarily during awake brain surgery.
Patients were asked to read words aloud from a screen or remain silent while researchers recorded their brain activity.
What’s Next
The next step is for the researchers to decode exactly what these patients said.
Understanding this will help scientists figure out how to use BCIs to restore speech for people with Broca’s aphasia in the future.
“Broca’s Brain”
Pierre Paul Broca was a 19th century French physician who studied how brain injuries affected speech.
He discovered a small area in the left frontal lobe that controls talking.
Because his research was groundbreaking, scientists named that spot “Broca’s area” in his honor, for the impact it had on neuroscience worldwide.
