Suffering from a stroke often means impaired speech for the rest of that patient’s life.
But could there be a way to help restore speech by switching on a part of the brain that’s normally not involved in speech?
For right-handed people, speech production is usually on the left side of the brain.
For left-handed people, it’s often on the right.
But it’s not that simple, says psychologist Gesa Hartwigsen from Kiel University.
In her study published in PNAS, she explores which brain areas really control speech and how they work together.
The goal is to help patients with speech problems or aphasia after a stroke.
Comprehending and Speaking
Hartwigsen and her team started by studying speech production in healthy volunteers.
They asked right-handed participants to listen to and repeat words.
These were pseudo words, like “biufo,” which don’t have any meaning in German.
Because the words had no meaning, no brain areas related to understanding meaning were activated.
The team used a combination of fMRI (funtional MRI) and TMS (transcranial magnetic stimulation) to see what was happening in the brain during the test.
As expected, the left hemisphere was active during speech production.
The right hemisphere did not normally contribute to language in healthy brains.
This confirmed what scientists had assumed: The right hemisphere was usually not involved in speech production.
Interfering and Measuring
Next, the team simulated a stroke-like disruption in Broca’s area, the speech production region in the left hemisphere.
They used a harmless magnetic pulse from a coil, which temporarily interrupted the area for 30 to 45 minutes.
During this time, these right-handed participants repeated the pseudo words again.
Left hemisphere activity was suppressed, and some people took longer to repeat the words.
But the team noticed something unexpected: The right hemisphere became more active.
The more the right hemisphere activated, the faster the participants could complete the speech tests.
The right hemisphere seemed to help compensate for the disruption in the left hemisphere.
This suggests the right hemisphere can actively support speech production, even though it was previously thought not to.
Results and Implications
The study shows that both hemispheres can interact during speech.
After a stroke, the right hemisphere could potentially be stimulated to help recovery.
Timing would be critical. Early after a stroke, supporting the right hemisphere could be helpful.
Later, when the left hemisphere is ready to take over again, it might be better to focus stimulation there instead.
Correct timing could be key to effective speech recovery.
What are the next steps?
Hartwigsen is now working with colleagues and doctoral students on a follow-up study.
They want to learn more about how the hemispheres collaborate and the best timing for helping stroke patients recover speech.
Her research is relatively new in cognitive neuroscience.
But she is optimistic it could lead to practical therapies within 10 to 15 years.
