In this file photo a patient is examined during a scan
session at the University Hospital in Liege, Belgium.
We use both sides of our
brain for speech, according to a new study that could rewrite therapies for
those who have lost the ability to speak after a stroke.
“Our findings upend what
has been universally accepted in the scientific community — that we use only
one side of our brains for speech,” said Bijan Pesaran, an associate professor
in New York University’s Centre for Neural Science and the study’s senior
author.
“In addition, now that we
have a firmer understanding of how speech is generated, our work toward finding
remedies for speech afflictions is much better informed,” Pesaran said.
Scientific community has
largely believed that both speech and language are lateralised — that is, we
use only one side of our brains for speech, which involves listening and
speaking, and language, which involves constructing and understanding
sentences.
However, the conclusions
pertaining to speech generally stem from studies that rely on indirect
measurements of brain activity, raising questions about characterising speech
as lateralised.
To address this matter,
the researchers directly examined the connection between speech and the
neurological process.
Specifically, the study
relied on data collected at NYU ECoG, a centre where brain activity is recorded
directly from patients implanted with specialised electrodes placed directly
inside and on the surface of the brain while the patients are performing
sensory and cognitive tasks.
Here, the researchers
examined brain functions of patients suffering from epilepsy by using methods
that coincided with their medical treatment.
The researchers tested the
parts of the brain that were used during speech. Here, the study’s subjects
were asked to repeat two “non-words” — “kig” and “pob.”
Using non-words as a
prompt to gauge neurological activity, the researchers were able to isolate
speech from language.
An analysis of brain
activity as patients engaged in speech tasks showed that both sides of the
brain were used — that is, speech is, in fact, bi-lateral.
“Now that we have greater
insights into the connection between the brain and speech, we can begin to
develop new ways to aid those trying to regain the ability to speak after a
stroke or injuries resulting in brain damage,” said Pesaran.
“With this greater
understanding of the speech process, we can retool rehabilitation methods in
ways that isolate speech recovery and that don’t involve language,” Pesaran
said.
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