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.

The study was published in the journal Nature.