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Journalism of Courage
Scientists have developed a brain-computer interface (BCI) — a device that allows the human brain to communicate with external software or hardware — which works only when the user thinks of a preset password.
The findings were detailed in a study, ‘Inner speech in motor cortex and implications for speech neuroprostheses’, published in the journal Cell on August 14. The new system was developed by researchers based at Stanford University (the United States).
Sarah Wandelt, a neural engineer at the Feinstein Institutes for Medical Research (the US), who was not part of the work, told Nature that the breakthrough was a “technically impressive and meaningful step” towards developing BCI devices that accurately decode internal speech. She also said that such devices would help protect the privacy of the users.
Here is a look at how scientists built a password-protected BCI.
But first, why are brain-computer interfaces significant?
BCIs allow the user to control an application or a device using only their mind. Usually, when someone wants to interact with an application — let’s say, they want to switch on a lamp — they first have to decide what they want to do, then they coordinate and use the muscles in their arms, legs or feet to perform the action — like pressing the lamp’s on/off switch with their fingers. Then, the device — in this case, the lamp — responds to the action.
What BCIs do is help skip the second step of coordinating and using the muscles to perform an action. Instead, they use a computer to identify the desired action and then control the device directly.
This is the reason why BCIs have emerged as promising tools for people with severe physical disabilities. They are also being used to restore speech in people who have limited reliable control over their muscles.
How was a password-protected BCI developed?
The researchers involved in the study focused on “internal-speech” BCIs, which translate brain signals into text or audio. While these types of devices do not require users to speak out loud, there is always a risk that they could accidentally decode sentences users never intended to say.
To resolve this issue, the researchers first “analysed brain signals collected by microelectrodes placed in the motor cortex — the region involved in voluntary movements — of four participants,” according to a report by the journal Nature. All of these participants had trouble speaking and were asked to either try to say a set of words or imagine saying them.
The researchers then analysed the recordings of participants’ brain activity. This helped them discover that attempted and internal speech originated in the same brain region and generated similar neural signals, but those associated with internal speech were weaker.
This data was used to train artificial intelligence models, which helped BCIs to interpret sentences imagined by the participants after they were asked to think of specific phrases. The devices correctly interpreted 74% of the imagined sentences.
To ensure that the BCIs do not decode sentences that users do not intend to utter, the researchers added a password to the system, allowing users to control when decoding began.
“When a participant imagined the password ‘Chitty-Chitty-Bang-Bang’ (the name of an English-language children’s novel), the BCI recognised it with an accuracy of more than 98%,” the Nature report said.
(With inputs from Nature)
