Imagine that transform thoughts into audible words: that’s what Stanford researchers did with a new neural implant capable of transforming internal language, that is, the dialogue that happens in our mind without saying it out loud, into words. All this is made possible thanks to a series of microelectrodes implanted in the cerebral cortexwhich are able to interpret the electrical signals produced by a person when he “thinks he is speaking” and translate them in real time in the form of language. Also, to protect cognitive privacy of those who use it, the technology uses an activation system via “mental password”.
How the new brain implant that reads thoughts works: the initial phase
Of all human abilities, verbal communication is perhaps the one that most defines the human being. For this reason, the loss of the ability to produce spoken language due to neurodegenerative diseases or brain trauma it actually becomes the deprivation of a part of oneself. Now, imagine that a technology could directly read the internal language and transform it into audible words, giving them back the ability to communicate. That’s what he managed to do a team from Stanford Universitydeveloping a brain implant capable of decoding neural activity and translating it into language, with an accuracy of up to 74%.
The development ofbrain-computer interface (BCI) it followed a certain progression before arriving at today’s complex functionality. Early in their experiments, associate professor of neurosurgery Frank Willett and his colleagues used the interfaces to help people whose paralysis left them unable to speak. In detail, they were used microelectrodes implanted in the motor cortexthe region of the brain from which the motor neurons responsible for all muscle movements including those of the mouth and tongue originate, aimed at producing a word. When a person tries to speak, gods are produced neural signals which are recorded by the electrode device. These signals are then transmitted via cable to a computer algorithm which translates them into audible speech or cursor movement over computer letters.
To decode neural activity responsible for the word you want to pronounce, researchers use automatic learning or machine learning (i.e. the AI mechanism that allows systems to learn from experience without being explicitly programmed). In short, every word or sound produces one pattern of neural activity slightly different from each other. When a person tries to pronounce different phonemes, the computer records these neural patterns and the machine learning algorithm learns to connect each of them to the corresponding phoneme. When the user tries to speak, the system recognizes the already learned neural patterns corresponding to the phonemes and the computer then assembles them in the correct sequence to form words and sentences.
How does the implant translate the inner language into words
Recently, scientists took another important step: they studied brain signals related to “inner speech” (also called “inner monologue”). The ambition of Frank Willet and Erin Kunz from Stanford University was to be able to decode even words and sentences that did not require muscular effort to produce. They therefore wanted to know whether a BCI system could work based only on the neural activity evoked by imagined speech, rather than on attempts to physically produce speech. This is because, for people with paralysis, attempting to speak can be slow and laborious and, if the paralysis is partial, can produce distracting sounds and difficulty controlling breathing. During the experiment, conducted on four patients who had lost the use of speech due to stroke or motor neuron disease – nerve cells that control voluntary muscles – (such as ALS), participants were asked to imagine words and sentences.
Both the studies of neuroimaging that electrophysiological studies have demonstrated that internal language involves a cortical network similar, although not identical, to that of language physically produced in the motor cortex; so it was thought that the electrodes positioned for decoding the attempt to speak could also allow the decoding of internal language. The precise neural differences between mental and produced language remain under investigation. In any case, the artificial intelligence was still able to decode some signals into phonemes, combining them to form words and sentences in real time, from a vocabulary of approximately 125 thousand words. The result? In two patients the system achieved an accuracy of 74%, and all this without any physical effort. In some tests, the BCI was also able to identify mentally counted numbers.
The privacy problem and the mental password: the limits of the system
Inner language, albeit with different intensity, shares some motor regions of the brain with attempted language. This raised the possibility that a BCI could end up decoding something the user only intended to thinkdon’t say it out loud. Although the interfaces were designed to decode the attempted language and, therefore, could generate distorted and inaccurate outputs when applied to the internal language, even the risk of being able to leak words that one wanted to “keep to themselves” raised an important ethical question.
The researchers’ ambition, therefore, was (and remains) to distinguish “motor intent” from silent intent to avoid the risk of unwanted output. They thus developed a model in which an internally spoken “keyword” can be detected with high precision, allowing the user to “lock” and “unlock” the system. It’s sort of switch mental which lights up only when a person imagines one “mental password” pre-established. In the case of the study, the selected phrase was “Chitty-Chitty-Bang-Bang“, recognized with an accuracy greater than 98%. In the absence of this key word, the system remains completely inactive. Privacy concerns are actually concrete: a device capable of translating thoughts could, in theory, also reveal contents not intended for communication; the mental switch instead imposes active consent before activation.
However, it is worth highlighting that Implanted BCIs are not yet an available technology and are still in the early stages of research and experimentation; they are also regulated by outside federal agencies to maintain the highest standards of medical ethics. Nonetheless, the idea that they could one day be widely disseminated is a truly promising prospect.
