How AI is learning to convert brain signals into speech
The first steps toward developing tools that could help disabled people regain the power to speak.
- The technique involves training neural networks to associate patterns of brain activity with human speech.
- Several research teams have managed to get neural networks to "speak" intelligible words.
- Although similar technology might someday help disabled people regain the power to speak, decoding imagined speech is still far off.
Several research groups have recently made significant progress in using neural networks to convert brain activity into intelligible computer-generated speech, developments that could mark some of the first steps toward radically improving the quality of life for people who've lost the ability to speak.
As a recent article from Science notes, the groups, which have published several separate papers on the preprint server bioRxiv, aren't yet able to convert people's purely imagined words and sentences into computer-generated speech. Still, the teams were successful in getting neural networks to reconstruct words that various participants had either heard, spoken aloud or mouthed silently.
To accomplish that, the teams recorded brain signals and fed them to a neural network, which then matched the signals with associated sounds or mouth movements.
Unfortunately, this kind of work requires opening the skull; researchers need extremely precise data that can only be obtained by surgically implanting electrodes directly onto regions of the brain associated with speech, listening or motor functioning. Making matters more complicated is the fact that each person shows unique neural activity in these regions, so what an AI learns from one person doesn't translate to the next.
"We are trying to work out the pattern of … neurons that turn on and off at different time points, and infer the speech sound," Nima Mesgarani, a computer scientist at Columbia University, told Science. "The mapping from one to the other is not very straightforward."
For the research, the teams relied on participants who were already scheduled to undergo invasive surgery to remove brain tumors or receive pre-surgery treatments for epilepsy.
One team, led by Mesgarani, fed a neural network with data from participants' auditory cortexes that was obtained while they listened to recordings of people telling stories and listing numbers. Using the brain data alone, the neural network was able to "speak" numbers to a group of listeners who were able to identify the digits correctly about 75 percent of the time.
Another team, led by neurosurgeon Edward Chang and his team at the University of California, San Francisco, recorded epilepsy patients' brain activity as they read sentences aloud, and fed the data to a neural network. A separate group of people then listened to the neural network's attempts to reconstruct the sentences, and after selected from a written list which sentences they thought it was trying to reproduce. In some cases, they chose correctly 80 percent of the time.
Chang's team also managed to get a neural network to reproduce words that participants had only mouthed silently, an achievement that marks "one step closer to the speech prosthesis that we all have in mind," as neuroscientist Christian Herff at Maastricht University in the Netherlands told Science.
Deciphering imagined speech
A scene from The Diving Bell and the Butterfly (2007).
The techniques described above work because neural networks were able to find patterns between two relatively defined sets of data: brain activity and external speech functions (such as spoken words or mouth movements). But those external functions aren't present when someone merely imagines speech, and, without that data to use for training, it's unclear whether neural networks would ever be able to translate brain activity into computer-generated speech.
One approach, as Herff told Science's Kelly Servick, involves giving "feedback to the user of the brain-computer interface: If they can hear the computer's speech interpretation in real time, they may be able to adjust their thoughts to get the result they want. With enough training of both users and neural networks, brain and computer might meet in the middle."
It's still speculative, but it's easy to see how technology of the sort could greatly improve the lives of people who've lost the ability to speak, many of whom rely on speech-assist technology that requires people to make tiny movements in order to control a cursor that selects symbols or words. The most famous example of this is the system used by Stephen Hawking, who described it like this:
"My main interface to the computer is through an open source program called ACAT, written by Intel. This provides a software keyboard on the screen. A cursor automatically scans across this keyboard by row or by column. I can select a character by moving my cheek to stop the cursor. My cheek movement is detected by an infrared switch that is mounted on my spectacles. This switch is my only interface with the computer. ACAT includes a word prediction algorithm provided by SwiftKey, trained on my books and lectures, so I usually only have to type the first couple of characters before I can select the whole word. When I have built up a sentence, I can send it to my speech synthesizer. I use a separate hardware synthesizer, made by Speech Plus. It is the best I have heard, although it gives me an accent that has been described variously as Scandinavian, American or Scottish."
Malcolm Gladwell teaches "Get over yourself and get to work" for Big Think Edge.
- Learn to recognize failure and know the big difference between panicking and choking.
- At Big Think Edge, Malcolm Gladwell teaches how to check your inner critic and get clear on what failure is.
- Subscribe to Big Think Edge before we launch on March 30 to get 20% off monthly and annual memberships.
The 21st century is experiencing an Asianization of politics, business, and culture.
- Our theories about the world, even about history or the geopolitics of the present, tend to be shaped by Anglo perspectives of the Western industrial democracies, particularly those in the United States and the United Kingdom.
- The West, however, is not united. Canada, for instance, acts in many ways that are not in line with American or British policies, particularly in regard to populism. Even if it were united, though, it would not represent most of the world's population.
- European ideas, such as parliamentary democracy and civil service, spread across the world in the 19th century. In the 20th century, American values such as entrepreneurialism went global. In the 21st century, however, what we're seeing now is an Asianization — an Asian confidence that they can determine their own political systems, their own models, and adapt to their own circumstances.
Research has shown that men today have less testosterone than they used to. What's happening?
- Several studies have confirmed that testosterone counts in men are lower than what they used to be just a few decades ago.
- While most men still have perfectly healthy testosterone levels, its reduction puts men at risk for many negative health outcomes.
- The cause of this drop in testosterone isn't entirely clear, but evidence suggests that it is a multifaceted result of modern, industrialized life.
Can sensitive coral reefs survive another human generation?
- Coral reefs may not be able to survive another human decade because of the environmental stress we have placed on them, says author David Wallace-Wells. He posits that without meaningful changes to policies, the trend of them dying out, even in light of recent advances, will continue.
- The World Wildlife Fund says that 60 percent of all vertebrate mammals have died since just 1970. On top of this, recent studies suggest that insect populations may have fallen by as much as 75 percent over the last few decades.
- If it were not for our oceans, the planet would probably be already several degrees warmer than it is today due to the emissions we've expelled into the atmosphere.
SMARTER FASTER trademarks owned by The Big Think, Inc. All rights reserved.