Mind-reading devices can now predict preconscious thoughts: is it time to worry?

Summary

Before a car crash in 2008 left her paralysed from the neck down, Nancy Smith enjoyed playing the piano. Years later, Smith started making music again, thanks to an implant that recorded and analysed her brain activity. When she imagined playing an on-screen keyboard, her brain–computer interface (BCI) translated her thoughts into keystrokes — and simple melodies, such as ‘Twinkle, Twinkle, Little Star’, rang out1.The rise of brain-reading technology: what you need to knowBut there was a twist. For Smith, it seemed as if the piano played itself. “It felt like the keys just automatically hit themselves without me thinking about it,” she said at the time. “It just seemed like it knew the tune, and it just did it on its own.”Smith’s BCI system, implanted as part of a clinical trial, trained on her brain signals as she imagined playing the keyboard. That learning enabled the system to detect her intention to play hundreds of milliseconds before she consciously attempted to do so, says trial leader Richard Andersen, a neuroscientist at the California Institute of Technology in Pasadena.Smith is one of roughly 90 people who, over the past two decades, have had BCIs implanted to control assistive technologies, such as computers, robotic arms or synthetic voice generators. These volunteers — paralysed by spinal-cord injuries, strokes or neuromuscular disorders, such as motor neuron disease (amyotrophic lateral sclerosis) — have demonstrated how command signals for the body’s muscles, recorded from the brain’s motor cortex as people imagine moving, can be decoded into commands for connected devices.But Smith, who died of cancer in 2023, was among the first volunteers to have an extra interface implanted in her posterior parietal cortex, a brain region associated with reasoning, attention and planning. Andersen and his team think that by also capturing users’ intentions and pre-motor planning, such ‘dual-implant’ BCIs will improve the performance of prosthetic devices.Nancy S...