PRIME Study Progress Update — User Experience

It is estimated that 180,000 Americans live with quadriplegia, and each year, an additional ~18,000 suffer a paralyzing spinal cord injury. We live in a digital society where‬‭ much of our work, entertainment, and social lives rely heavily on our use of computers and‬‭ smart devices. People with quadriplegia often find that their needs to engage seamlessly with the digital world go unmet, leading to decreased independence, isolation, and financial challenges. Our goal is to provide a high-performance interface that will enhance the control of digital devices for people with quadriplegia, unlocking their personal and professional potential.

The first step toward this goal was achieved just over 100 days ago at Barrow Neurological Institute in Phoenix Arizona, where Noland Arbaugh, the first participant of the PRIME Study*, received his Neuralink implant (Link). As noted in our last blog post, the surgery went extremely well, and he was able to go home the following day.

The aim of the PRIME Study is to demonstrate that the Link is safe and useful in daily life. We will monitor its technical performance remotely and quantify any benefit it provides by timing the duration of independent use and assessing how it affects study participants’ quality of life.

Prior to having the Link, Noland’s primary digital interface was a mouth-held tablet stylus (mouth stick) that had to be put in place by a caregiver. The mouth stick can only be used in the upright position to operate a tablet. With prolonged use it can lead to discomfort, muscle fatigue, and pressure sores; it also prevents normal speech.

In the weeks since his surgery, Noland has used the Link to control his laptop from various positions, including while lying down in bed. He plays online computer games with friends (Chess, Civilization VI), browses the internet, live streams, and uses other applications on his MacBook, all by controlling a cursor with his mind. He has even used the Link to play Mario Kart on a Nintendo Switch console — something he had not been able to do since his spinal cord injury.

On weekdays, Noland contributes to research sessions for up to 8 hours per day. On weekends, personal use and recreation can exceed 10 hours per day (Fig 02). Recently, he used the device for a total of 69 hours in a single week: 35 hours of structured sessions and an additional 34 hours of personal use.

Participation in research sessions allows us to evaluate the performance of the Link. The standard measure for speed and accuracy of cursor control is bits-per-second (BPS), calculated using a grid task (Fig 03). Higher BPS values indicate better cursor control. During his first-ever research session, Noland set a new world record for human BCI cursor control of 4.6 BPS. He has subsequently achieved 8.0 BPS and is currently trying to beat scores of the Neuralink engineers using a mouse (~10 BPS). The Link is able to distinguish left and right clicks and allows cursor control sufficiently precise to select targets similar in size to the smallest icons and buttons on a laptop screen (Fig 03). The ability to select small targets using multiple click types allows Noland to use applications and play games on his laptop that were not possible with his mouth stick.

In the weeks following the surgery, a number of threads retracted from the brain, resulting in a net decrease in the number of effective electrodes. This led to a reduction in BPS (Fig 04). In response to this change, we modified the recording algorithm to be more sensitive to neural population signals, improved the techniques to translate these signals into cursor movements, and enhanced the user interface. These refinements produced a rapid and sustained improvement in BPS, that has now superseded Noland’s initial performance.

Our current work is focused on pushing cursor control performance to the same level as that of able-bodied individuals, and on expanding functionality to include text entry. In the future we intend to extend the Link’s functionality to the physical world to enable control of robotic arms, wheelchairs, and other technologies that may help increase independence for people living with quadriplegia.

If you are excited to restore autonomy to those with unmet medical needs, consider applying to our open roles. If you are interested in shaping the future of assistive technologies by participating in a Neuralink clinical trial, please join our Patient Registry.

* The PRIME Study — an investigational medical device trial for our fully implantable, wireless brain-computer interface (BCI) — aims to evaluate the safety of our implant and surgical robot, and assess the initial functionality of our BCI for enabling people with quadriplegia to control external devices with their thoughts. We do not guarantee any benefit by participating in the PRIME Study.