Neuralink Implant Updates: Managing Hardware Challenges in Human Trials

The journey of the first human patient to receive a Neuralink brain-chip has provided incredible data, but it has not been without complications. Following the highly publicized surgery in January 2024, Neuralink revealed that their first trial participant encountered a specific hardware malfunction involving the device’s microscopic wiring. This development offers a rare look into the real-time problem-solving required in the high-stakes field of brain-computer interfaces (BCIs).

The Issue: Retracting Threads in the N1 Implant

In May 2024, Neuralink disclosed that Noland Arbaugh, the first human recipient of the N1 implant, experienced a reduction in the device’s performance weeks after his surgery. The root cause was identified as “thread retraction.”

The N1 implant relies on 64 flexible threads, each thinner than a human hair, which contain a total of 1,024 electrodes. These electrodes are responsible for detecting neural activity in the motor cortex and translating it into digital signals. According to the company, a number of these threads pulled back or retracted from the brain tissue.

When these threads retracted, the number of effective electrodes decreased. This resulted in a drop in bits-per-second (BPS), which is the standard metric used to measure the speed and accuracy of cursor control. Essentially, the “signal” from Arbaugh’s brain became weaker, making the computer cursor lag or respond less accurately to his thoughts.

Why Did the Threads Retract?

The brain is not a static object. It is a soft, gelatinous organ that floats in cerebrospinal fluid inside the skull. It moves slightly when we breathe or when our heart beats. Additionally, the introduction of air into the skull during surgery (a condition known as pneumocephalus) can create space that allows for more movement in the days following the procedure.

While Neuralink has not pinpointed a single definitive cause, the movement of the brain relative to the skull-anchored casing of the N1 device likely contributed to the threads slipping out of their targeted position.

The Software Solution: Fixing Hardware with Code

When the issue was discovered, the immediate concern for outside observers was whether Arbaugh would require a second brain surgery to replace or adjust the threads. However, Neuralink engineers opted for a software-based solution that proved highly effective.

Rather than physically intervening, the team overhauled the recording algorithm. Originally, the system was tuned to listen for specific neuron firing patterns. The engineers modified the recording system to be more sensitive to neural population signals. This means the software began listening to the average power of a group of neurons rather than relying solely on individual spikes.

The results of the software update included:

• Signal Sensitivity: The device could pick up weaker signals from the threads that remained in place.
• Cursor Recovery: Arbaugh’s cursor control speed and accuracy recovered rapidly.
• Enhanced Performance: Following the update, Arbaugh was essentially able to beat his previous performance records, despite having fewer functional electrodes connecting to his brain.

Impact on the Patient: Noland Arbaugh’s Experience

Noland Arbaugh, a 29-year-old who became quadriplegic after a diving accident, has remained optimistic throughout the process. Despite the retraction issue, the utility of the device remains significantly higher than previous assistive technologies he has used.

Since the software update, Arbaugh uses the implant for extended sessions, often exceeding eight hours a day. He utilizes the Link to browse the internet, manage messages, and play complex video games. He has been specifically noted for playing Civilization VI and Mario Kart, activities that require precise and sustained cursor control. The hardware issue has not posed a direct safety risk to his health, and he has not reported pain or cognitive side effects related to the thread retraction.

Adjustments for Future Trials

The data gathered from Arbaugh’s experience is directly influencing how Neuralink approaches its next patients. The FDA has reportedly given the green light for a second participant in the PRIME Study (Precise Robotically Implanted Brain-Computer Interface).

To prevent thread retraction in the second patient and subsequent trials, Neuralink is adjusting its surgical approach. Reports indicate the company plans to implant the threads deeper into the brain tissue.

• Previous Depth: Approximately 3mm to 5mm into the motor cortex.
• New Target Depth: Approximately 8mm.

By placing the threads deeper, the company hopes to anchor them more securely within the cortex, reducing the likelihood that the brain’s natural movements will cause them to slip out.

Context: Neuralink vs. Traditional BCIs

It is helpful to understand where this issue fits in the broader timeline of brain interface technology. Traditional implants, such as the Utah Array used by competitors like Blackrock Neurotech, utilize rigid spikes that penetrate the brain. While these are stable, the rigid nature can cause scar tissue buildup over time, which degrades the signal.

Neuralink’s flexible threads were designed specifically to minimize this scarring and “move” with the brain. The retraction issue highlights the engineering trade-off: flexible threads are safer for tissue long-term but are mechanically harder to keep in place compared to rigid spikes.

Other competitors, such as Synchron, avoid this specific problem entirely by not entering the skull. Synchron’s “Stentrode” travels through blood vessels to sit near the motor cortex without penetrating brain tissue. However, this method generally offers lower bandwidth (slower data speeds) compared to Neuralink’s direct connection.

Frequently Asked Questions

Did the threads retracting hurt the patient? No. The brain itself lacks pain receptors. Noland Arbaugh did not feel the threads moving or retracting. The primary symptom was a lag in the responsiveness of the computer cursor he was controlling.

Will Neuralink remove the implant because of this? There are no current plans to remove the implant from the first patient. Because the software update successfully restored functionality, Arbaugh continues to use the device daily for personal and research tasks.

Is the Neuralink implant available to the public? No. The N1 implant is currently in the clinical trial phase (the PRIME Study). It is only available to a very small number of selected participants who meet strict medical criteria, primarily those with quadriplegia due to cervical spinal cord injury or ALS. Widespread commercial availability is likely many years away.

What is the ‘PRIME’ study? PRIME stands for Precise Robotically Implanted Brain-Computer Interface. It is the investigational medical device trial designed to evaluate the safety of the N1 implant and the R1 surgical robot. The goal is to prove the system is safe and effective for restoring communication and mobility in people with paralysis.