It's Not Just Neuralink
The race to market to read your?thoughts
The goal of a clinical Motor BCI is to decode maximally valuable movement intentions (satisfying the User Outcomes ) from a remarkably small portion of the observable cortical tissue that encodes it.
Historically, most clinical Motor BCI studies used a high-channel count microelectrode “Utah Array ” to access the intracortical dynamics of motor control from humans and non-human primates (”iBCI”). For the past two decades, the Utah array remains the only intracortical device capable of discerning single neuron activity approved for use in humans (FDA 510(k) cleared) under the investigational device exception.
Since then, the Utah Array has been implanted in over 40 participants, with the largest (14 participants) longitudinal (nearly 50 total array-implant-years) study reporting a comparable safety profile to that of fully implanted neural interfaces such as DBS or the NeuroPace RNS system (Rubin et al., 2023 ):
“Large studies with over 100 patients undergoing DBS implantation have reported infection rates of between 3–5% of patients, of which up to half have required hardware removal. Other complications included subcortical hemorrhage, subdural hematoma, venous infarction, and seizure; these were observed in 1–5% of patients in case series. A meta-analysis of 1,714 patients who underwent DBS for essential tremor reported an infection rate of 3.4%, hemorrhage rate of 2.4%, and seizure rate of 2.3%. Device-specific complications, such as lead migration, misplaced leads, and implantable pulse generator failure have occurred at rates of about 3- 5%. In the long-term trial of the NeuroPace RNS, a chronically implanted neurostimulator used in the treatment of medication refractory epilepsy, the only device related SAE observed in >5% of the 230 enrolled participants was implantation site infection (in 12.1%), with no instances of meningitis or parenchymal brain infection (although bone flap osteomyelitis was observed). […] Our clinical research experience with a percutaneously connected, intracortical neural recording system has included only a single device-related skin infection, and no bone or CNS infections.”
While still considered the golden standard, Utah Array’s clinical limitations have manifested in no shortage of well-funded commercial ventures striving to improve its design or implantation. Importantly, many modern Motor BCI studies are based on Electrocorticography (”ECoG”) in which, instead of penetrating the cortical tissue, a grid of electrodes is placed on the surface of the brain subdurally or epidurally, covering many times larger cortical area at much lower electrode density. See Fig. 14 for a visual ranking of key high-resolution devices:
Emerging electrophysiological modalities include depth electrodes and endovascular electrodes, each believed to satisfy the spatiotemporal resolution and signal-to-noise ratio demands of a clinical Motor BCI system, although lacking the clinical track record of ECoG and iBCI. See Rapeaux and Constandinou Fig. 15, for a visual review:
?? This work does not intend to evaluate the viability of device-related attributes, nor itemize all possible recording modalities, but instead lay out the decoding achievements of available data acquisition modalities approaching clinical maturity.
Intracortical and depth electrodes may monitor extracellular spiking activity from surrounding neurons and may employ spike sorting strategies to attribute this activity to specific neurons (single-unit activity “SUA”). They, along with ECoG electrodes, may also aggregate the spiking activity of many neurons and use those features for analysis (multiunit activity “MUA”) (Konerding et al., 2018 , Hermiz et al., 2020 ). Lastly, they all may gather in local field potential (”LFP”), which reflects the aggregate activity of local populations of neurons too distant (or separated by a vascular wall in the case of endovascular electrodes (Thielen et al., 2023 )) to yield discernible waveforms.
The Utah Array paved the way for other technologies transducing ion currents into electronic ones to gain a nod from the regulators to start clinical trials. Namely:
Although originally intending to conduct a clinical trial to restore speech using their novel graphene-based Motor BCI (BrainCom, 2022 ), INBRAIN Neuroelectronics has since pivoted to focus on deep brain stimulation therapy for Parkinson’s disease?—?receiving FDA Breakthrough designation in this category (INBRAIN, 2023 ). Carrying the EU torch, CorTec?—?part of another large European consortium “INTERCOM ”?—?is preparing to use their Brain Interchange One implant to restore communication to those in LIS (Wyss Center, 2022 ).
This handful of high-performance Motor BCI startups share over $2 billion in funding without a single product approved for use in the clinical market by regulators such as the Food and Drug Administration (”FDA”).
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Analogous Interventions
It is natural to be skeptical of an early-phase technology, especially one that is expected to venture into and coexist with a body part most central to who we are. However, invasive procedures depositing an implant are not uncommon, some are even pursued for aesthetic reasons.
In 1982, the FDA placed breast implants in the rigorous Class III category (the same as the most invasive Motor BCIs) for reports of adverse events in the medical literature. 24 years later, the FDA lifted restrictions on silicone breast implants and, in 2010, they became the most popular form of plastic surgery in the US (Reuters Staff, 2012 ).
Now, over 500,000 people volunteer each year to undergo invasive breast surgeries for self-affirming aesthetic reasons in the US alone. What is more, these interventions are elective and therefore not covered by insurance. The mean out-of-pocket cost of breast implants is $4,294 (Aesthetic Society, 2022 ; American Society of Plastic Surgeons, 2022 ).
Tens of millions of women live with breast implants, a reality unimaginable to most folks of the 20th century. Closer to the brain, nearly a million people live with a cochlear implant, restoring one’s hearing by feeding an electrical current to the periphery of the central nervous system (NIH, 2019 ). In a similar manner, even inside the brain, several hundred thousand people live with an aforementioned DBS, primarily reducing the symptoms of Parkinson’s disease and essential tremor (Lozano and Lipsman, 2013 ).
????♂? The anticipated high-channel-count Motor BCI differs from prior implanted devices in that the implant itself generates little value to the User. Rather, it is an essential bridge between the User’s mind and external devices. The value is instead realized by the capabilities of these external devices; effectively utilizing the unique window into User’s motor intentions.
However unimaginable, Motor BCIs are poised to follow a similar, if not accelerated (FDA, 2023 ), trajectory to market to other implanted interventions. Should Motor BCIs prove valuable and safe across the severely paralyzed population, their ability to scale to the hundreds of millions of people living with motor impairments largely depends on the appeal of the clinical outcomes they may achieve.
Part 4 of a series of unedited excerpts from uCat: Transcend the Limits of Body, Time, and Space by ?? Sam Hosovsky *, Oliver Shetler , Luke Turner , and Cai K . First published on Feb 29th, 2024, and licensed under CC BY-NC-SA 4.0.
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Sam was the primary author of this excerpt.
Field Clinical Engineer | Neurotech ??
6 个月Thanks for this nice overview of the neurotech/BCI panorama
Matrix-level VR @ uCat
7 个月Update: Re-uploaded a corrupted picture