An Integrated Brain-Machine Interface Platform With Thousands of Channels

Abstract

Brain-machine interfaces hold promise for the restoration of sensory and motor function and the treatment of neurological disorders, but clinical brain-machine interfaces have not yet been widely adopted, in part, because modest channel counts have limited their potential. In this white paper, we describe Neuralink's first steps toward a scalable high-bandwidth brain-machine interface system. We have built arrays of small and flexible electrode "threads," with as many as 3072 electrodes per array distributed across 96 threads. We have also built a neurosurgical robot capable of inserting six threads (192 electrodes) per minute. Each thread can be individually inserted into the brain with micron precision for avoidance of surface vasculature and targeting specific brain regions. The electrode array is packaged into a small implantable device that contains custom chips for low-power on-board amplification and digitization: The package for 3072 channels occupies less than 23×18.5×2 mm³. A single USB-C cable provides full-bandwidth data streaming from the device, recording from all channels simultaneously. This system has achieved a spiking yield of up to 70% in chronically implanted electrodes. Neuralink's approach to brain-machine interface has unprecedented packaging density and scalability in a clinically relevant package.

Keywords: brain-machine interface; motor function; neurology; sensory function.

Figure 1

Our novel polymer probes. (A) “Linear Edge” probes, with 32 electrode contacts spaced by 50 μm. (B) “Tree” probes with 32 electrode contacts spaced by 75 μm. (C) Increased magnification of individual electrodes for the thread design in panel A, emphasizing their small geometric surface area. (D) Distribution of electrode impedances (measured at 1 kHz) for two surface treatments: PEDOT (n=257) and IrOx (n=588). IrOx: iridium oxide; PEDOT: poly-ethylenedioxythiophene; PCB: printed circuit board.

Figure 2

Needle pincher cartridge compared with a penny for scale. (A) Needle. (B) Pincher. (C) Cartridge.

Figure 3

Insertion process into an agarose brain proxy. (1) The inserter approaches the brain proxy with a thread. (i) needle and cannula. (ii) Previously inserted thread. (2) Inserter touches down on the brain proxy surface. (3) Needle penetrates tissue proxy, advancing the thread to the desired depth. (iii) Inserting thread. (4) Inserter pulls away, leaving the thread behind in the tissue proxy. (iv) Inserted thread.

Figure 4

The robotic electrode inserter; enlarged view of the inserter-head shown in the inset. (A) Loaded needle pincher cartridge. (B) Low-force contact brain position sensor. (C) Light modules with multiple independent wavelengths. (D) Needle motor. (E) One of four cameras focused on the needle during insertion. (F) Camera with wide angle view of the surgical field. (G) Stereoscopic cameras.

Figure 5

A packaged sensor device. (A) Individual neural processing application-specific integrated circuit capable of processing 256 channels of data. This particular packaged device contains 12 of these chips for a total of 3072 channels. (B) Polymer threads on parylene-c substrate. (C) Titanium enclosure (lid removed). (D) Digital USB-C connector for power and data.

Figure 6

Thread implantation and packaging. (A) An example perioperative image showing the cortical surface with implanted threads and minimal bleeding. (B) Packaged sensor device (“System B”) chronically implanted in a rat.

Figure 7

The broadband signals recorded from a representative thread. Left: Broadband neural signals (unfiltered) simultaneously acquired from a single thread (32 channels) implanted in rat cerebral cortex. Each channel (row) corresponds to an electrode site on the thread (schematic at left; sites spaced by 50 μm). Spikes and local field potentials are readily apparent. Right: Putative waveforms (unsorted); numbers indicate channel location on thread. Mean waveform is shown in black.

Figure 8

Our devices allow the recording of widespread neural activity distributed across multiple brain regions and cortical layers. Left: Thread insertion sites (colored circles) are indicated on the rendered rodent brain [38]. Right: Raster of 1020 simultaneously recorded channels, sorted per thread (color corresponds to insertion site). Inset: Enlarged raster of spikes from a single thread. This thread corresponds to the one shown in Figure 7.