Intracortical Electrodes

Rats implanted with microwire arrays showed an exponential-like fall in intracortical microstimulation (ICMS) perception thresholds from weeks 5 to 12, then held near a fitted asymptote of about 1.1 nC/ph per electrode across 10 stimulating electrodes through week 30 in animals that retained detectable percepts. Correct responses to the conditioned stimulus stabilized at roughly 90%. Neither the arrays' electrophysiological nor their electrochemical properties explained the threshold trend across animals. Gene expression in implanted tissue showed elevated Gfap and Cd68 alongside reduced NeuN and Bdnf, consistent with earlier neuroinflammation findings. Two animals lost sensation over the 30-week period.

A single-author study presents a hybrid algorithm for telling apart spikes from the many neurons an implanted electrode records at once, a step a brain-computer interface (BCI) must take before it can decode intent. A deep neural network assigns each spike to a neuron and estimates its waveform, fuzzy-logic methods detect spikes and score confidence when signal quality is uncertain, and the network architecture was chosen by multi-objective selection. On four datasets from rat cortex, hippocampal CA1 and monkey motor cortex, it reached 96.4% accuracy, 94.8% precision and a mean latency of 45.2 ms with full labels, and 88.9% accuracy with only 10% of data labeled, which the author says is comparable to existing unsupervised methods while also providing confidence and waveform estimates. The author notes that prospective validation is needed before clinical use.

After days of practicing a brain-computer interface with adaptive decoders, rhesus macaques needed significantly fewer motor cortex neurons to reach 80% task classification accuracy than in early sessions (p = 9.8 x 10^-4). Fixed decoders produced no such compaction. A neural network model suggests the adaptive decoders directly contribute to these more compact representations; the authors propose this may be because the decoders alter the error information used for credit assignment. The finding implies that assistive algorithms do not merely boost immediate BCI performance but actively reshape how the brain learns over time -- a consideration for real-world decoder design. The study used 128-channel microwire arrays in motor and premotor cortices of two monkeys and has not been tested in humans.

During removal of a right parafalcine meningioma, surgeons placed four Layer 7 μECoG arrays, 4,096 electrodes in total, on either side of the central sulcus and recorded somatosensory evoked potentials under 5 contralateral stimulation conditions. Using a 2 MΩ impedance cutoff, 3,739 channels were usable, a 91.3% yield; phase-reversal latencies were 19, 21, 25, 26 and 25 ms, consistent with the standard intraoperative mapping performed in the same operation. The researchers caution that the setup provides dense spatial sampling rather than submillimeter physiological resolution: measured responses were correlated across roughly 3–4 mm of cortex.

Training a decoder to read brain signals usually means collecting a large labeled dataset from every new subject, which is slow and a burden on patients. The proposed method, MAPA, first runs self-supervised pretraining on unlabeled intracranial EEG recordings pooled across subjects, then transfers to new ones. The difficulty is that electrode contact placement and neuroanatomy vary from person to person, so MAPA adds two spatial encodings, an anatomical region embedding and a relative positional encoding, to a standard masked autoencoder. In cross-subject tests, about 164 labeled trials were enough to reach the accuracy that otherwise takes 3,500. The team reports that MAPA set new best results on the Neuroprobe benchmark in all three settings, within-session, cross-session and cross-subject, without fine-tuning, suggesting that calibration for implanted BCIs could become much shorter.

A research team built an EEG motor-imagery brain-computer interface and connected its decoder to a physical differential-drive wheelchair prototype, offering people with severe motor impairments a non-invasive means of control, though the uncertainty of EEG decoding has long hindered such systems from driving physical actuators. Using Filter Bank Common Spatial Pattern features on a public dataset, the team compared support vector machine (SVM), k-nearest neighbors and linear discriminant analysis classifiers; SVM reached 90.7% mean accuracy, and 85.9% when replayed on an independent dataset through a hardware-in-the-loop setup. Confidence-based command validation raised accuracy among accepted commands to 97.6%, at the cost of accepting only 60.7% of them. Layered safeguards (confidence gating, self-terminating steering, transition braking, communication timeout supervision and a hardware emergency cutoff) limit the consequences of decoding errors.

A team from the University of Utah, Kangwon National University and the University of Georgia describes a silicon-free route to neural microelectrode arrays: soft polymeric 3D microneedles are printed by two-photon polymerization, then turned into electrodes by injecting liquid gallium into the hollow channels. A newly defined retention number predicts whether the gallium stays put under physiological conditions. Coating the surface with gold nanoparticles and PEDOT doped with tetrafluoroborate cut impedance by roughly 3 orders of magnitude, and in vivo recordings in an invertebrate model captured neural spikes with no gallium leakage. The study was published in ACS Sensors on August 31, 2026.

Intracortical recordings from 3 BrainGate2 participants show preparatory motor cortex activity encodes movement direction, curvature, and distance, enabling preparatory-activity-based online cursor control.

Researchers address the challenge of unifying consent standards for implantable brain-computer interfaces.

US researchers using intracortical microelectrode arrays identified distinct neural patterns in the motor and somatosensory cortex of patients with spinal cord injury that separately encode the timing and force of grasping, offering new ideas for developing more precise brain-computer interface (BCI) systems.

The study uses spatial proteomics to assess tissue around non-functional intracortical microelectrodes implanted for four weeks in mice, measuring neuronal integrity, immune-cell activation and local cytokine expression around probes coated with drug-loaded, controlled-release titanium dioxide nanotube array (TNA) coatings. The authors note that blood-brain barrier disruption can translocate gut-derived bacteria to the implant site and sustain chronic inflammation, and that the TNA coating's therapeutic loading and controlled release further damp residual neuroinflammation. They conclude that TNA offers a multifunctional, tunable interface for locally regulating the neuroimmune microenvironment, a step toward long-term reliable intracortical recordings.

Researchers evaluated ruthenium-oxide-coated amorphous silicon-carbide microelectrode arrays during 25 weeks of intracortical microstimulation in rodents. Perception thresholds stabilized at about 0.4 nC per phase per electrode by week nine, behavioral performance remained around 91%, and reliable sensation persisted through week 25.

Researchers decoded 15 semantic categories from sEEG high-gamma activity in epilepsy patients at 29.8% accuracy (chance 6.7%), supporting semantic decoding feasibility for language BCIs. Preprint; not yet peer-reviewed.

Sun Yat-sen University researchers propose a minimally invasive hybrid BCI using 300-800 um skull micro-holes for distributed microelectrodes; rat experiments show improved SNR over scalp EEG. Preprint; not yet peer-reviewed.

A study examining the potential brain risk of BCI electrodes exposed to strong electromagnetic fields applied nuclear electromagnetic pulse (NEMP) irradiation to rats with implanted brain electrodes and recorded local field potentials (LFPs) in the primary motor cortex (M1). At 200 kV/m, NEMP inhibited the alpha and delta LFP bands in resting rats, an effect linked to front-gate coupling between the pulse and the electrode, with the coupled current stimulating the brain and affecting its state of consciousness; the authors frame the work as early animal data for BCI electromagnetic protection.

Using implantable brain-machine interface (iBMI) data from a non-human primate two-dimensional finger task, the study tests whether brain-muscle synergies improve decoding performance and generalization. Principal component analysis (PCA), demixed PCA (dPCA) and non-negative matrix factorization (NMF) all compressed brain-muscle data effectively with minimal decoding-accuracy loss, but none improved performance through denoising or enhanced cross-task generalization. The authors conclude that extracting synergies alone does not yield a better or cleaner control space for linear decoding, and call for larger samples and more muscle channels.

Two people with tetraplegia typed on a virtual two-handed QWERTY keyboard simply by attempting finger movements, which electrodes implanted in the brain decoded into keystrokes. Typing speed was set by the users and reached 110 characters per minute, or 22 words per minute, with a word error rate of 1.6%, which the authors say resembles able-bodied typing accuracy. Accurate decoding required as few as 30 calibration sentences, and a 5-gram language model improved sentence output. One participant has amyotrophic lateral sclerosis (ALS) and the other a spinal cord injury.

Neuralink said its clinical trials worldwide now include 21 participants. After making surgical and postoperative changes in response to thread retraction in the first recipient, the company reported higher signal quality in 18 of the next 20 participants. The figures come from a company update rather than a peer-reviewed clinical report.

Researchers discuss how recent BCI advances in electrode longevity and biocompatibility could address key olfactory implant challenges.

A Neuron paper describes Neuropixels Ultra, which packs 6,144 switchable recording sites at 6-micrometer center-to-center spacing while reading 384 channels simultaneously. In mouse visual cortex recordings, neuronal yield increased by more than twofold. The study also improved subcellular signal detection and cell-type classification, but it did not report simultaneous recording from 10,000 neurons.

Neuralink said thread retraction in its first PRIME participant temporarily reduced BCI performance before the threads stabilized and performance recovered. For the second implant, the team reduced brain motion during surgery and narrowed the gap between the implant and the brain surface. The company reported no thread retraction in the second participant at the time, but it did not publish channel-attrition rates or a formal interim safety report.

The FDA granted Breakthrough Device designation to Blackrock Neurotech's MoveAgain BCI System on November 16, 2021. The investigational system combines an implanted array, neural decoding and wireless output with the goal of allowing people with severe paralysis to control digital and assistive devices. The designation can expedite development and review but is not market approval.