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The BCI Briefing

TechnologyHow do neural interfaces work?

How we interface with the nervous system

Every neural interface trades access, resolution and invasiveness against each other. This explorer places 32 of them on one map, by what they do and how far they have come, so that an EEG cap, a deep brain stimulator and an intracortical array can be read on the same terms.

BCI is evolving from decoding the nervous system to interacting with it.

  1. Reading
  2. Writing
  3. Closed loop
  4. Biohybrid

32 interfaces

Read

Bidirectional

Write

Non-invasive

Around the head

On the skin

Minimally invasive

Vessel or skull window

Invasive

Nerve or sense organ

On the cortex

In the cortex

Deep brain

Biohybrid · Adjacent frontier

Living neural tissue outside the body. Not an interface with a person.

Fig. 01 — The interface design spacePosition shows function and access. Fill shows maturity. Select an interface.

Colour · function

  • Read
  • Write
  • Bidirectional
  • Biohybrid

Fill · maturity as a clinical modality

  • Established
  • Human feasibility
  • Early human
  • Preclinical
  • Research frontier
  • Adjacent frontier

ReadInvasiveElectrical

Intracortical arrays

Microelectrodes penetrate a millimetre or so into cortex and record the spiking of individual neurons and small groups of neurons.

Showing Intracortical arrays: Read, Invasive.

Where it acts
Inside the cortex
Information flow
Cortex → penetrating array
Loading cortical surface…
Fig. 02 — Where it acts, and which way information flowsSchematic placement on a group-average cortical surface. Drag to rotate. Not a specific device or a surgical plan.

How far it has come

As a clinical modality
Human feasibilityResearch implants in people since 2004. Not a routine clinical tool.
As a BCI application
Human feasibilityFeasibility studies across several groups and companies; the basis of the leading speech results.
Access
Invasive
Mechanism
Electrical
Target
Cortex
Signal
Action potentials and local field potentials

Characteristics · read interfaces

Spatial resolutionSingle neurons
Temporal resolutionSub-millisecond
Signal richnessSpikes from individual neurons
CoverageA few mm² per array
InvasivenessCraniotomy; penetrating insertion
Long-term stabilityChanges over months to years; varies by design

Each track runs from low to high. A wide bar means the characteristic varies across implementations.

Strengths

  • Highest information rate demonstrated in people
  • Basis of the leading speech and handwriting results

Trade-offs

  • Samples a small patch of cortex
  • Long-term signal stability and tissue response remain open questions

Common applications

  • Speech and communication
  • Cursor and device control
  • Robotic arm control

Human evidence

Two decades of peer-reviewed results, mostly from single participants: handwriting at 90 characters per minute (2021), speech at 62 words per minute (2023), and 97.5% word accuracy held over 8.4 months (2024).

What needs to happen next

Longevity data for the newer electrode designs, and a pivotal trial.

Same site, other direction
Used by
NeuralinkParadromicsBlackrock NeurotechBrainGateStairMedNeuCyber NeuroTechAxoft
Research
An Accurate and Rapidly Calibrating Speech NeuroprosthesisAn instantaneous voice-synthesis neuroprosthesisA high-performance speech neuroprosthesisInner speech in motor cortex and implications for speech neuroprostheses+11 more
Clinical
PRIMEVOICECAN-PRIMEGB-PRIMEUAE-PRIMEConnect-One+6 more
Tools
Open Ephys GUIezmsgSpikeInterfaceKilosorttorch_brainBRAND+2 more
Datasets
Brain-to-Text '25Brain-to-Text Benchmark '24Handwriting BCI datasetFALCON benchmark
Use cases
CommunicateControlMoveFeelSee
On the calendar
BCI Meeting 2027
Patent activity
90 patent families name this interface, most often on electrodes and arrays, stimulation, neural decoding. The patent landscape

Descriptions, ranges and maturity levels are editorial analysis, kept qualitative where the literature does not support exact comparison across technologies. Specific devices differ.

All 32 interfaces as a table
Every interface, with its function, access, mechanism, target and maturity
InterfaceFunctionAccessMechanismTargetClinical modalityBCI application
ReadNon-invasiveElectricalCortexEstablishedHuman feasibility
ReadNon-invasiveMagneticCortexEstablishedResearch frontier
ReadNon-invasiveOpticalCortexHuman feasibilityResearch frontier
ReadNon-invasiveElectricalMuscle / neuromotorEstablishedEstablished
ReadMinimally invasiveElectricalCortexHuman feasibilityHuman feasibility
ReadMinimally invasiveAcousticCortex, Deep brainEarly humanPreclinical
ReadInvasiveElectricalPeripheral nerve, Muscle / neuromotorEarly humanEarly human
ReadInvasiveElectricalCortexEstablishedHuman feasibility
ReadInvasiveElectricalCortexHuman feasibilityHuman feasibility
ReadInvasiveElectricalDeep brain, CortexEstablishedEarly human
WriteNon-invasiveMagneticCortexEstablishedResearch frontier
WriteNon-invasiveElectricalCortexHuman feasibilityResearch frontier
WriteNon-invasiveAcousticCortex, Deep brainEarly humanResearch frontier
WriteInvasiveElectricalPeripheral nerveEstablishedEarly human
WriteInvasiveElectricalRetinaHuman feasibilityHuman feasibility
WriteInvasiveElectricalCochleaEstablishedEstablished
WriteInvasiveElectricalBrainstemEstablishedEstablished
WriteInvasiveElectricalCortexEstablishedEarly human
WriteInvasiveElectricalCortexEarly humanEarly human
WriteInvasiveOptical, MolecularCortex, Deep brain, RetinaEarly humanPreclinical
WriteInvasiveElectricalDeep brainEstablishedEarly human
BidirectionalInvasiveElectricalPeripheral nerve, Muscle / neuromotorEarly humanEarly human
BidirectionalInvasiveElectricalCortexEstablishedEarly human
BidirectionalInvasiveElectricalCortex, Deep brainEstablishedHuman feasibility
BidirectionalInvasiveElectricalCortex, Spinal cordEarly humanEarly human
BidirectionalInvasiveElectricalCortexEarly humanEarly human
BidirectionalInvasiveElectricalDeep brain, CortexEstablishedEarly human
BidirectionalInvasiveElectricalDeep brainEstablishedHuman feasibility
BiohybridEx vivoElectrical, BiologicalCultured neural tissueAdjacent frontierAdjacent frontier
BiohybridEx vivoElectrical, Optical, BiologicalCultured neural tissueAdjacent frontierAdjacent frontier
BiohybridEx vivoBiological, ElectricalCultured neural tissueAdjacent frontierAdjacent frontier
BiohybridEx vivoBiological, ElectricalCultured neural tissueAdjacent frontierAdjacent frontier

Use-case explorer

Start from what people want to do

Nine human goals. Each one connects the technology, the companies, the research, the studies and the tools behind it, and says plainly what is available today.

Decoding attempted speech or writing into text and voice.

Can someone who cannot speak hold a conversation again?

Research participants with paralysis have used implanted BCIs to produce text and synthesised voice from attempted speech. All such systems remain in early feasibility studies.

Latest milestoneA single surface implant decoded speech and upper-body gestures at the same time in three participants.

Technology
EEGMEG / OPMEndovascularECoGIntracorticalsEEG
Companies
NeuralinkSynchronPrecision NeuroscienceParadromicsBlackrock NeurotechBrainGateStairMedNeuroXessNeuCyber NeuroTechABILITY NeurotechJiMEDg.tec medical engineeringArayaCognixion
Research
Simultaneous speech and gesture decoding for multimodal communication in paralysisAn Accurate and Rapidly Calibrating Speech NeuroprosthesisAn instantaneous voice-synthesis neuroprosthesisA high-performance speech neuroprosthesisA high-performance neuroprosthesis for speech decoding and avatar control+10 more
Clinical
VOICEConnect-OneBrainGate2BRAVOUNPCortiCom+3 more
Tools
BRANDtorch_brainimg_pipeMNE-PythonBraindecode
Datasets
Brain-to-Text '25Brain-to-Text Benchmark '24LibriBrain / LibriBrain100Podcast ECoG
Frontier
Speech & CommunicationCognitive Interfaces
On the calendar
BCI Meeting 2027

Why do such different devices exist for the same goal? Each trades signal quality against surgical access. Read the dossier