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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
Clinical ECoG grid
Layer 7
Neuropixels 1.0
Neural interfaces, measuredElectrode size and pitch at true scale, and where each interface sits, on the dura, under it or in the cortex, and how it gets there. Each square above is 1 mm of cortex.

32 interfaces

The interface map

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. 01The 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

BiohybridEx vivoBiological + Electrical

Biohybrid neural computing

Living neurons on a chip, connected in closed loop to a simulated or physical environment, used as part of a computing system. A peer-reviewed study in 2022 reported that cultured neurons changed their activity in a simplified game when given structured feedback. Whether that is learning is debated.

Showing Biohybrid neural computing: Biohybrid, Ex vivo.

Biohybrid · Adjacent frontierLiving neural tissue studied outside the body. It is not a brain-computer interface in a person, and nothing here is a treatment.

Where it acts
Neurons on a chip, wired to a simulated or robotic environment
Information flow
Environment ↔ living neurons
Living neuronsEnvironmentDecoded actionEncoded feedback
Fig. 02Where it acts, and which way information flowsSchematic, not to scale. Not a specific device.

How far it has come

As a clinical modality
Adjacent frontierEarly research systems. No demonstrated advantage over conventional computing on any practical task.
As a BCI application
Adjacent frontierNot a brain-computer interface: here the tissue is the computer, not the user.
Access
Ex vivo
Mechanism
Biological, Electrical
Target
Cultured neural tissue
Signal
Encoded task state in; decoded activity out

Characteristics · biohybrid interfaces

Input capabilityTask state encoded as stimulation patterns
Output capabilityActivity decoded into actions
AdaptabilityReported in simple tasks; interpretation debated
LongevityWeeks to months
ReproducibilityFew independent replications
ScalabilitySmall networks; keeping tissue alive is the bottleneck
Research maturityEarly

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

Strengths

  • A direct test bed for how living networks adapt to feedback
  • Gives disease and drug models a functional read-out

Trade-offs

  • No demonstrated advantage over conventional computing
  • Results depend on fragile, short-lived preparations

Common applications

  • Research on learning and adaptation
  • Drug and disease models
  • Laboratory demonstrations with simple robots

Human evidence

None in people.

What needs to happen next

Independent replication, benchmarks against simple artificial systems, and preparations that stay stable for longer.

Same site, other direction

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 things people want an interface to do. Each links the technology, the companies, the research, the studies and the tools behind it, and says 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 paralysisLong-term independent use of an intracortical brain–computer interface for speech and cursor controlImplanted brain-computer interface functionality during nighttime in late-stage amyotrophic lateral sclerosisAn Accurate and Rapidly Calibrating Speech NeuroprosthesisAn instantaneous voice-synthesis neuroprosthesis+13 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