Skip to content
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

ReadNon-invasiveElectrical

Electroencephalography

Electrodes on the scalp record the summed electrical activity of large neural populations through the skull.

Showing Electroencephalography: Read, Non-invasive.

Where it acts
On the scalp
Information flow
Brain → scalp electrodes
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
EstablishedA routine clinical test for epilepsy, sleep and brain monitoring.
As a BCI application
Human feasibilityDecades of human studies and consumer products. Few validated clinical uses as an interface.
Access
Non-invasive
Mechanism
Electrical
Target
Cortex
Signal
Summed field potentials, blurred and attenuated by skull and scalp

Characteristics · read interfaces

Spatial resolutionCentimetre scale
Temporal resolutionMilliseconds
Signal richnessThe summed activity of large populations
CoverageWhole head
InvasivenessNone
Long-term stabilityVaries session to session

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

Strengths

  • No surgery
  • Low cost and portable
  • Largest open tooling and dataset ecosystem

Trade-offs

  • Low signal-to-noise for fine movement or speech
  • Sensitive to setup, movement and muscle artefacts

Common applications

  • Clinical monitoring
  • Rehabilitation and neurofeedback research
  • Consumer wearables

Human evidence

Very large human literature. Reliable for coarse control and brain-state monitoring; decoding of speech or fine movement remains limited. As therapy it has gone furthest: an EEG system for hand rehabilitation after stroke has held FDA marketing authorisation since 2021.

What needs to happen next

Dry, wearable sensors that hold signal quality outside the laboratory, and decoders that transfer between people and sessions.

Used by
BrainCog.tec medical engineeringKanduArayaCognixionNGoggle
Research
MEG and EEG data analysis with MNE-Python
Tools
UltracortexOpenBCI GUIBrainFlowMNE-CPPLab Streaming LayerMNE-LSL+9 more
Datasets
BNCI 2014-001 (BCI Competition IV 2a)EEG Motor Movement/Imagery
Use cases
ControlMonitorAugmentCommunicate
On the calendar
BCI Meeting 2027
Patent activity
3,612 patent families name this interface, most often on neural decoding, signal processing, motor 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