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.
- Reading
- Writing
- Closed loop
- 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.
Colour · function
- Read
- Write
- Bidirectional
- Biohybrid
Fill · maturity as a clinical modality
- Established
- Human feasibility
- Early human
- Preclinical
- Research frontier
- Adjacent frontier
BidirectionalInvasiveElectrical
ECoG, recording and stimulating
The same surface grid records cortical activity and stimulates the cortex beneath it. Surgeons already do both in turn during mapping. The open question is doing both continuously in one long-term implant, and at much higher density with new electrode materials.
Showing ECoG, recording and stimulating: Bidirectional, Invasive.
- Where it acts
- On the cortical surface
- Information flow
- Cortex ↔ surface grid
How far it has come
- As a clinical modality
- EstablishedRecording and stimulating through the same grids is routine in epilepsy surgery.
- As a BCI application
- Early humanClosed-loop use in a long-term surface implant is at the stage of first studies.
- Access
- Invasive
- Mechanism
- Electrical
- Target
- Cortex
- Signal
- Field potentials out; electrical pulses in
Characteristics · bidirectional interfaces
- Recording qualityField potentials at millimetre scale
- Stimulation precisionMillimetres of cortex per contact
- Closed-loop latencyTens of milliseconds
- CoverageSeveral cm² per array
- InvasivenessOpening in the skull; no penetration
- Long-term stabilityRecording is stable for years; long-term stimulation data are sparse
Each track runs from low to high. A wide bar means the characteristic varies across implementations.
Strengths
- One implant for both directions, without penetrating cortex
- Stable recordings to drive the loop
Trade-offs
- Stimulation is coarse compared with electrodes inside the cortex
- Stimulation artefacts make it hard to record and stimulate at the same moment
Common applications
- Functional mapping
- Closed-loop therapy research
- Stroke rehabilitation research
Human evidence
Routine in mapping, where recording and stimulation alternate. Continuous closed-loop use in a long-term surface implant is limited to early studies.
What needs to happen next
Recording during stimulation without artefacts, and long-term human data from high-density thin-film and graphene arrays.
- Same site, other direction
- Clinical
- MRPICSINTENSE-BCI
- Patent activity
- 140 patent families name this interface, most often on electrodes and arrays, signal processing, 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
| Interface | Function | Access | Mechanism | Target | Clinical modality | BCI application |
|---|---|---|---|---|---|---|
| Read | Non-invasive | Electrical | Cortex | Established | Human feasibility | |
| Read | Non-invasive | Magnetic | Cortex | Established | Research frontier | |
| Read | Non-invasive | Optical | Cortex | Human feasibility | Research frontier | |
| Read | Non-invasive | Electrical | Muscle / neuromotor | Established | Established | |
| Read | Minimally invasive | Electrical | Cortex | Human feasibility | Human feasibility | |
| Read | Minimally invasive | Acoustic | Cortex, Deep brain | Early human | Preclinical | |
| Read | Invasive | Electrical | Peripheral nerve, Muscle / neuromotor | Early human | Early human | |
| Read | Invasive | Electrical | Cortex | Established | Human feasibility | |
| Read | Invasive | Electrical | Cortex | Human feasibility | Human feasibility | |
| Read | Invasive | Electrical | Deep brain, Cortex | Established | Early human | |
| Write | Non-invasive | Magnetic | Cortex | Established | Research frontier | |
| Write | Non-invasive | Electrical | Cortex | Human feasibility | Research frontier | |
| Write | Non-invasive | Acoustic | Cortex, Deep brain | Early human | Research frontier | |
| Write | Invasive | Electrical | Peripheral nerve | Established | Early human | |
| Write | Invasive | Electrical | Retina | Human feasibility | Human feasibility | |
| Write | Invasive | Electrical | Cochlea | Established | Established | |
| Write | Invasive | Electrical | Brainstem | Established | Established | |
| Write | Invasive | Electrical | Cortex | Established | Early human | |
| Write | Invasive | Electrical | Cortex | Early human | Early human | |
| Write | Invasive | Optical, Molecular | Cortex, Deep brain, Retina | Early human | Preclinical | |
| Write | Invasive | Electrical | Deep brain | Established | Early human | |
| Bidirectional | Invasive | Electrical | Peripheral nerve, Muscle / neuromotor | Early human | Early human | |
| Bidirectional | Invasive | Electrical | Cortex | Established | Early human | |
| Bidirectional | Invasive | Electrical | Cortex, Deep brain | Established | Human feasibility | |
| Bidirectional | Invasive | Electrical | Cortex, Spinal cord | Early human | Early human | |
| Bidirectional | Invasive | Electrical | Cortex | Early human | Early human | |
| Bidirectional | Invasive | Electrical | Deep brain, Cortex | Established | Early human | |
| Bidirectional | Invasive | Electrical | Deep brain | Established | Human feasibility | |
| Biohybrid | Ex vivo | Electrical, Biological | Cultured neural tissue | Adjacent frontier | Adjacent frontier | |
| Biohybrid | Ex vivo | Electrical, Optical, Biological | Cultured neural tissue | Adjacent frontier | Adjacent frontier | |
| Biohybrid | Ex vivo | Biological, Electrical | Cultured neural tissue | Adjacent frontier | Adjacent frontier | |
| Biohybrid | Ex vivo | Biological, Electrical | Cultured neural tissue | Adjacent frontier | Adjacent 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.
- 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
- 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