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
WriteInvasiveElectrical
Cortical surface stimulation
Electrodes on the surface of the brain pass current into the cortex beneath. Surgeons use it to map function. Researchers use it to evoke sensations, including patterns of light for people who are blind.
Showing Cortical surface stimulation: Write, Invasive.
- Where it acts
- On the cortical surface, above or below the dura
- Information flow
- Surface electrodes → cortex
How far it has come
- As a clinical modality
- EstablishedRoutine for mapping function during brain surgery.
- As a BCI application
- Early humanEvoked visual and touch percepts in individual research participants.
- Access
- Invasive. Stimulators seated in the skull above the dura reach the cortex without opening it, and are classed as minimally invasive in the company profiles.
- Mechanism
- Electrical
- Target
- Cortex
- Signal
- Electrical pulses through surface contacts
Characteristics · write interfaces
- Spatial precisionMillimetres of cortex per contact
- Temporal precisionMillisecond pulses
- Penetration depthThe cortical surface
- TargetabilityThe patch under each contact
- CoverageSeveral cm² per array
- InvasivenessOpening in the skull; no penetration
- ReversibilityStops when switched off; the array stays
Each track runs from low to high. A wide bar means the characteristic varies across implementations.
Strengths
- Does not penetrate cortex
- One array covers a wide area
Trade-offs
- Each contact activates a large population
- Needs higher currents than electrodes inside the cortex
Common applications
- Functional mapping in surgery
- Visual prosthesis research
- Therapeutic stimulation research
Human evidence
Routine in surgical mapping. As a way to write information, evidence comes from individual participants, for example shapes traced on visual cortex.
What needs to happen next
Denser arrays and stimulation patterns that produce stable, useful percepts over years.
- Same site, other direction
- Used by
- Motif Neurotech
- Clinical
- RESONATE
- Patent activity
- 240 patent families name this interface, most often on stimulation, electrodes and arrays, closed loop. 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