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

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.

AccessMechanismTargetMaturityUse case

32 interfaces

Access ↓

Read

Sense neural activity

Bidirectional

Sense and stimulate in closed loop

Write

Influence neural activity

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 spaceSelect up to 4 interfaces to compare.

Colour · function

Read
Write
Bidirectional
Biohybrid

Fill · maturity as a clinical modality

Established
Human feasibility
Early human
Preclinical
Research frontier
Adjacent frontier

ComparingCochlear · ABI

Compare mode

Two to four, side by side

Select interfaces on the map, or start from a pairing that answers a common question. Only characteristics that apply to every interface chosen are compared.

Add from the map

Useful comparisons

Comparison of Cochlear implants, Auditory brainstem implants
Dimension
Function	WriteInfluence neural activity	WriteInfluence neural activity
Access	InvasiveEar surgery, outside the skull.	InvasiveOpen surgery at the brainstem, often in the same operation that removes a tumour.
Mechanism	Electrical	Electrical
Target	Cochlea	Brainstem
Information flow	Electrode array → auditory nerve	Electrode paddle → cochlear nucleus
Spatial precisionCentimetres → Single neurons	Tens of channels, blurred by current spread	Few channels that carry distinct pitch
TargetabilityUnselective → Cell-type specific	Frequency regions along the cochlea	A small target; placement varies between patients
CoverageOne small site → Whole brain	Most of the range used for speech	Sound awareness for most, open speech for some
InvasivenessNone → Open, penetrating	Ear surgery	Open surgery at the brainstem
Maturity as a clinical modality	EstablishedRoutine care for severe hearing loss, for decades.	EstablishedAuthorised in the United States since 2000 for deafness from neurofibromatosis type 2; more than 1,000 implanted worldwide.
Maturity as a BCI application	EstablishedThe reference case for a neural interface in everyday use.	EstablishedIn clinical use for a small group of patients. It writes sound and reads nothing, and its results are modest beside the cochlear implant's.
Strengths	Decades of evidence and routine clinical pathways Speech understanding for most recipients	Works where there is no usable cochlea or auditory nerve Authorised for one indication since 2000, with long clinical experience
Limitations	Coarse pitch: music and speech in noise remain hard Outcomes vary widely between people	Modest speech understanding: about a fifth of open-set sentences in tumour patients, pooled across studies Results vary widely, and electrode placement is hard to control
Common applications	Severe to profound hearing loss	Deafness from neurofibromatosis type 2 People from 12 months of age whose auditory nerve does not work, under one maker's CE mark in Europe; children in the United States only in studies
Human evidence	Extensive: routine care in children and adults, with long-term outcome data.	A 2024 systematic review pooled 662 recipients with tumours and 267 without: open-set sentence understanding averaged 21.5% in the first group and 53.0% in the second. Most recipients gain awareness of sound and help with lip-reading.
What needs to happen next	Finer pitch through more independent channels. Light-based stimulation is one route, and is preclinical.	Arrays that conform to the brainstem, electrodes that penetrate it and light-based stimulation are in development. Children without an auditory nerve are the group now under study.
Related research	None in our corpus yet	None in our corpus yet
Related companies	MED-EL Cochlear	MED-EL Cochlear

Bars run from low to high and show a range, not a score. A wide bar means the characteristic varies across implementations. Qualitative editorial ranges; specific devices differ.

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
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 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: EEG MEG / OPM Endovascular ECoG Intracortical sEEG
Companies: Neuralink Synchron Precision Neuroscience Paradromics Blackrock Neurotech BrainGate StairMed NeuroXess NeuCyber NeuroTech ABILITY Neurotech JiMED g.tec medical engineering Araya Cognixion
Research: Simultaneous speech and gesture decoding for multimodal communication in paralysis Long-term independent use of an intracortical brain–computer interface for speech and cursor control Implanted brain-computer interface functionality during nighttime in late-stage amyotrophic lateral sclerosis An Accurate and Rapidly Calibrating Speech Neuroprosthesis An instantaneous voice-synthesis neuroprosthesis+13 more
Clinical: VOICE Connect-One BrainGate2 BRAVO UNP CortiCom+3 more
Tools: BRAND torch_brain img_pipe MNE-Python Braindecode
Datasets: Brain-to-Text '25 Brain-to-Text Benchmark '24 LibriBrain / LibriBrain100 Podcast ECoG
Frontier: Speech & Communication Cognitive 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

The interface map