BrainGate2 clinical trial (speech neuroprosthesis) by BrainGate consortium: status and timeline

Milestones

Next · UC Davis speech trial recruiting

First BrainGate trial initiated (original)2004Complete.
FDA approves BrainGate2 IDEJul 2009Complete.
Stanford joins BrainGate2 consortiumNov 2011Complete.
First 3D robotic arm control by tetraplegia patients2012Complete.
ALS patient achieves 97% speech decoding accuracyAug 2024Complete.
Inner speech decoding published in Cell2025Complete.
UC Davis speech trial recruitingTarget Aug 2022Current milestone.

Most important updates

Upcoming

Aug 2022UC Davis speech trial recruiting (next)
2027Neurorehabilitation outcomes from participants
2027FDA breakthrough device designation for speech BCI

Current obstacles

Surgical implantation riskPlacing electrodes in motor cortex requires invasive surgery with associated risks, limiting adoption to severely disabled patients.
Neural signal driftElectrode impedance and neural activity can change over months, requiring repeated calibration of the decoding model.
Scaling to naturalistic communicationMost trials demonstrate accurate decoding in controlled settings; real-world, continuous communication without performance degradation remains challenging.

Physics limits

Motor cortex representationSpeech is represented in Broca's area and Wernicke's area in the language-dominant hemisphere; motor cortex implants capture intended movement signals that correlate with speech intent, not direct linguistic encoding.
Device longevityImplanted electrodes can lose signal quality over years; foreign-body response and electrode degradation may limit device lifespan to 5-10 years or longer.
Vocabulary ceilingDecoding individual words is feasible; decoding syntax, grammar, and nuanced meaning from motor cortex signals alone may require additional recording sites or hybrid approaches.

How it works

4 parts

Implantation

Utah arrays

Four electrode arrays implanted in motor cortex record signals from 96 electrodes per array.

Signal decoding

Machine learning

Algorithms analyze neural firing to identify intended words or movements learned from training.

Output

Speech synthesis

Decoded words become audio via text-to-speech, customizable to sound like pre-illness voice.

Robotic control

Device operation

Decoded signals operate robotic arms for reaching, grasping, and manipulation in 3D space.

Spec sheet

Spec	BrainGate2 clinical trial (speech neuroprosthesis)
Electrodes per microelectrode array	96 (baby aspirin-sized)^R (reported)
Speech decoding accuracy (ALS)	Up to 97% in conversation^R (reported)
Inner speech decoding accuracy	Up to 74%^R (reported)
Vocabulary size (Casey Harrell trial)	More than 125,000 words^R (reported)
Time to communication (UC Davis trial)	Within minutes of system activation^R (reported)

^R reported by the company

Update log

4 updates

About BrainGate consortium

The team behind BrainGate2 clinical trial (speech neuroprosthesis)

BrainGate consortium

brain-computer interface, paralysis, speech, ALS

Multi-institutional research consortium developing implantable brain-computer interfaces to restore communication and assistive device control for paralyzed patients.

Company profile →

Headquarters: United States
Status: Non-profit
Valuation: non-profit
Works in: NeurotechBrain implants
Coverage: 2 programs · 7 updateslatest 1 Aug 2026checked 11 Oct
People: Leigh HochbergDirectorDavid BrandmanresearcherSergey Staviskyresearcher

Spec

BrainGate2 clinical trial (speech neuroprosthesis)

Electrodes per microelectrode array

96 (baby aspirin-sized)^R (reported)

Speech decoding accuracy (ALS)

Up to 97% in conversation^R (reported)

Inner speech decoding accuracy

Up to 74%^R (reported)

Vocabulary size (Casey Harrell trial)

More than 125,000 words^R (reported)

Time to communication (UC Davis trial)

Within minutes of system activation^R (reported)

BrainGate2 clinical trial (speech neuroprosthesis)

Milestones

Most important updates

Upcoming

Current obstacles

Physics limits

How it works

Utah arrays

Machine learning

Speech synthesis

Device operation

Spec sheet

Update log

Feb 2026

2025

Aug 2024

2022

About BrainGate consortium

Current obstacles

Physics limits

How it works

Utah arrays

Machine learning

Speech synthesis

Device operation

Spec sheet

Update log

Feb 2026

2025

Aug 2024

2022

About BrainGate consortium