{
  "id": "AIBD-0002",
  "title": "Intracortical speech neuroprosthesis restores conversation for a man with ALS (UC Davis, BrainGate2)",
  "summary": "Four 64-electrode arrays plus RNN decoder let Casey Harrell (ALS) converse at 97.5% accuracy; later 1.96 million words at home",
  "date_observed": "2023-08-01",
  "date_basis": "unassessed",
  "date_precision": "unassessed",
  "benefit_status": null,
  "source_collection": null,
  "source_entry": null,
  "account": "At the University of California Davis, a 45-year-old man with amyotrophic lateral sclerosis and severe dysarthria took part in the BrainGate2 trial (NCT00912041). Press identify him as Casey Harrell. Four 64-electrode arrays were implanted in his left precentral gyrus in July 2023. From August 2023, a decoder predicting phonemes every 80 ms, with language models over a 125,000-word vocabulary, converted his attempted speech to text. Accuracy was 99.6% with a 50-word vocabulary on day one and 90.2% with the full vocabulary on day two. It was 97.5% sustained over 248 hours of self-paced conversation with family, friends and colleagues (Card et al., NEJM, August 2024). The paper gives only the month for the first session, so 1 August 2023 is used.",
  "category": "benefit created",
  "unexpected": false,
  "purpose": "Built to restore communication by decoding attempted speech from intracortical activity into text. Conversational communication was the intended benefit and is what occurred.",
  "system": "UC Davis intracortical speech neuroprosthesis (BrainGate2 trial)",
  "model_version": "Four 64-electrode microelectrode arrays (256 electrodes) in the left precentral gyrus; phoneme decoder with an openly available language model assembling phonemes into words and two further open-source language models producing the sentence, over a 125,000-word vocabulary",
  "developer": "UC Davis Neuroprosthetics Lab (Brandman, Stavisky) with the BrainGate consortium",
  "deployer": "UC Davis Health",
  "location": "Davis, United States",
  "domain": "Healthcare / assistive communication",
  "segment": "ALS with severe dysarthria",
  "benefit_type": "Improved Accessibility",
  "taxonomy_note": null,
  "registry_ids": {
    "oecd_aim": "2026-06-15-4dfc"
  },
  "ratings": [
    {
      "group": "personal",
      "depth": 3,
      "reason": "Life-changing benefit to one identifiable person: conversational communication with family and colleagues was restored. The 2026 follow-up documents over 3,800 hours of unsupervised home use, nearly two million words and continued full-time employment."
    }
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  "ai_role": {
    "status": "assessed",
    "statement": "A neural-network decoder (phoneme prediction every 80 ms) combined with language models is the mechanism converting attempted speech into text. The benefit is attributable to the decoding system, with surgery and arrays as enabling hardware."
  },
  "evidence": [
    {
      "kind": "peer-reviewed study",
      "citation": "Card NS, Wairagkar M, Iacobacci C, et al. (2024). An Accurate and Rapidly Calibrating Speech Neuroprosthesis. N Engl J Med 391(7):609-618 (issue of 15 August 2024).",
      "title": "An Accurate and Rapidly Calibrating Speech Neuroprosthesis",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC11328962/",
      "date": "2024-08-15",
      "written_by": "makers",
      "quote": "With further training data, the neuroprosthesis sustained 97.5% accuracy for self-paced conversations for over 248 cumulative hours over 8.4 months after surgical implantation."
    },
    {
      "kind": "peer-reviewed study",
      "citation": "Card NS, Singer-Clark T, Peracha H, et al. (2026). Long-term independent use of an intracortical brain-computer interface for speech and cursor control. Nature Medicine.",
      "title": "Long-term independent use of an intracortical brain-computer interface for speech and cursor control",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC13375540/",
      "date": "2026-06-15",
      "written_by": "makers",
      "quote": "Over nearly 2 years, the participant used the BCI for more than 3,800 h at home with no researchers present."
    },
    {
      "kind": "news report",
      "citation": "Sanders L (2026). Brain implants are helping people who've lost their voice. Science News.",
      "title": "Brain implants are helping people who've lost their voice",
      "url": "https://www.sciencenews.org/article/brain-implants-restore-voices-injuries",
      "date": "2026-10-15",
      "written_by": "independent",
      "quote": "In 2023, Harrell had four small devices implanted on the left side of his brain."
    },
    {
      "kind": "press release",
      "citation": "UC Davis Health (2024). New brain-computer interface allows man with ALS to 'speak' again. Institutional release republished by ScienceDaily.",
      "title": "New brain-computer interface allows man with ALS to 'speak' again",
      "url": "https://www.sciencedaily.com/releases/2024/08/240814170129.htm",
      "date": "2024-08-14",
      "written_by": "makers",
      "quote": "To develop the system, the team enrolled Casey Harrell, a 45-year-old man with ALS, in the BrainGate clinical trial."
    }
  ],
  "replication": {
    "produced_by": [
      "Preserved speech-motor cortical activity during attempted speech despite severe dysarthria",
      "256-electrode intracortical recording in the ventral precentral gyrus",
      "Phoneme decoder plus large-vocabulary language models calibrated on the participant's own data within minutes",
      "Regulated trial setting (BrainGate2, NCT00912041) with ongoing research support"
    ],
    "must_hold": [
      "Array signal quality remains stable over months to years",
      "Participant retains the ability to attempt speech and the cognition to operate the system",
      "Decoder recalibration available as neural signals drift"
    ],
    "echoes": [
      {
        "date": "2025-06-12",
        "setting": "Same participant (T15), UC Davis: instantaneous voice synthesis from the same four 64-electrode arrays (256 electrodes), with neural processing from signal acquisition to speech synthesis within 10 ms, including intonation control and singing short melodies",
        "model_version": "Four 64-electrode arrays (256 electrodes); brain-to-voice model adapted from the Transformer architecture",
        "outcome": "recurred",
        "source": "Wairagkar M, Card NS, et al. (2025). An instantaneous voice-synthesis neuroprosthesis. Nature. https://pmc.ncbi.nlm.nih.gov/articles/PMC12369848/"
      },
      {
        "date": "2026-06-15",
        "setting": "Same participant, at-home independent use over nearly two years: 183,060 sentences, 1,960,163 words, 56 words per minute, full-time employment maintained",
        "model_version": null,
        "outcome": "recurred",
        "source": "Card NS, et al. (2026). Long-term independent use of an intracortical brain-computer interface for speech and cursor control. Nature Medicine. https://pmc.ncbi.nlm.nih.gov/articles/PMC13375540/"
      }
    ]
  },
  "paired_incident": {
    "database": "AI Incident Database",
    "identifier": "732",
    "title": "Whisper Speech-to-Text AI Reportedly Found to Create Violent Hallucinations",
    "url": "https://incidentdatabase.ai/cite/732",
    "severity": null,
    "group": "personal",
    "basis": "Both decode speech for people with impaired speech; Whisper fabricated words and violent phrases when transcribing impaired speech."
  },
  "headline": "UC Davis neuroprosthesis restores conversation for Casey Harrell",
  "metric": "97.5% sustained accuracy over 248 hours of self-paced conversation",
  "comparator": null,
  "later": {
    "status": "persisted",
    "date": "2026-06-15",
    "note": "A Nature Medicine report covering nearly two years of unsupervised home use found the same participant communicated 1,960,163 words at 56 words per minute and kept full-time employment.",
    "quote": "Over nearly 2 years, the participant used the BCI for more than 3,800 h at home with no researchers present to maintain rich interpersonal communication with his family and friends, independently control his personal computer and sustain full-time employment—despite being paralyzed.",
    "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC13375540/"
  },
  "value": null,
  "developer_country": "United States",
  "deployer_country": "United States",
  "unrated_because": null,
  "brief_notes": null,
  "brief": null,
  "revisions": [
    {
      "date": "2026-10-20",
      "change": "Record drafted from the cited sources.",
      "source": null,
      "editor": "AIBD"
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    {
      "date": "2026-10-20",
      "change": "Paired with AI Incident Database incident 732 (medium confidence); severity not given by the source.",
      "source": "https://incidentdatabase.ai/cite/732",
      "editor": "AIBD"
    },
    {
      "date": "2026-10-20",
      "change": "Replaced the placeholder NEJM date with the 15 August 2024 issue date, restored the full 97.5% sentence, recounted the language models as one word-assembling model plus two further sentence-level models as the paper describes, and verified the 10 ms, Transformer and same-participant (T15) details of the 2025 voice-synthesis echo against the full text at PMC and the cited 2026 Nature Medicine paper, which says T15's clinical status was previously reported in the NEJM paper.",
      "source": "https://pmc.ncbi.nlm.nih.gov/articles/PMC11328962/; https://pmc.ncbi.nlm.nih.gov/articles/PMC12369848/; https://pmc.ncbi.nlm.nih.gov/articles/PMC13375540/",
      "editor": "AIBD"
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    {
      "date": "2026-10-20",
      "change": "Linked the OECD AI Incidents entry, which describes this event.",
      "source": null,
      "editor": "AIBD"
    },
    {
      "date": "2026-10-21",
      "change": "Added what happened since from the cited sources.",
      "source": "https://pmc.ncbi.nlm.nih.gov/articles/PMC13375540/",
      "editor": "AIBD"
    },
    {
      "date": "2026-10-21",
      "change": "Country of the developer and the deployer added from the organization's own site or a registry.",
      "source": "https://en.wikipedia.org/wiki/University_of_California,_Davis; https://health.ucdavis.edu/about/",
      "editor": "AIBD"
    },
    {
      "date": "2026-10-21",
      "change": "Prose pass: a rating reason, account, purpose, the system's part rewritten in shorter sentences with abbreviations expanded; facts, figures and quotations unchanged.",
      "source": null,
      "editor": "AIBD"
    }
  ],
  "confidence": "reported",
  "shade": "medium",
  "claim_status": "Independently reported",
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            "account": "At the University of California Davis, a 45-year-old man with amyotrophic lateral sclerosis and severe dysarthria took part in the BrainGate2 trial (NCT00912041). Press identify him as Casey Harrell. Four 64-electrode arrays were implanted in his left precentral gyrus in July 2023. From August 2023, a decoder predicting phonemes every 80 ms, with language models over a 125,000-word vocabulary, converted his attempted speech to text. Accuracy was 99.6% with a 50-word vocabulary on day one and 90.2% with the full vocabulary on day two. It was 97.5% sustained over 248 hours of self-paced conversation with family, friends and colleagues (Card et al., NEJM, August 2024). The paper gives only the month for the first session, so 1 August 2023 is used.",
            "replication": {
              "produced_by": [
                "Preserved speech-motor cortical activity during attempted speech despite severe dysarthria",
                "256-electrode intracortical recording in the ventral precentral gyrus",
                "Phoneme decoder plus large-vocabulary language models calibrated on the participant's own data within minutes",
                "Regulated trial setting (BrainGate2, NCT00912041) with ongoing research support"
              ],
              "must_hold": [
                "Array signal quality remains stable over months to years",
                "Participant retains the ability to attempt speech and the cognition to operate the system",
                "Decoder recalibration available as neural signals drift"
              ],
              "echoes": [
                {
                  "date": "2025-06-12",
                  "setting": "Same participant (T15), UC Davis: instantaneous voice synthesis from the same four 64-electrode arrays (256 electrodes), with neural processing from signal acquisition to speech synthesis within 10 ms, including intonation control and singing short melodies",
                  "model_version": "Four 64-electrode arrays (256 electrodes); brain-to-voice model adapted from the Transformer architecture",
                  "outcome": "recurred",
                  "source": "Wairagkar M, Card NS, et al. (2025). An instantaneous voice-synthesis neuroprosthesis. Nature. https://pmc.ncbi.nlm.nih.gov/articles/PMC12369848/"
                },
                {
                  "date": "2026-06-15",
                  "setting": "Same participant, at-home independent use over nearly two years: 183,060 sentences, 1,960,163 words, 56 words per minute, full-time employment maintained",
                  "outcome": "recurred",
                  "source": "Card NS, et al. (2026). Long-term independent use of an intracortical brain-computer interface for speech and cursor control. Nature Medicine. https://pmc.ncbi.nlm.nih.gov/articles/PMC13375540/"
                }
              ]
            }
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      "addressed": 91,
      "known": 36,
      "reviewed": 0,
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      "not_assessed": 55,
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}