# Locked-In Syndrome **Entity class:** Clinical condition and interface boundary **Domain:** Neurology / Assistive Communication / Brain-Computer Interfaces **Doc Type:** Canonical Clinical Concept Node **Maturity:** Established clinical category with contested boundaries **Primary source article:** [[articles/The Closed-Loop Gaussian Sensorium Engine|The Closed-Loop Gaussian Sensorium Engine]] **Collection:** [[collections/Neurotech|Neurotech]] --- ## Definition **Locked-in syndrome (LIS)** describes preserved consciousness and cognition with profound loss of voluntary motor output, commonly while some vertical eye movement or blinking remains available for communication. **Complete locked-in syndrome (CLIS)** is used when reliable eye or other muscle-based communication is also absent. The diagnostic boundary requires care. The 2022 Nature Communications case used behavioral, physiological, family, and device evidence to classify one participant with advanced ALS as completely locked-in, while also stating that no universally accepted clinical definition separates LIS from CLIS and that more sensitive measurement could reveal residual voluntary control. ## Interface significance LIS makes the difference between interior state and observable output clinically concrete. Assistive switches, eye tracking, auditory neurofeedback, and invasive BCIs do not create the person they reveal; they provide channels through which an existing person can become externally legible and exercise agency. The condition is therefore a boundary case for [[wiki/Brain-Computer Interfaces|Brain-Computer Interfaces]], [[wiki/Assistive Technology|Assistive Technology]], informed consent, withdrawal, caregiver interpretation, and the risk of confusing failed communication with absent cognition. ## Relationships - **Clinical route into:** [[wiki/Closed-Loop BCI|Closed-Loop BCI]] and [[wiki/Neural Decoding|Neural Decoding]]. - **Authorial frame:** [[wiki/Locked-In Inversion|Locked-In Inversion]]. - **Architecture informed by the frame:** [[wiki/Closed-Loop Gaussian Sensorium Engine|Closed-Loop Gaussian Sensorium Engine]]. - **Biographical route:** [[wiki/Stephen Hawking|Stephen Hawking]]; his late-life condition approached the interface problem without being identified in the source article as strict CLIS. - **Rights route:** [[wiki/Cognitive Liberty|Cognitive Liberty]], [[wiki/Neurorights|Neurorights]], and [[wiki/Perceptual Sovereignty|Perceptual Sovereignty]]. ## Sources and provenance - [[articles/The Closed-Loop Gaussian Sensorium Engine|The Closed-Loop Gaussian Sensorium Engine]] — article context and locked-in inversion. - [Chaudhary et al., “Spelling interface using intracortical signals in a completely locked-in patient enabled via auditory neurofeedback training” (Nature Communications, 2022)](https://www.nature.com/articles/s41467-022-28859-8) — primary clinical case and diagnostic caveats.