Comprehensive Summary
This review summarizes recent progress and future challenges of implantable neural speech decoders as a technology for restoring communication in locked-in syndrome (LIS) patients. The authors review over a decade of invasive brain–computer interface (BCI) research, including findings from high-profile clinical trials at UCSF, Stanford, and BrainGate, on the translation of neural signals recorded from speech motor cortex into communicable language. The key results show rapid gains in decoding rates and accuracy, with current systems achieving less than 3% word error rates and speech output at up to 78 words per minute, along with recent reports of real-time streaming with prosody and intonation. The review also addresses technical and design considerations, including optimal cortical target locations, linguistic representation levels, electrode instruments (microelectrode arrays, ECoG, stentrodes), and the requirement for closed-loop systems in order to maximize fluency. When discussing, the authors identify usability concerns, patient selection, and ethical concerns such as privacy, consent, and the potential to inadvertently decode inner speech.
Outcomes and Implications
This study is significant because it shows that neural speech decoders are realistic options for restoring efficient, natural communication for paralyzed patients with ALS or brainstem stroke who are currently using slow, effortful assistive devices. Clinically, invasive methods have been shown to be substantially better than non-invasive approaches which makes safety, surgical candidacy, and device stability critical for future implementation. The results further identify supervised, that user-directed design like integrating the patient for input, adaptive methods, caregiver usability will be key to adoption in natural contexts. While general use is still several years away, rapidity of advancements in technology, deep learning, and new implantable technology like high density ECoG and Neuralink will make functional neural speech prostheses a reality from research to early clinical steps within the next decade. However, ethical mechanisms for privacy protections, autonomy, and agency will have to adapt alongside to deal with timelines for responsible utilization with neurorehabilitation and clinical care.