Brain-computer interfaces for communication with nonresponsive patients.

A substantial number of patients who survive severe brain injury progress to a nonresponsive state of wakeful unawareness, referred to as a vegetative state (VS). They appear to be awake, but show no signs of awareness of themselves, or of their environment in repeated clinical examinations. However, recent neuroimaging research demonstrates that some VS patients can respond to commands by willfully modulating their brain activity according to instruction. Brain-computer interfaces (BCIs) may allow such patients to circumvent the barriers imposed by their behavioral limitations and communicate with the outside world. However, although such devices would undoubtedly improve the quality of life for some patients and their families, developing BCI systems for behaviorally nonresponsive patients presents substantial technical and clinical challenges. Here we review the state of the art of BCI research across noninvasive neuroimaging technologies, and propose how such systems should be developed further to provide fully fledged communication systems for behaviorally nonresponsive populations.