Development of speech prostheses: current status and recent advances.

[locked-in syndrome]

Brain -computer interfaces (BCIs ) have been developed over the past decade to restore communication to persons with severe paralysis . In the most severe cases of paralysis , known as locked-in syndrome , patients retain cognition and sensation , but are capable of only slight voluntary eye movements . For these patients , no standard communication method is available , although some can use BCIs to communicate by selecting letters or words on a computer . Recent research has sought to improve on existing techniques by using BCIs to create a direct prediction of speech utterances rather than to simply control a spelling device . Such methods are the first steps towards speech prostheses as they are intended to entirely replace the vocal apparatus of paralyzed users . This article outlines many well known methods for restoration of communication by BCI and illustrates the difference between spelling devices and direct speech prediction or speech prosthesis .