Classification of intended phoneme production from chronic intracortical microelectrode recordings in speech-motor cortex.

[locked-in syndrome]

We conducted a neurophysiological study of attempted speech production in a paralyzed human volunteer using chronic microelectrode recordings . The volunteer suffers from locked-in syndrome leaving him in a state of near-total paralysis , though he maintains good cognition and sensation . In this study , we investigated the feasibility of supervised classification techniques for prediction of intended phoneme production in the absence of any overt movements including speech . Such classification or decoding ability has the potential to greatly improve the quality-of-life of many people who are otherwise unable to speak by providing a direct communicative link to the general community . We examined the performance of three classifiers on a multi-class discrimination problem in which the items were 38 American English phonemes including monophthong and diphthong vowels and consonants . The three classifiers differed in performance , but averaged between 16 and 21 % overall accuracy (chance-level is 1 /38 or 2 .6 %). Further , the distribution of phonemes classified statistically above chance was non-uniform though 20 of 38 phonemes were classified with statistical significance for all three classifiers . These preliminary results suggest supervised classification techniques are capable of performing large scale multi-class discrimination for attempted speech production and may provide the basis for future communication prostheses .