A longitudinal study of traumatic brain-injured and comatose participants suggests that these individuals are able to learn to use a mental interface device to navigate a maze and perform some basic communication. The device, known as the "Cyberlink", uses electrooculargraphic, electromyographic, and electroencephlagraphic signals collected at the forehead to control cursor movement. Further details of the operation of the device and the set-up procedures are reported. Six adults, all of whom had traumatic brain injury or were believed to be comatose, participated in the study over a 7-month period. Initially, only one participant, who had previously used the device, could navigate the maze. At the end of the study all participants could navigate the maze, albeit with a high variability in success rate. Reasons for the variability obtained are postulated. The majority of participants could also use the device to type simple words. Positive behaviors and increases in attention span were also observed. The diagnosis of one participant was upgraded from coma to traumatic brain stem injury as a result of data collected during the study. Controls were built into the study in order to demonstrate intention. Further developments of the device and other applications where it may be useful are discussed.