The thought translation device: a neurophysiological approach to communication in total motor paralysis

A thought translation device (TTD) for brain-computer communication is desc ribed. Three patients diagnosed with amyotrophic lateral sclerosis (ALS), w ith total motor paralysis, were trained for several months. In order to ena ble such patients to communicate without any motor activity, a technique wa s developed where subjects learn to control their slow cortical potentials (SCP) in a 2-s rhythm, producing either cortical negativity or positivity a ccording to the task requirement. SCP differences between a baseline interv al, and an active control interval are transformed into vertical or horizon tal cursor movements on a computer screen. Learning SCP self regulation fol lowed an operant-conditioning paradigm with individualized shaping procedur es. After prolonged training over more than 100 sessions, all patients achi eved self-control, leading to a 70-80% accuracy for two patients. The learn ed cortical skill enabled the patients to select letters or words in a lang uage-supporting program (LSP) developed for inter-personal communication. T he results demonstrate that the fast and stable SCP self-control can be ach ieved with operant training and without mediation of any muscle activity. T he acquired skill allows communication even in total locked-in states.