Brain-computer communication: self-regulation of slow cortical potentials for verbal communication.

OBJECTIVE

To test a training procedure designed to enable severely paralyzed patients to communicate by means of self-regulation of slow cortical potentials.

DESIGN

Application of the Thought Translation Device to evaluate the procedure in patients with late-stage amyotrophic lateral sclerosis (ALS).

SETTING

Training sessions in the patients' homes.

PARTICIPANTS

Two male patients with late-stage ALS.

INTERVENTIONS

Patients learned voluntary control of their slow cortical potentials by means of an interface between the brain and a computer. Training was based on visual feedback of slow cortical potentials shifts and operant learning principles. The learning process was divided into small steps of increasing difficulty.

MAIN OUTCOME MEASURES

Accuracy of self-control of slow cortical potentials (percentage of correct responses). Learning progress calculated as a function of training session.

RESULTS

Within 3 to 8 weeks, both patients learned to self-regulate their slow cortical potentials and to use this skill to select letters or words in the Language Support Program.

CONCLUSIONS

This training schedule is the first to enable severely paralyzed patients to communicate without any voluntary muscle control by using self-regulation of an electroencephalogram potential only. The protocol could be a model for training patients in other brain-computer interface techniques.