The difficulty is that most people do not stay in this transitional period for long. With my colleagues Johann Stoyva, Kirk Peffer, and Pola Sittenfeld, I taught subjects to maintain a twilight state in the laboratory. By learning to relax those muscles, they decrease cortical and autonomic arousal as well. Once they learn to produce theta brain waves, they can be trained to maintain the theta pattern indefinitely with a device called a Twilight Learner. Developed with the aid of John Picchiottino, an engineering consultant, the unit enables a trainee to maintain a twilight state as information from a cassette tape recorder is presented to him.
Sensors placed on the trainee's scalp pick up the tiny brain-wave signals.
When the trainee produces the theta pattern characteristic of the twilight state, the signal automatically turns on the tape recorder. As long as he produces theta, the tape recorder runs. If his brain waves change to alpha or beta, indicting an increase in alertness and a marshaling of critical cognitive faculties, the recorder shuts off. When this happens, the increased volume gently nudges the trainee back into twilight sleep. Beginning trainees often find themselves oscillating between an alert alpha pattern and a sleep theta pattern.