Are you having difficulty falling asleep? Try drinking a glass of warm milk. If that doesn't work, listen to some soft, beautiful music. Still no luck? Try think about sheep jumping over a fence. If you are still awake, take a sleeping pill. People who take pills often become dependent on the drugs. So you lie awake knowing that the new workday will soon arrive. If you have been in such condition for at least one month, you may have primary insomnia . A new study has found that you might fall asleep more quickly and stay asleep longer if you try "cerebral hypothermia." It is not a complex medical process. It just means cooling down your brain. Eric Nofzinger and Naniel Buysse from the University of Pittsburgh Medical School led the study. They examined twelve people who had sleeping problems. Twelve others had no sleeping problems. Each of them wore a soft plastic cap on their head at bedtime. The caps had tubes inside filled with water. The researchers moved the water through the tubes and then changed the temperature of the water. Other studies showed that people who had sleeping problems often had more chemical reactions in the front of their brain. The researchers thought cooling down the brain might help. On the first two nights of testing, the patients wore caps with no water. On the next two nights, the caps were worn, but the water was not cooled. Then the researchers cooled the water a little for another two nights. On the final two nights of the study, the temperature of the water was made much cooler. The researchers found that the water caps didn' t help the patients until the temperature was about 14degC. Most of the patients fell asleep faster and slept better when the coolest water was moving around their head.  Dr Nfzinger and Dr. Buysse noted that this was only the beginning of the brain temperature study. But they believed they had discovered something important that needed more research. From the passage we know that "cerebral hypothermia" is actually   _  .
a complex medical process. a psychological treatment. a difficult scientific theory. a simple physical treatment.