Grace has just been diagnosed with Alzheimer's disease. Grace has a major type of a general category of problem known as:

In one study, 8 volunteers reduced their sleep by 30 minutes per night until they did not want to reduce it further. A major finding was that

A) 4 managed to reduce their sleep to 5 hours per night. B) 2 managed to reduce their sleep to 4.5 hours per night. C) the volunteers began to experience significant daytime sleepiness once they had reduced their sleep to 6 hours or less per night. D) the volunteers were still sleeping between 7 and 18 hours less per week when they were tested 1 year after the experiment ended. E) all of the above

Somnambulism usually occurs during stage __________ sleep

Fill in the blank with the appropriate word.