Doctors call this study a polysomnogram. It charts your brain waves, heart beat, and breathing as you sleep. It also records your eye and leg movements as well as muscle tension. Sensors are placed on your head, face, chest and legs. They send tiny electrical signals to a computer.

The signals show when you are asleep and awake during the night. The brain-wave and eye-movement detectors show when you are in REM sleep. This stands for rapid eye movement sleep. This is a stage of sleep where your eyes twitch and your brain waves are very active. It is also the stage of sleep when you have most of your dreams.

The breathing monitors show the number of times you stop breathing. They can also detect low air flow and minor changes in oxygen level.

The leg sensors show both minor twitches and major movements that occur during the night.

A clip will also be placed on your finger to note changes in the level of oxygen in your blood. The clip monitors the color of your blood. As blood loses oxygen, it turns from red to blue.

You will be asked to come to the center in the evening. Some time will be given for you to make yourself at home in the bedroom. No other patients will be in the room with you.

You will not feel any pain during the polysomnogram. The sensors are gently placed on your skin and connected to a computer. The wires are long enough to let you move around and turn over in bed. You will be asked to move your eyes, clench your teeth and move your legs. This will make sure that the sensors are working.

You are free to read or watch TV until your normal bedtime. Then the lights are turned out and it is time for you to try to fall asleep. A low-light video camera allows a technologist to see you from a nearby room. He or she will have to enter your room if a sensor comes loose. He or she will also have to detach the wires if you need to go to the bathroom during the night.

The polysomnogram is not a test that you can fail. Nearly everyone falls asleep during the study. Most people do not sleep as well as they do at home. This will not affect the results. In most cases, you do not need to sleep for a full eight hours to find the source of your problem.