A middle-aged man complains of lack of sleep during the night time. The duration of the time he is truly asleep or awake can be asceained by which of the following?

Actigraphy is the procedure which is used for studying the sleep patterns. It usually involves wearing a small sensor on the wrist, which detects the movements. However, the gold standard technique for studying sleep disorder is polysomnography. Barograph measure changes in atmospheric pressure which is recorded on cha paper. Kymograph is used for recording variations in pressure. Plethysmography is used for measuring variation in volume of organ of body.