4. Imagine that you are a research assistant in a sleep laboratory. You are required to keep a log of sleeping participants' brain, physiological, and general body activity over the course of the night. Describe what you might expect to include in your log over the first 2 hours of the night.

A sleep cycle lasts about ninety minutes, with four to five cycles occurring in a night sleep period.

In the first hours we can analyze two cycles.

Stage 1

It starts with a drowsiness. It lasts approximately five minutes. The person falls asleep. It is characterized by an EEG similar to that of the waking state. This stage lasts from one to two minutes, and the individual is easily awakened. Wandering sensations, uncertain thoughts, myoclonus of the hands and feet, slow contraction and pupillary dilation predominate. In this phase, dream activity is always related to events recently experienced.

Stage 2

It is characterized by the person already sleeping, but not deeply. It lasts about five to fifteen minutes. The electroencephalogram shows slower wave frequencies, appearing the K complexes and sleep spindles. In this phase, awakenings by tactile stimulation, speech or body movements are more difficult than in the previous stage. Here the dream activity can already emerge in the form of a dream with an integrated history.