This is when a person is fully awake.
- Beta activity/desynchronized EEG

Waking stage

A stage of sleep which shows small amplitude, fast EEG waves, no postural tension, and rapid eye movements. The waves of REM sleep closely resembles that of waking. 
- Nightmare

Rapid-eye-movement sleep (REM sleep)

A stage of sleep without rapid eye movements which divide into stages 1, 2, and 3 sleep (NREM 1, 2, 3).
- Stage 1
- Stage 2
- Stage 3

Non-REM (NREM sleep)

This is when a person is relaxed. People are usually getting ready to sleep during this stage and have their eyes closed, but they do not enter the drowsiness stage yet.
- Alpha rhythm

Relaxing stage

- Waking
- Relaxing
- Rapid-eye-movement sleep (REM sleep)
- Non-REM (NREM sleep)

University of Rochester

Throughout sleep, there are different stages characterized by the presence or absence of types of brain waves. Typically, we cycle through these stages 4-5 times a night, sleeping on average 7-8 hours. These stages are broken down into two categories:

- Non-REM
- REM

Sleep Stages

Breedlove, S. & Watson, N. (2017). Behavioral neuroscience, eighth edition. Oxford University Press.

Behavioral Neuroscience 8th Edition

- Electroencephalography (EEG)
- Electro-oculography (EOG)
- Electromyography (EMG)

Analysis of human sleep

Stages of human sleep

REM sleep is a phase of sleep distinguished by the rapid movement of the eyes. Brain wave activity during this stage closely resembles that of an awake person, and it is the period when most dreaming takes place. A key feature of REM sleep is the paralysis of the body's voluntary muscle systems, although muscles essential for circulation and respiration remain active. This combination of high brain activity and lack of muscle tone is why REM sleep is often called 'paradoxical sleep'. Additionally, this sleep stage is understood to be involved in processes of learning and memory.

Rapid Eye Movement (REM) Sleep

Analyze the following three distinct observations from a sleep study. For each observation, identify the specific sleep stage or category it represents and justify your answer by referencing the key characteristics described.

Identifying Sleep Stages from Observations

A person is awakened by their alarm clock and reports having been in the middle of a very vivid, bizarre dream. For a brief moment after waking, they feel unable to move their arms or legs. Which of the following best explains the physiological state they were likely in just before waking?

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