Vivid dreaming occurs in which stage of sleep?
A. Stage I non-REM
B. Rapid eye movement (REM) stage
C. Stage II non-REM
D. Delta stage
Correct Answer: B. Rapid eye movement (REM) stage
Other characteristics of rapid eye movement (REM) sleep are deep sleep (the patient cannot be awakened easily), depressed muscle tone, and possibly irregular heart and respiratory rates. This is the stage associated with dreaming. Interestingly, the EEG is similar to an awake individual, but the skeletal muscles are atonic and without movement. The exception is the eye and diaphragmatic breathing muscles, which remain active. The breathing rate is altered though, being more erratic and irregular. This stage usually starts 90 minutes after falling asleep, and each of the REM cycles gets longer throughout the night. The first period typically lasts 10 minutes, and the final one can last up to an hour.
Option A: Non-REM sleep is a deep, restful sleep without dreaming. This is the lightest stage of sleep and starts when more than 50% of the alpha waves are replaced with low-amplitude mixed-frequency (LAMF) activity. There is muscle tone present in the skeletal muscle and breathing tends to occur at a regular rate. This stage tends to last 1 to 5 minutes, consisting of around 5% of the total cycle.
Option C: This stage represents deeper sleep the heart rate and body temperature drop. It is characterized by the presence of sleep spindles, K-complexes, or both. These sleep spindles will activate the superior temporal gyri, anterior cingulate, insular cortices, and the thalamus. The K-complexes show a transition into a deeper sleep. Stage 2 sleep lasts around 25 minutes in the initial cycle and lengthens with each successive cycle, eventually consisting of about 50% of total sleep.
Option D: Delta stage, or slow-wave sleep, occurs during non-REM Stages III and IV and is often equated with quiet sleep. This is considered the deepest stage of sleep and is characterized by a much slower frequency with high amplitude signals known as delta waves. This stage is the most difficult to awaken from, and for some people, even loud noises (over 100 decibels) will not awaken them. As people get older, they tend to spend less time in this slow, delta wave sleep and more time stage N2 sleep. This is the stage when the body repairs and regrows its tissues, builds bone and muscle, and strengthens the immune system.