An introductory text at the top reads, Sleep. Looking in on a sleep study, you’ll see that the brain is actually very active during sleep, cycling through non-REM stages and ending in REM sleep approximately five times during the night. Transitions between stages are clearly visible as shifts in E E G patterns.
Graphs illustrating the human sleep cycle typically present an 8-hour time span, as shown below. But this doesn’t tell the whole story of sleep. The amount of time spent sleeping and content of our sleep changes across the life span. Only two thirds of U S adults get the recommended minimum of 7 hours per night.
A photo shows a woman wearing an electrode covered cap along with electrodes attached to her face and a graphical screen beside her that shows brain waves during the awake time in seconds. Text below read this sleep study participant wears electrodes that will measure her brain waves and body movements during sleep.
An illustration shows a waveform exhibiting two distinct wave patterns; the first part has equal peaks and troughs and wavelength whereas the second part, labeled Sleep, has a distorted waveform with irregular peaks and troughs with a shorter average wavelength. Text below reads, looking at brain waves allows us to trace a person’s stage of sleep. Here, we can see a clear shift from waking to sleeping patterns.
Two graphs are shown below of which the First graph depicts human sleep stages. The graph plots the hours of sleep on the horizontal axis and sleep stages on the vertical axis and their corresponding waves. Hours of sleep ranges from 0 to 8 in increments of 1. The data from the graph are as follows:
Awake: The stage occurs between 0 hour and 15 minutes and 7 hours 50 minutes and 8 hours. The corresponding brain wave is labeled alpha and beta waves in which the waves are non-linear and have slightly varied, short to moderate wavelengths.
REM sleep: The stage occurs between 1 hour 50 minutes and 2 hours, 3 hours 15 minutes and 3 hour 45 minutes, 4 hours 40 minutes and 5 hours 20 minutes, 6 hours and 6 hours 40 minutes, 7 hours 15 minutes and 7 hours 50 minutes. Between 6 hours and 6 hours 40 minutes the REM duration increases. The corresponding brain wave has low peaks and troughs and moderate wavelengths with one instance of a high peak and deep trough. The latter half of REM sleep is labeled eye movement phase and shows a consistent higher peaks and lower troughs.
Stage N 1: The stage occurs between 15 minutes and 20 minutes, 3 hours 30 minutes and 3 hours 45 minutes, 5 hours 20 minutes and 5 hours 30 minutes, 6 hours 40 minutes and 6 hours 50 minutes, 7 hours 10 minutes and 7 hours 15 minutes. The stage N 1 also occurs at 3 hour 15 minute, 4 hours 40 minutes, and 6 hours. The corresponding brain wave is labeled theta waves which has low peaks and troughs and short wavelengths.
Stage N 2: The stage occurs between 20 minutes and 30 minutes, 1 hour 30 minutes and 1 hour 40 minutes, 1 hour 50 minutes and 2 hour 5 minutes, 3 hour 5 minutes and 3 hours 15 minutes, 3 hours 45 minutes and 4 hours, 4 hours 30 minutes and 4 hours 40 minutes, 5 hour 30 minutes and 6 hour, and 6 hours 50 minutes and 7 hours 10 minutes. The corresponding wave is labeled theta waves in which there occurs tight wavelengths with occasional moderate peaks and troughs. The rapidly fluctuating waves in the first half of the stage are labeled sleep spindle and the long wavelength extreme peak and trough toward the end of the stage is labeled K-complex.
Stage N 3: The stage occurs between 30 minutes and 1 hour 30 minutes, 2 hours 5 minutes and 3 hours 5 minutes, and 4 hours and 4 hours 30 minutes while sleeping. And after 4 hours 30 minutes the stage N3 vanishes. There are two brain waves labeled delta waves (characterize slow wave sleep) in which one wave has longer wavelengths with occasional plateaus and the other has shorter wavelengths with higher peaks and lower troughs.
Text beside the graph reads, a typical night’s sleep has 4 or 5 multistage sleep cycles, each lasting approximately 90 minutes. Each cycle includes at least 1 non-REM and 1 REM stage. Pattern and duration of stages differ over the course of the night.
Second graph plots hours of sleep on the vertical axis against age in years on the horizontal axis.
The hours range from 0 to 24 in increments of 4 and age in years ranges from 0 to 90 in increments of 2 till 10 and from 20 to 90 in increments of 10. The region within (0, 0) to (0, 8), (20, 0) to (20, 7), and (90, 0) to (90, 4) is labeled non-REM sleep. The region within (0, 8) to (0, 16) and (90, 4) to (90, 6) is labeled REM sleep. Text reads, REM is 50 percent of total sleep time at birth. REM decreases to 20 percent of total sleep by age 85. The region within (0, 16) to (0, 24) and (90, 6) to (90, 24) is labeled walking.
All data are approximate.