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The stages of sleep can be separated into two categories: non-rapid eye movement (NREM) and rapid eye movement (REM).
NREM is further divided into four stages of sleep increasing in depth and intensity: Stage 1 NREM, Stage 2 NREM, Stage 3 NREM and Stage 4 NREM.Stages 3 and 4 together make up what’s called Slow Wave Sleep (SWS). Slow Wave Sleep is characterized by slow undulating brain waves originating from the cerebral cortex
REM is the stage of sleep associated with dreaming, it’s characterized by lateral movement of the eyes. The brain becomes much more active than the NREM phases of sleep.
While sleeping, your brain goes through each stage of sleep beginning at NREM-1, then to NREM-2, NREM-3, NREM-4 and finally to REM sleep. One cycle of sleep generally takes around 90 minutes to complete.
Lets take a closer look at each individual stage of sleep:
Stage 1 NREM
This is the most shallow stage of sleep, and as a result, we may be awaken easily. Our eyes also slowly roll back in their sockets during this stage as well. During sleep onset many people experience vivid hallucinations, not unlike dreaming, this phenomenon is called hypnogogic hallucinations.
Stage 2 NREM
Our brain waves slow down, resulting in a lower frequency but higher amplitude measurement. Stage 2 NREM sleep is characterized by K-complexes and sleep spindles which have unknown origins and functions. K-complexes are termed as such because they would look like the letter ‘K’ if stretched out. The appearance of K-complexes could be due to the brain suppressing itself to maintain sleep. Sleep spindles are a rapid burst of activity that lasts about one to two seconds before returning to normal activity.
Our core body temperature experiences a drop during Stage 2 NREM
[Learn how to read a polysomnograph here]
Stage 3 NREM
In this stage, Delta waves begin to emerge, which are characterized by slow (low frequency) and large (high amplitude) brain waves. Stage 3 and 4 together make up Slow Wave Sleep (SWS). Stage 3 can be considered a transition between light and deep sleep.
Stage 4 NREM
The final and deepest stage of NREM sleep, the brain continuously registers low-frequency, high-amplitude delta waves. These delta waves indicate that massive regions of the brain are giving the same signal, this type of activity can be compared to everybody in a classroom chanting in harmony, creating a large, synchronous signal.
[Learn how to read a polysomnograph here]
REM sleep
Dreaming occurs during REM (Rapid Eye Movement) sleep, during REM sleep, the eyes dart back and forth laterally, the brain becomes very active and registers high frequency, low amplitude waves accordingly.
[Learn how to read a polysomnograph here]
As you can see from the comparable polysomnographs, the brain doesn’t look much different in REM than it does while awake. The EMG is a flat line indicating complete paralysis of the body, preventing us from acting out our dreams.
NREM is further divided into four stages of sleep increasing in depth and intensity: Stage 1 NREM, Stage 2 NREM, Stage 3 NREM and Stage 4 NREM.Stages 3 and 4 together make up what’s called Slow Wave Sleep (SWS). Slow Wave Sleep is characterized by slow undulating brain waves originating from the cerebral cortex
REM is the stage of sleep associated with dreaming, it’s characterized by lateral movement of the eyes. The brain becomes much more active than the NREM phases of sleep.
While sleeping, your brain goes through each stage of sleep beginning at NREM-1, then to NREM-2, NREM-3, NREM-4 and finally to REM sleep. One cycle of sleep generally takes around 90 minutes to complete.
Lets take a closer look at each individual stage of sleep:
Stage 1 NREM
This is the most shallow stage of sleep, and as a result, we may be awaken easily. Our eyes also slowly roll back in their sockets during this stage as well. During sleep onset many people experience vivid hallucinations, not unlike dreaming, this phenomenon is called hypnogogic hallucinations.
Stage 2 NREM
Our brain waves slow down, resulting in a lower frequency but higher amplitude measurement. Stage 2 NREM sleep is characterized by K-complexes and sleep spindles which have unknown origins and functions. K-complexes are termed as such because they would look like the letter ‘K’ if stretched out. The appearance of K-complexes could be due to the brain suppressing itself to maintain sleep. Sleep spindles are a rapid burst of activity that lasts about one to two seconds before returning to normal activity.
Our core body temperature experiences a drop during Stage 2 NREM
[Learn how to read a polysomnograph here]
Stage 3 NREM
In this stage, Delta waves begin to emerge, which are characterized by slow (low frequency) and large (high amplitude) brain waves. Stage 3 and 4 together make up Slow Wave Sleep (SWS). Stage 3 can be considered a transition between light and deep sleep.
Stage 4 NREM
The final and deepest stage of NREM sleep, the brain continuously registers low-frequency, high-amplitude delta waves. These delta waves indicate that massive regions of the brain are giving the same signal, this type of activity can be compared to everybody in a classroom chanting in harmony, creating a large, synchronous signal.
[Learn how to read a polysomnograph here]
REM sleep
Dreaming occurs during REM (Rapid Eye Movement) sleep, during REM sleep, the eyes dart back and forth laterally, the brain becomes very active and registers high frequency, low amplitude waves accordingly.
[Learn how to read a polysomnograph here]
As you can see from the comparable polysomnographs, the brain doesn’t look much different in REM than it does while awake. The EMG is a flat line indicating complete paralysis of the body, preventing us from acting out our dreams.
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