Brain Waves And Eye Movements: Rem Sleep Measurement

Sleep is measured primarily by polysomnography (PSG), which is considered the gold standard for diagnosing sleep disorders. PSG reveals that sleep architecture has several distinct stages that vacillate between non-rapid eye movement (NREM) and rapid eye movement (REM) sleep. During REM sleep, the eyes twitch, and brain activity is similar to its activity when awake. Dreaming usually happens during REM sleep. REM sleep is important for memory and overall functioning.

REM sleep can be measured in several ways, including:

- Electroencephalogram (EEG): Measures brain waves.

- Electrooculography (EOG): Determines sleep patterns and how long one stays in the REM sleep stage.

- Electromyogram (EMG): Measures muscle function.

- Wearables: Devices worn on the body to detect sleep patterns, hygiene, and health. Common wearables include Fitbit, Garmin, and Apple Watch.

- Sleep diary: An easy and affordable way to track sleep quality, but may be unreliable and unable to measure sleep architecture.

- Wrist actigraphy: Detects accelerated motion and assesses sleep quality, but unable to accurately determine the sleep stage.

Polysomnography (PSG)

During a PSG study, several non-invasive sensors are attached to the patient to record multiple physiological signals. This typically includes electroencephalography (EEG) to measure brain activity, electrooculography (EOG) to record eye movements, and electromyography (EMG) to measure muscle activity, particularly from the chin or legs. Additionally, PSG may also involve monitoring other parameters such as electrocardiography (ECG) for heart activity, respiratory effort sensors, and measurement of blood oxygen levels.

The data collected during PSG is then analysed to identify the different stages of sleep. REM sleep is characterised by rapid eye movements, increased brain activity resembling wakefulness, and muscle atonia. PSG allows for the identification of the onset of REM sleep, its duration, and the number of eye movements during this stage. These parameters are important in understanding sleep quality and can provide insights into various sleep disorders and their potential treatments.

PSG is particularly useful in the diagnosis and management of sleep disorders such as obstructive sleep apnea, narcolepsy, and REM sleep behaviour disorder. It helps in differentiating between sleep stages and determining the presence of abnormal sleep patterns. By analysing the recorded signals, sleep specialists can identify disruptions in the sleep cycle and develop appropriate treatment plans to improve sleep quality and overall health.

While PSG is the gold standard for measuring REM sleep, there are also other methods available, such as wearable devices and sleep diaries, which can provide insights into sleep patterns and help track sleep habits over time. However, these methods may not offer the same level of detail and accuracy as PSG.

Electroencephalogram (EEG)

During REM sleep, the brain is highly active, and this increased brain activity is reflected in the EEG readings. The EEG will show different patterns of brain waves during REM sleep compared to non-REM sleep, allowing for the identification and analysis of this unique stage of sleep.

In a clinical setting, an EEG typically involves placing electrodes on the scalp to detect and record the electrical activity of the brain. This non-invasive procedure provides valuable data about brain function during sleep, including the identification of distinct sleep stages such as REM sleep.

EEG technology has advanced significantly over the years, and modern EEG devices have become more portable and accessible for at-home use. These advancements have made it possible for individuals to measure their brain waves and track their sleep patterns from the comfort of their own homes.

In addition to EEG, other methods used to measure REM sleep include electrooculography (EOG), which tracks eye movements, and electromyography (EMG), which measures muscle activity. These techniques provide complementary information to EEG data, contributing to a comprehensive understanding of sleep architecture and the unique characteristics of REM sleep.

Electrooculography (EOG)

EOG is one of the tools used in sleep studies, which are the gold standard for diagnosing sleep disorders. Sleep studies use sensors to record eye movements and brain activity, which are used to classify sleep phases and stages. Sleep studies can help diagnose conditions like sleep apnea and other sleep disorders.

EOG is also used in conjunction with other methods to measure REM sleep. Electroencephalography (EEG) measures brain waves, electromyography (EMG) measures muscle function, and EOG measures eye movements. These methods are used together to measure REM sleep and determine sleep architecture, or the various sleep stages a person experiences throughout the night.

EOG can also be used at home with an in-home EEG device. This requires wearing a headband while sleeping to detect the signals transmitted throughout the brain and body. This method can be used to determine the various sleep stages a person experiences, including REM sleep.

Electromyogram (EMG)

During REM sleep, the body's skeletal muscles become disabled, except for those needed for eye movement and breathing. This is what allows people to remain still while they dream. An EMG can detect this loss of muscle tone by measuring electrical activity in the muscles during sleep.

In addition to an EMG, a polysomnogram also uses an electroencephalogram (EEG) to record brain waves, and an electrooculogram (EOG) to measure eye movements. Together, these tools help sleep specialists determine the quality and length of a person's REM sleep.

While a polysomnogram is considered the most reliable way to measure REM sleep, there are also wearable devices that can provide insights into sleep patterns. These include the Fitbit, Garmin, and Apple Watch. However, these devices have limited functionality and are not designed to replace clinical sleep studies.

Wearables

While wearables are easily accessible, affordable, and widely used, there is limited data available on their validity, accuracy, and reliability in measuring sleep parameters. They are not as accurate as lab tests, such as polysomnography, which is considered the gold standard for sleep tracking. However, wearables can still be useful for monitoring basic sleep metrics, such as time spent asleep and time awake.

When interpreting more detailed sleep metrics, such as deep sleep and rapid eye movement (REM) sleep, it is important to focus on the trend rather than the specific number, as the accuracy of wearables in measuring these stages is less reliable. The bias in the data obtained from wearables can vary, and it is not yet clear if this bias is constant. Therefore, it is essential to correlate the data with other related metrics and, more importantly, how you feel.

Overall, wearables can provide valuable insights into your sleep habits and help you make informed decisions to improve your sleep quality. However, it is important to remember that they should not be used as a substitute for professional medical advice, especially if you are experiencing sleep problems.

Frequently asked questions