Along day of hard work and mental stress may diminish one’s vitality which can be only restored by a good night sleep. Having rested undisturbed, the body normally comes back to its normal state of energy, just as the dawn of a new day brings in fresh life and hope for all. However, everyone is not so lucky to have a peaceful, uninterrupted sleep night after night as many people suffer from sleep disorders and have a disturbed sleep pattern. Insomnia or lack of sleep also drains away the body’s energy and disrupts the sleep and wake time, thus making one feel quite sick.
As we trace the patterns of sleep, it is indeed astonishing that while we sleep, our brain buzzes with activity. This brain activity can be recorded as Electro Encephalograms (EEGs) which reveals the dynamic behaviour of sleep manifested as characteristic electrical patterns in a sleeping person’s brain as well as the presence or absence of eye movement. Based on this, the two main types of sleep are Rapid-Eye-Movement (REM) sleep and Non-Rapid-Eye-movement (NREM) sleep. On an EEG, REM sleep is called the active sleep that is characterized by low-amplitude high-frequency waves having ‘alpha’ rhythm. The eye movements of REM sleep are believed to be related to dreams, as people who are awakened from REM sleep normally report their dreams in a vivid manner.
On the other hand, in NREM sleep, there are three distinct stages: N1, N2, and N3. During the progression from stage N1 to N3, brain waves become slower and more synchronized. Therefore in stage N3, EEG reveals high-amplitude, low-frequency waves (delta waves) that is characteristic of deep sleep. Normally, in a healthy adult, sleep begins with NREM sleep where the transition from wakefulness to N1 occurs within seconds after the slow eye movements appear in a person who is feeling very sleepy. The second stage, or N2, comes next that lasts for 10 to 25 minutes, which then progresses to N3 stage. The latter is deep sleep that lasts for 20 to 40 minutes.
As NREM sleep progresses, the brain becomes less responsive to external stimuli, and it is difficult to awaken an individual from sleep. The REM sleep follows this, which comprises about 20 to 25 per cent of total sleep in a typical healthy adult. NREM sleep and REM sleep continue to alternate through the night in a cyclical fashion. Interestingly, most NREM sleep occurs in the first part of the night. Although the first episode of REM sleep may last only about five minutes, it generally becomes longer through the night. The normal cycles of NREM and REM sleep are believed to restore both physical and mental states of the body on waking up. Normally, younger people have more concentrated periods of deep sleep and older people have more periods of REM sleep. Sleep patterns can be affected by many factors like age, stress, alcohol, drugs, environmental conditions such as temperature and light, and time of the day or night relative to an individual’s internal/biological clock. Normally, the intake of coffee, tea, chocolate or cola drinks at bedtime interferes with sleep. Whereas, herbal oils such as juniper, lavender, geranium, sandalwood, neroli and ylang ylang help to induce sleep.
Stages of Sleep in Humans
What is the purpose of Dreams in sleep ?
Dreams are believed to be the expressions of deep-seated emotions that to some extent are precognition about the future. According to Sigmund Freud’s theory of dreams, dreams are a representation of unconscious desires, thoughts and motivations. The activation-synthesis model of dreaming, proposed by J. Allan Hobson and Robert MeClarley in 1977, emphasizes that certain neural circuits in the brain become activated during REM sleep, which is turn, activates specific areas of the limbic system involved in emotions, sensations and memories, including the amygdale and hippocampus. The brain’s interpretation of this neural activity during sleep is manifested as dreams. However, there are several other theories that provide suggestive explanations to the occurrence and meaning of dreams.
What are sleep disorders ?
Sleep disorders are changes in sleeping patterns, which may range from excessive daytime sleepiness and increased movement during sleep to difficulty in sleeping and abnormal sleep behaviors. Insomnia is the most common type of sleep disorder where a person is unable to get proper amount of sleep one needs to wake up refreshed. It, however, is often a symptom of another problem like stress, anxiety, depression, jet lag and intake of some drugs among other factors. In addition to insomnia, the most common sleep disorders are sleep Apnea, Restless Legs Syndrome (RLS), and narcolepsy. Respiration and sleep are strongly coupled. Changes in the neurological control of breathing are known to affect sleep patterns and this may result in periodic breathing, upper airway obstruction besides sleep Apnea periods.