From: 「超自然心理學」書 /李察。韋斯曼 p.179

剛睡著時，是睡眠的第一階段，大腦仍十分活躍，處於高頻的α波。這段期間可能會出現兩種幻覺，分別是「入眠幻覺」與「將醒幻覺」，會有多種視覺現象，例如隨機斑點、明亮線條、幾何圖案、神祕動物、人類形體等，也常伴隨著奇怪的聲音，像是碰撞巨響、腳步聲、悄悄話、演講片段。這正是數百年來導致大家誤以為的撞鬼經驗。

這個階段之後，進入睡眠的第二階段，此時大腦仍不平靜，可能囈語連連，或激烈的說夢話，此階段大約持續20分鐘。然後逐漸進入第三階段，大腦和身體開始適度放鬆，經過20分鐘後，接著進入最深的睡眠階段(第四階段)，此時大腦活動最少，處於緩慢的δ波 (熟睡中)，可能發生尿床或夢遊。

第四階段約過了30分鐘後，會快速回溯睡眠的前三個階段，接著進入REM階段 (快速動眼期)，大腦展現類似第一階段的高頻率活動，心跳加快、呼吸變淺、全身無力感，此時正在作夢。每個人每晚都會經歷5次REM階段。(其實REM會隨著循環次數而增加，第一個REM只會持續幾秒鐘，在後面的循環則可能持續一個小時左右，整體平均REM約佔睡眠的1/4)

第一階段的幻覺混合REM的無力感，即形成所謂的「鬼壓床」，最簡單的解套方法，就只是：儘量動動手指或眨眼就行了。即使很小的動作，也能讓大腦從REM狀態切換到睡眠的第一階段，不久就可順利醒過來，安然回到現實。

Better Sleep 

Sleep has a profound impact on human health, improving attention, memory, emotional regulation and work performance, and reducing the risk of disease.

Today, most researchers describe sleep as occurring in two main phases: rapid-eye-movement (REM) sleep and non-REM sleep. Non-REM sleep comprises three stages, known as N1, N2 and N3, and these are characterized by specific brainwave patterns that reflect neural activity. These three stages of non-REM sleep plus REM sleep comprise the sleep cycle, and people who sleep well typically experience 4-6 cycles every night.

With multiple roles and thus at high risk of having bad sleep habits or lower quality of sleep due to the mental load of all those roles

As the person starts to go into a light sleep, or the N1 stage, those frequencies slow down into a pattern called theta waves. This stage typically lasts for 1-10 minutes.

During the second phase of sleep, N2, body temperatures drop, heart rates and breathing slow down and muscles relax. Brainwave frequencies now oscillate between slower waves and short bursts of neural activity. This phase generally lasts 10–25 minutes during the first sleep cycle, but gets progressively longer in later cycles, ultimately comprising about half of a person’s sleep time each night.

Slow-wave sleep occurs in the N3 stage, which is characterized by slow, high-amplitude waves called delta waves. This 20–40 minute phase makes up about one-quarter of a person’s sleep time. “When we think about what makes us feel good, this is the form of sleep that really does that,” says Wu. Some evidence suggests that slow-wave sleep plays a crucial part in restoring energy levels, repairing and growing tissues, clearing waste and boosting the immune system. Slow-wave sleep also aids learning and memory consolidation.

Neural activity picks up when the body enters REM sleep, which is when dreaming occurs. In this phase, which comprises one-quarter of sleep time each night, the brainwaves follow a beta-wave pattern. “You have mixed frequencies, so it looks like you’re awake,” Wu says. As the night progresses, the periods of slow-wave sleep shorten and REM sleep increases. REM sleep is important for cognitive functions, such as emotional regulation, memory and creative problem-solving.

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喝酒可更快入睡，但干擾睡眠品質

Avoids caffeine (caffeine can make it difficult to fall asleep and can affect the duration and intensity of slow-wave sleep) and bright lights at night to help improve the quality of his sleep. All exposure to light can suppress the secretion of melatonin, a hormone involved in regulating the body’s sleep–wake cycle, but exposure to blue light from electronic devices and energy-efficient lamps has the largest impact. Avoid taking naps, especially right before bedtime, because it can prevent them from feeling tired. Getting exercise is a great way to enhance sleep, but the timing matters, because the process of exercising releases hormones such as adrenaline (腎上腺素) and cortisol (皮質醇，會提高血壓、血糖水平和產生免疫抑制作用) that can keep people awake. Wu recommends that his patients do moderately strenuous exercise for 30–45 minutes a day, but not too close to bedtime.

Practising yoga nidra, an ancient method of inducing physical, mental and emotional relaxation, can help to improve the length of time spent asleep, as well as the efficiency and quality of the sleep in people with chronic insomnia.

Listening to music at bedtime can also help to improve the quality of sleep, especially for individuals with mild sleep problems. This might be because music helps to distract people from habits such as ruminating and hyperarousal. Audiobooks, however, don’t have the same effect. “It therefore seems possible that there are some peculiarly mysterious effects of music that science has yet to address.”