I have heard that monatics in many cases sleep as little as 4-5 hours per night. In what way do they train, to reduce the amount of sleep needed for nightly restitution?
Are there methods of training to remain (increasingly) mindful while sleeping?
Once the practitioner attains certain level of mastery in meditation and mindfulness, their sleep acquires a character of meditation. It's not like they don't sleep at all, but they do retain certain level of deep awareness during their sleep.
Specifically, when they see a dream, they know it's a dream. They remain aware of their body lying down on the bed. They remain aware of the content of their consciousness no matter how disjointed it gets during a deep sleep. If something happens around them, they wake up easily to provide their help if needed.
From my personal experience I can say this has gotten increasingly true for me over the years of practice.
As far as specific methods, stopping internal dialogue and mental gossip really helps mindfulness.
I heard about monks that are mindful when they are sleeping but those monks are higly trained.to reduce the number of you sleep,you could increase the length of time you do sitting meditation.people sleep because they want rest and re_energise.in meditation body can rest and re_energise.so longer you do sitting meditation,less sleep you need.
Dreaming is one of the 6 bardos or liminal states in Tibetan Buddhism. There complete list is
In the Tibetan tradition it is possible to work with the dream bardo by practicing dream yoga. It is linked to lucid dreaming but brings a lot more to it. It is perfectly possible to train yourself to lucid dream and I know a few people that have - so it seems very reasonable that advanced practitioners could work with and extend this technique.
I believe the point here relates to meditation and the monastic life. We (lay people) deal with so many problems and so many distractions that our minds are overstimulated, more important than that, we don't practice a lot of meditation, therefore our minds require a lot of time to rest, this is easy for one to see, when you are anxious you don't sleep well.
A monk deals with problems and distractions too, but I believe not as many, not with the intensity we deal living in a big city. They study a lot, keep the monastery running, give dhammatalks etc... but the level of stress is different in such activities, also they practice a lot of meditation, so their mind is usually more sharp, calm and focused, requiring less time to rest.
In Tibetan buddhism there are a set of practices calles the six yogas of Naropa. They are specially important in the Karma Kagyu School of Tibetan Buddhism. One of these yogas is called the Dream Yoga and its purpose is to develop awareness during your dreaming time. The masters of this meditation never lose counciousness. When they go to sleep the know they are falling sleep. Later they recognize that they are sleeping without dreams. Then they recognize their dreams and are able to modify them as they wish. Finally the wake up are are able to remember everything that happened during their sleeping time. To do the six yogas of Naropa you need advance training and be in retreat. Usually you are required to do at least one meditation retreat that lasts three years, three months, three weeks and three days. You definitely need a teacher, this is not something you can learn by reading. Best luck in your meditations.
An Arahat does not sleep like a normal person. He may give rest to the body but in doing so is fully aware hence not asleep. This is a natural consequence of reducing impurities of the mind.
Even if you are not an Arahat, Vipassana Meditation will make remove impurities of the mind so you will need less sleep. There is no special training to reduce sleep or be aware during sleep other than regular Vipassana Meditation. If your mind falls into Bhavanga then you cannot be aware or mindful or have the right type of attention.
Another enemy is laziness, drowsiness. All night you slept soundly, and yet when you sit to meditate, you feel very sleepy. This sleepiness is caused by your mental impurities, which would be driven out by the practice of Vipassana, and which therefore try to stop you from meditating. You must fight to prevent this enemy from overpowering you. Breathe slightly hard, or else get up, sprinkle cold water on your eyes, or walk a little, and then sit again.
Similarly, when you go to bed at night, close your eyes and feel sensation anywhere within the body. If you fall asleep with this awareness, naturally as soon as you wake up in the morning, you will be aware of sensation. Perhaps you may not sleep soundly, or you may even remain fully awake throughout the night. This is wonderful, provided you stay lying in bed and maintain awareness and equanimity. The body will receive the rest it needs, and there is no greater rest for the mind than to remain aware and equanimous. However, if you start worrying that you are developing insomnia, then you will generate tensions, and will feel exhausted the next day. Nor should you forcefully try to stay awake, remaining in a seated posture all night; that would be going to an extreme. If sleep comes, very good; sleep. If sleep does not come, allow the body to rest by remaining in a recumbent position, and allow the mind to rest by remaining aware and equanimous.
Source: The Discourse Summaries by S.N. Goenka
Also see: Suppati Sutta