A natural and periodic state of physical rest, characterized by a lessening, or temporary and near shut- down, of the five senses.
While the body rests in a state of sleep, the spirit withdraws and is active, with only the silver cord to maintain the link between the two. During this state, the spirit freely roams in aspects of the spirit world. Unfortunately, the brain being smaller, cannot record the experiences of spirit which is outside the realm of our time and sense dimensions. The sleep state is part of the natural function by which the spirit body is released, and for some, to familiarize itself with the world of spirit and to prepare for its future habitation.
The degree of spirit which can be reached is dependent upon the state of the soul evolution. All can travel in spirit, but some are limited in their range. Some people travel in sleep to the darker spheres of the spirit world, either because that corresponds with their own soul-state or because it is the action of their own free will as they desire to be used in service.
Although it is possible to train the brain to remember visits to the spirit world, very few people do this. Those who find it easiest to remember are those who would make the best mental mediums.
Spirit beings have no need for sleep, but they do have periods of rest and relaxation whenever they feel the need.