For the purpose of learning how to sleep, the relationship between the higher control (cerebral cortex) and the lower control (sleep centre) must be made clear. Many studies, including animal experiments, have attempted to demonstrate the existence of a sleep centre. The exact location of this is still controversial, although it is believed to be located somewhere in the brain stem.
This is a few animal experiments that may be helpful in establishing the model of how sleep is controlled. The following animal experiments were conducted to demonstrate that the higher control (the cerebral cortex) has an arousal effect on the lower control (the sleep centre):
(1) If the sleep centre is stimulated electrically, the animal goes into sleep.
(2) If electrical stimulation is applied to the cerebral cortex of a sleeping animal, the animal wakes up. The cerebral cortex has relayed this stimulation to the sleep centre and this has an arousal effect.
(3) If a surgical cut is made in the mid-brain separating the connection between the cerebral cortex and the sleep centre, the animal goes into chronic sleep. Even if the cerebral cortex is now stimulated electrically, the sleep centre is no longer influenced and the sleeping animal cannot be aroused.
Hence the reason why we are sometimes awake for many hours in bed is that the thinking part of the brain—the cerebral cortex— is sending arousal messages to the sleep centre. The higher control has taken over and is preventing the sleep centre from switching into sleep; this is the commonest cause of insomnia.
To facilitate sleep we have to stop the cerebral cortex from sending arousal messages to the sleep centre, so that the latter can take over and trigger sleep. Arousal messages are uncontrolled thoughts. If we can learn how to control thoughts, we can shift from the waking mode to the transitional hypnotic state (THS) and consequently into sleep.
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