THE SLEEPING BRAIN

To talk about dreaming it is necessary first to understand the process of sleeping, as the onieric dream is an event that occurs during sleep.

About a third of life is spent asleep, during which time the brain remains active in generating dreams, which provide us with some of the most intense and strange experiences that we have.

Science has a number of explanations of why we need to sleep. One is that of “down time” for the body to repair itself. Another is that the brain needs to switch off from the outside world in order to sort, process, and memorize information obtained during the day. This vision of sleep as a process to repair and rest for the brain was dominant until 1945. In 1950 Giuseppi Moruzzi discovered that tonic activity of the reticular formation of the brain is kept active by sensorial information, it keeps the forebrain activated, and when this activity is reduced in the reticular formation it provokes sleep. Another discovery showed that it is the reticular formation, more exactly the pons, which produced the action of sleeping, and it is the part immediately above the pons that keeps the person awake. Sleep is thus an activity of the reticular formation and the neurons that pass through there.

The neurological information works in the human body through electric impulses, stimulated and modulated by neurotransmitters and hormones. In the movie, the Nerve Impulse, it is possible to watch this process.

Also in 1950, Nathaniel Kleitman discovered the sleep isn’t a single homogeneous process. Sleep is divided into phases. The first one identified was the REM, so-called because of rapid eyes movements, and the remainder of sleep has no fast eyes movements, and is therefore called non-REM. These two phases alternate cyclically following an organized pattern, as is shown in figure 1. This discovery showed clearly that “sleep” had a greater level of organization as a brain state than was previously thought. All these processes, both waking up and sleeping, and every other sub phase is a part of what is called the “circadian rhythm”, a rhythm that cycles approximately every 24 hours.

This rhythm is endogenous, although environmental clues of light and dark, hunger and thirst, and physiological activities can modulate it. Different organic systems have their own rhythm. We have a brain structure that modulates these, acting like a pacemaker. The names and processes are complex and need not concern us here. What is important is to understand that the brain has vital structures that control the process of sleep and waking. The pacemaker for instance is called the suprachiasmatic nucleus and is part of the anterior hypothalamus.

The Criteria That Set-up Sleep

Sleep is defined behaviorally by four criteria:

1) reduced motor activity.

2) decreased response to stimulation.

3) stereotypical postures (in human beings it is with the body lying and eyes closed).

4) relatively easy reversibility (very different from coma or hibernation).

OP 3 - DREAMING IN ACTION

SUPPORT EVIDENCE: Neurobiology of Sleep and Dreaming

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