Piero Scaruffi

These are excerpts and elaborations from my book "The Nature of Consciousness"

The Adaptive Value Of Dreams The US neurobiologist Jonathan Winson expressed this concept in a more general way: dreams represent "practice sessions" in which animals (not only humans) refine their survival skills. REM sleep helps the brain to "remember" important facts without having to add cortical tissues. During REM sleep the brain (specifically, the hippocampus) processes information that accumulated during the day. In particular, during REM sleep the brain relates recent memories to old memories, and derives "tips" for future behavior. Dreams are a window on this "off-line processing" of information.  The neocortex processes sensory input and sends it to the hippocampus, which acts as a gateway to the limbic system. The limbic system mediates between sensory input and motor output. Winson used three main clues to reach his conclusions. 1. At birth, the hippocampus is needed to retrieve information stored in long-term memory, but, after about three years, the brain somehow learns how to access directly such information. 2. During REM sleep, the time when we dream, the neocortex is working normally, except that movement in the body is inhibited. 3. Most mammals, except for primates, exhibit a theta rhythm in the hippocampus (about six times per second) on only two occasions: whenever they perform survival-critical behavior, and during REM sleep.  Therefore, REM sleep must be involved in survival-critical behavior. Early mammals had to perform all their "reasoning" on the spot ("on-line"). In particular they had to integrate new information (sensory data) with old information (memories) immediately to work out their strategies. Winson speculates that at some point in evolution brains invented a way to "postpone" processing sensory information by taking advantage of the hippocampus: REM sleep. Theta rhythm is the pace at which that ("off-line") processing is carried out. Instead of taking input from the sensory system, the brain takes input from memory. Instead of directing action, the brain inhibits movement. But the kind of processing during REM sleep is the same as during the awake state. Winson speculates that this off-line processing is merging new information with old memories to produce strategies for future behavior. Theta rhythm disappeared in primates, but REM sleep remained as a fundamental process of brains. In humans, therefore, REM sleep, i.e. dreams, corresponds to an off-line process of integration of old information with new information. Dreaming is an accidental feature that lets us "see" some of the processing, although only some: a dream is not a story but a more or less blind processing of the day's experience. Winson goes as far as to suggest that all long-term memory may be constructed through this off-line process (i.e., during REM sleep): the hippocampus would process the day's events and store important information in long-term memory. There is a biologically relevant reason to dream: a dream is an ordered processing of memory that interprets experience that is precious for survival. Dreaming is essential to learning. Winson relates this off-line process that operates during sleep with Freud's subconscious. Freud was right that dreams are the bridge between the conscious and the unconscious, although that bridge is of a different nature. The Freudian "subconscious" becomes the phylogenetically-ancient mechanism involving REM sleep, in which memories and strategies are formed in the cortex. Similarly, Hobson thinks that the ultimate purpose of dreams is to populate long-term memory, to help us learn. We dream hypothetical situations so that we will be prepared to face real situations of the same kind. When a situation occurs during the day, it has probably already been played at least once at night in our dreams, and we know what to expect.  By dreaming, we train our brain: dreams are mental gymnastics.  It's like saying that, in order to see something, we must first create the vision of that something in our mind. In a sense, we dream what is worth remembering.   Back to the beginning of the chapter "Dreams" | Back to the index of all chapters