Studies carried out during the past 50 years, particularly those using recent neuroimaging techniques, show that the areas of the central nervous system that seem more active in REM sleep are found in the brain stem, in the limbic system, and in secondary, associative cortical areas, at variance with the alert waking state, during which the frontal lobes and the primary sensory and motor cortices are privileged. Thus, the stage of sleep in which dreaming has its greatest expression appears to be characterized by a prevalent orientation toward the inner world of memories and emotions. In line with this view, the adjective "paradoxical,'' as applied to the REM stage, may sound improper. Its physiological characteristics, in fact, appear perfectly orthodox if considered as an expression of a positive and qualitative shifting toward a greater resonance of the inner world—a shifting, however, that although paradigmatic for the REM state, may be available throughout the sleep and wake cycle.
As discussed earlier, a variety of findings encourage stepping beyond the Manichean barriers separating the states of wakefulness, REM sleep, and non-REM sleep in order to appreciate the continuity of the mind across these states. For instance, although it may be true that mentation during REM is largely bizarre, systematic demonstrations indicate that REM dream content also shows a heavy reliance on representations of familiar elements from the waking environment. By the same token, if it is true that during the awake state resources are usually employed in relating to the external environment, there are still opportunities for coding operations and processing of internal material. Consider, for instance, the fantasy activity conceived as ongoing information processing. As Jerome Singer states, ''the popular notion of a daydream represents only one manifestation of a more general class of phenomena perhaps best described as internally generated diversion from an ongoing motor or cognitive task.'' There is evidence that some type of coding and restructuring of long-term stored material goes on a great deal of the time while the organism is awake.
The critical point that needs further examination is the psychophysiological significance of this shifting. The first question is whether accessing and activating the previously mentioned brain areas in the REM stage—besides serving a possible, although not yet known, biological function—involves any direct functional value for the mind. Second, the problem arises of the semantic meaning of dream and dream-like mentation; as stated earlier, dreaming activity could in principle produce some objective organizational benefit to the mind, independently from the subjective experiencing of dreaming and from the content of the experienced dream, and that organizational benefit may be augmented by dream recall and interpretation.
An overview of the different positions on these issues shows that scholars in the broader field of dreaming can be divided into approximately two groups. On the one hand are those who, although not rejecting the adaptive hypothesis, from various angles and with different reasoning tend to characterize dream mentation as a degradation of the self-conscious, self-controlled thought of wakefulness. For example, sleep physiologist Giuseppe Moruzzi, while maintaining that sleep has a function coherent with the need to restore the myriad of cerebral neural networks, also believed dreaming to be the expression of an ''impoverished conscience.'' Taking into account the intense activity of the brain in REM sleep, he stated that ''the plastic debt accumulated during wakefulness could be paid while the cortical neurons continued to discharge impulses, even if in a different way than usual.'' Loss of consciousness could thus be the result not of a silence but of the temporary loss of a meaningful dialogue between nerve cells.
On the other hand, there are scholars who view REM sleep as a privileged theater for the type of plastic revision on which the adaptive flexibility of our central nervous system is based. In their view, accessing memory stores may set the potential for creating new associations, rearranging past patterns, and reformulating future plans in accord with experiences of the day. Rather than ''temporary loss of a meaningful dialogue,'' dreaming represents the ''temporary emergence of a differently meaningful dialogue.'' In such a perspective, at least some dreaming would be the expression of an alternative form of''intelligence,'' common to a variety of thinking modalities leaning toward the imagery and metaphoric side of the human vast symbolic capacity. A "symbolic-presentational" form of intelligence (Susanne Langer's terminology), although semantic and communicative, resists a complete narrative formulation when compared to the ''symbolic-representational'' intelligence that prevails in the vigilant waking state.
In 1890, William James stated: ''Our normal waking consciousness, rational consciousness as we call it, is but one special type of consciousness, whilst all about it, parted from it by the filmiest of screens, there lie potential forms of consciousness entirely different.'' Thus, even though the age-old dilemma of dreaming has been engaged by modern science, we still remain within the interpretational dualism that has characterized the history of thought on dreaming. The work carried out during the past 50 years, however, seems to justify a certain optimism with respect to a converging of views in the near future.
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