Origins of Dreaming

To the Editor: Morton F. Reiser, M.D. (1), approached the topic of dreams in psychiatry by integrating the parallel findings of neurobiological, clinical, and psychoanalytical studies. He drew attention to the changes that have taken place in the regulation of wakefulness in the evolution from lower vertebrates to the mammalian species. In their explanation of the function of dream sleep, Crick and Mitchison (2) also drew attention to a change in brain organization in the evolutionary process. Because REM sleep appeared first in mammals, they suggested that a new type of REM-facilitating circuitry developed that became a prerequisite for dream sleep and made possible the unloading of useless experiences from the brain during dreaming, thereby consolidating meaningful memory imprints.

There is also another evolutionary aspect of the step from lower species to mammals that has relevance for understanding the origins of dreaming. Simultaneous to brain development, a fundamental change also occurred in the infant-mother relationship. The survival of the infant became dependent on the continuity of the mother’s feeding and the ensuing vital relationship. My colleagues and I (3) found that the feeding of the newborn is related to a significant increase in the amplitude of the infant’s brain activity in occipital-temporal-parietal areas. This suggests parallel activation of the projection areas of several sensory modalities, which become linked to the primitive experience of satisfaction induced by feeding. The hypothesis of the effect of infant feeding on primitive mental imagery seems thus to have a neurophysiological basis.

After feeding, the human infant is likely to fall asleep. The amplitude increase in occipital-temporal-parietal areas during feeding may activate the cortical junction of these areas, which Dr. Reiser suggested plays a gateway role in dreaming. This is another example of concurrent neurophysiological and experiential events, in which perceptual and primitive emotional processes contribute to sleep and the induction of dreaming. Such a process, involving neurobiology and infant-mother interaction, also makes sense of the isomorphic features common to REM physiology and psychoanalytic dream theory (4).

The Crick-Mitchison hypothesis fits well with Freud’s first postulate about the meaning of dreaming, namely, that dreams are guardians, i.e., preservers, of the restorative power of sleep but does not fit with the second postulate concerning the meaning of dream images. To understand the origin of the latter, it is necessary to also appreciate the evolutionary significance of the change in the infant-mother relationship and its impact on brain function.