Dream Ontogeny

Dream Ontogeny
While the social aspects of dreaming offer insight into the socio-developmental benefits of dreams, so does an examination of the ontogeny of sleep and dreaming. Multiple facets of our mental development are ontogenetically scheduled (Bertenthal, 1996). For example, at about nine months of age it is apparent that infants acquire the new skill of treating others as intentional beings (Trevarthen, 1979). Other mental capacities also begin to develop within a predictable timeline, a universal characteristic of the human species and occurring independent of culture. Likewise, the architecture of sleep cycles follows a specific ontogeny that is consistent to humans as a species (Frank and Heller, 2003).
REM sleep occurs most frequently in newborns, and decreases throughout the lifespan. Newborns can spend about eight hours a day in REM sleep, and REM sleep actually occurs at sleep onset (Winson, 2002). In contrast, as we age, sleep onset is characterized by stages of NREM sleep, followed by REM sleep in less amounts. By the age of three, REM sleep is reduced to about three hours a day and continues to decline throughout the lifespan.
Why is REM sleep such a prominent brain state in the developing brain? One answer to this question follows from the previous argument as to the potential function of dreams, i.e., a virtual rehearsal mechanism. It is well known that children, and even other species, suffer detrimental effects when raised in impoverished environments (Joseph, 1999). The converse is also true. Infants raised in environments with rich amounts of information show increased cognitive skills at an earlier age, and this can even extend throughout the lifespan (Diamond, 1988); an enriched environment during the development of the nervous system optimizes its functionality.
As mentioned above, all evidence points toward the notion that virtual environmental stimuli are treated in essentially the same way as real stimuli from the environment. Therefore, it would make adaptive sense for an organism that is young and still developing to experience the most rich and vivid environment possible. If this is experienced in infant dreams, then this is exactly what has been selected for, as newborns spend a good deal of time in this virtual environment.
Of course, the virtual environment will likely be a reflection of the real environment and how infants interact with their virtual environment is going to be a function of the perceptual and cognitive capacities they have developed. So, the REM mentation of infants, which we are arguing constitutes a type of dreaming, probably consists of recreations with important sensory information that is taken in while awake. It is this information, and these interactions with the physical and social world, which is likely vital in shaping the future mental development of the child.
The brain connections that are thought to be developed during REM sleep are not going to be haphazardly put into place and subsequently strengthened, rather, through dreaming, these connections may be optimized based on experience. If mental rehearsal can induce change and lead to the reorganization of the brain in relatively short periods of time (Pascual-Leone et al., 1995), surely the cumulative time spent dreaming will impact brain development as well. While this argument may seem contradictory to data indicating that dreaming is a gradual cognitive process that does not take place regularly until around ages 5-9 (Foulkes, 1999), the dream experience is bound to be tightly coupled with the development of general mental abilities including perception, language, and memory. Further, the lack of verbal dream reports should not exclude, a priori, the possibility that a form of a dreaming is taking place.
Hypotheses can be generated based on the notion that infants have a type of dreaming mechanism, and this dreaming mechanism influences the development of certain cognitive abilities. Specifically, we predict that an optimal environment that has a good deal of complexity will interact with a healthy sleep schedule to cause an optimal development of intellectual capacities. Conversely, a disruption in the normal REM cycle of a developing individual could have negative consequences on the development of mental functions. An example of a disorder where this hypothesis could be investigated is autism. Autism has been likened to a TOM deficit and is associated with disrupted sleep patterns (Richdale and Prior, 1995). Based on the theory developed in this paper, it is predicted that a portion of the deficits observed in autistics is due to their lack of REM sleep. We theorize that through an inability to dream, the autistic brain is negatively affected and through this negative effect, so are subsequent behaviors, such as interactions with the world around them.