Experiencing Previous Dreams
Our memory systems may preserve most of our dreams.
Posted Feb 07, 2019
Do our dreams constitute an ongoing second life for each of us? I have argued that dreams have their own continuing storylines, characters, and scenes, and that these things are retained in dream-specific, cumulative memory stores such that dreamers can return to a dream scene over and over again. Many dreamers report gradual changes in the landscapes and scenery they encounter each time they revisit a scene, as if the dream world is evolving along with the dreamer. We are also slightly different in these dream worlds from our waking selves. We have a different set of goals, relationships, and histories than in our waking lives. Note that these dream selves are not mere wish fulfillments of our waking consciousness. These dream selves are not always heroic or exceptional in any way.
To my knowledge, there is no data-based or experimental evidence for cumulative dream memory stores that can be tied to the dream world specifically rather than to waking consciousness. For example, we often remember dreams in our waking lives, so it would not be surprising if those memories of dreams would build up over time and constitute some kind of dream-related memory system. However, what I am referring to is not a dream-related memory system, but a dream-specific cumulative memory store that is not easily accessible via waking consciousness. Its normal route of entry is via a dream state. But again, until now all we had was subjective reports of dreamers that these alternate dream worlds existed and were a reliable part of their dream lives.
In an interesting recent report, Curot et al. produced some evidence that could be interpreted to support the idea that dream-specific memory systems exist. Curot et al. discussed seven of their own cases of and an additional 35 cases from the literature of something they call “déjà-rêvé” (“already dreamed”). They used electrical brain stimulation techniques in patients with epilepsy to explore the production of déjà-rêvé experiences. They found that déjà-rêvé experiences occurred, though rarely, after stimulation deep to the right-sided medial temporal lobes. Examples: “I saw something — a dream, a nightmare I had a couple years ago. An object on a table.” Another patient evaluated in our epilepsy center said exactly at the moment of EBS in the entorhinal cortex: “I had the reminiscence of a dream I had few a days ago […] Well, I was like in a closed room […] It was very fleeting. I felt the atmosphere of the room […] I saw a color, an orange color.”
It's hard to say exactly what these déjà-rêvé experiences tell us about dreaming or the anatomy of dreaming. On the face of it, déjà-rêvé provides direct evidence for the fact that some people claim to recall dreams that they once had, but had been lost to conscious memory systems. Déjà-rêvé dreams are indirect support for the idea that dream-specific memory systems may exist.
If specific memory systems exist, then we have to ask why human nature requires an ongoing dream life that apparently has no clear connection to waking life. Why are there two lives within each one of us?
In your dream life, you are growing, changing, and pursuing goals and desires just as you are in your waking life, but with significant differences. Sometimes the dream life seems impoverished relative to the waking life, and vice versa. But the two lives seem not to interact in any obvious way. In some pre-modern cultures, people could identify with their dream selves rather than their waking selves. They gave greater ontological weight to the dream world than we do. But it is difficult to understand how they could do so for long periods of time and still function effectively in waking life. Nevertheless, the ethnographic reports of these dream-centered societies are clear that the dream world was taken quite seriously and considered quite real.
Curot, J. Luc Valton, L., Denuelle, M., Vignal, J-P., Maillard, L., Pariente, J., Trébuchon, A., Bartolomei, F., and Barbeaub, E.J. (2018). Déjà-rêvé: Prior dreams induced by direct electrical brain stimulation. Brain Stimul. 2018 Jul-Aug; 11(4): 875–885. doi: 10.1016/j.brs.2018.02.016: 10.1016/j.brs.2018.02.016