Why don’t we remember our dreams in the morning?

02.05.2023.

We dream every night and our brain constructs approximately 4.8 hours of dreams during an average night’s sleep. In most cases, however, we cannot recall them after waking up. According to Péter Simor and his fellow researchers, there is a physiological explanation for this. Forgetting enables our brain to prepare for the tasks awaiting us after waking up.

While the special, often bizarre nature, the emotional overtones, and the perceived or real meaning of dreams have been one of the greatest mysteries of mankind for thousands of years, dream research is a rather overlooked area in psychology and neuroscience. It does not belong to the popular topics even within the field of sleep science. To fill this void, Péter Simor (ELTE Faculty of Education and Psychology), Róbert Bódizs (Semmelweis University), and Philippe Peigneux (Free University of Brussels) dedicated their recently published article to the question of dreaming and dream amnesia, that is, how difficult it is to remember our dreams. In their scientific work, they argue that dreaming is not a mental by-product of sleep but it is directly connected to its basic functions.

The homeostatic functions of sleep maintaining the internal balance of the body have been confirmed by numerous research data and today it is considered a fact that they play an essential role in restoring the brain functions that get “worn out” during wakefulness. The scientists refer to the restorative processes carrying out the “tasks” accumulated during the period preceding sleep as the reactive homeostatic functions of sleep. These fundamental physiological processes, including the mechanisms serving the stability and optimal functioning of the nervous and immune systems, take place during the first few hours of sleep, when we spend a lot of time in deep sleep. In contrast, the so-called predictive homeostasis, during which the body prepares for expected environmental changes in advance, takes place in the second half of sleep. There is considerably less information about this period of sleep, which is mostly spent in the REM phase and shallow NREM sleep.

According to the authors of the study, the role of early morning sleep can be captured by these predictive homeostatic processes that serve as preparation for the future. They believe that tuning in to the future – that is, wakefulness after sleep – is another major function of sleep. In other words,

we not only “sleep on it”, but sleep also prepares us for the coming day.

Dreaming is also part of this process, which, as a kind of transitional state between sleep and wakefulness, can be interpreted as the mental simulation of future scenarios. However, because night dreams unfold relatively loosely, less fettered by the constraints of reality, specific, well-defined goals activated during awakening effectively inhibit and erase these dream memories. Additionally, recalling the dream would make it difficult to imagine future goals. This means that we also forget our dreams so that we could focus on the future as easily as possible in the morning, the researchers pointed out.

The original article is available on the site Neuroscience & Biobehavioral Reviews.

Source: ELTE PPK