![]() Regarding the link between dreaming and neurophysiology, 60 years of debates has been necessary to get rid of the rapid eye movement (REM) sleep hypothesis of dreaming, and it is now acknowledged by a majority of dream researchers, be they neuroscientist or not, that REM sleep is neither necessary nor sufficient to get a dream report and that dream reports can be obtained at the awakening of any sleep stage ( 2, 7, 9– 12). After awakening, dreams may be recalled due to the recollection-often fleeting-of the dream memory. Importantly, oneiric representations can be bizarre. In other words, most of the time dreams are experienced as real, and the dreamer is unaware of being asleep except in the peculiar case of lucid dreaming ( 8). The dreamer is therefore both the unaware creator of the dream and its conscious observer and often actor” ( 7). It is composed of “virtual” sensory perceptions and of emotions and it can evoke various and complex representations of the setting, characters, objects and circumstances. The following phenomenological one is nonetheless shared and used by numerous dream researchers : “Dreaming is a spontaneous phenomenon during sleep which is a true phenomenal experience, i.e., it feels as an experience of the waking life (loss of reality testing). This mysterious and ubiquitous phenomenon is however difficult to investigate with an experimental approach, since researchers can access dreams only indirectly and a posteriori via dream reports possibly truncated by partial memory and transformed by the awake mind ( 3).Īs a consequence, the definition of dreaming is still under debate ( 4, 5). Introductionĭreaming is an experience shared by everyone very few people report having never dreamt. Decrease of intra-sleep awakenings due to taking psychotropic drugs is the variable, which most correlates with dream recall frequency. The influence of psychotropic drugs on REM sleep does not modify their impact on dream recall frequency. Sedative psychotropic drugs reduce dream recall frequency by improving sleep quality, but their impact on dream content is not well-known. Dream content tends to improve in parallel to improvements in symptoms of depression. Most antidepressants reduce dream recall frequency. ![]() DRF is nonetheless influenced by several other factors (e.g., interest in dreams, the method of awakening, and personality traits), which may explain a large part of the variability of results observed and cited in this article. Indeed, molecules that improve sleep continuity by reducing intra-sleep awakenings also reduce the frequency of dream recall, which is coherent with the “arousal-retrieval model” stating that nighttime awakenings enable dreams to be encoded into long-term memory and therefore facilitate dream recall. The reduction of intra-sleep awakenings seems to be the parameter explaining best the modulation of DRF by psychotropic drugs. Importantly, the impact of psychotropic drugs on rapid eye movement (REM) sleep does not explain DRF modulations. Few occurrences of nightmare frequency increase have been reported, with intake of molecules disturbing sleep or with the withdrawal of some psychotropic drugs. For sedative psychotropic drugs, their improvement of sleep quality is associated with a reduction of DRF, but the effect on dream content is less clear. For antidepressant drugs, in the great majority, they reduce dream recall frequency (DRF), and the improvement of depressive symptoms is associated with an increase of positive emotion in dream content. A review of the few existing experimental results on the topic leads us to the following conclusions. Over the past 60 years, the impact of psychotropic drugs on dream recall and content has been scarcely explored. Lyon Neuroscience Research Center, CNRS UMR 5292 - INSERM U1028 - Lyon 1 University, Lyon, France.
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