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Olfaction-Related Factors Affecting Chemosensory Dream Content in a Sleep Laboratory.

Lenka Martinec Nováková, Monika Kliková, Eva Miletínová, Jitka Bušková

Brain Sciences September 16, 2021 DOI: 10.3390/brainsci11091225 (opens in new tab)

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Characteristics Experimental sleep-laboratory study with within-subject odour exposure and control conditions Peer reviewed
Sample size 60
Population Pre-screened healthy young adults
Interventions Vanillin Thioglycolic acid Odourless control condition
Duration Three nights at weekly intervals; first night adaptation, second and third nights with balanced odour exposure or control; dream reports collected after the first REM stage occurring after 3 a.m. and shortly before getting up
Topics Dreaming
Keywords Smell Recall Expectancy Dream Chemoreception Rapid eye movement Odour identification Odour awareness Mental sleep experience
Key findings All-night exposure to vanillin or thioglycolic acid, participants' appraisal of the ambient odour, and olfactory acuity did not affect reports of chemosensory dream content. Chemosensory dream content was more frequent in individuals with greater odour awareness. The authors suggest this may have implications for treatment when such dream experiences become unwanted or bothersome.

Abstract

Mental activity in sleep often involves visual and auditory content. Chemosensory (olfactory and gustatory) experiences are less common and underexplored. The aim of the study was to identify olfaction-related factors that may affect the occurrence of chemosensory dream content. Specifically, we investigated the effects of all-night exposure to an ambient odour, participants' appraisal of their current olfactory environment, their general propensity to notice odours and act on them (i.e., odour awareness), and their olfactory acuity. Sixty pre-screened healthy young adults underwent olfactory assessment, completed a measure of odour awareness, and spent three nights in weekly intervals in a sleep laboratory. The purpose of the first visit was to adapt to the experimental setting. On the second visit, half of them were exposed to the smell of vanillin or thioglycolic acid and the other half to an odourless control condition. On the third visit, they received control or stimulation in a balanced order. On each visit, data were collected twice: once from the first rapid eye movement (REM) stage that occurred after 3 a.m., and then shortly before getting up, usually from a non-REM stage. Participants were asked to report the presence of sensory dream content and to assess their current olfactory environment. Neither exposure, nor participants' assessments of the ambient odour, or olfactory acuity affected reports of chemosensory dream content but they were more frequent in individuals with greater odour awareness. This finding may have implications for treatment when such experiences become unwanted or bothersome.

Comparable studies

Other experimental studies on dreaming, most cited first.

Study Year Design Participants
Lucid Dreaming Verified by Volitional Communication during Rem Sleep Selected subjects proficient in lucid dreaming 1981 Experimental study n = 5
Incorporation of concern- and nonconcern-related verbal stimuli into dream content. Seven male subjects studied during sleep Stages 2 and REM 1981 Experimental study n = 7
Lucid Dreaming and Alpha Activity: A Preliminary Report Good dream recallers 1982 Experimental study n = 10
Lucid dreaming during NREM sleep: Two case reports 2012 Sleep laboratory study
The Dream Catcher experiment: blinded analyses failed to detect markers of dreaming consciousness in EEG spectral power. Human participants during sleep 2020 Experimental study with blinded classification n = 9

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