No abstract

Breathing is irregular during rapid eye-movement (REM) sleep, whereas it is stable during non-REM sleep. Why this is so remains a mystery. We propose that irregular breathing has a cortical origin and reflects the mental content of dreams, which often accompany REM sleep. We tested 21 patients with narcolepsy who had the exceptional ability to lucid dream in REM sleep, a condition in which one is conscious of dreaming during the dream and can signal lucidity with an ocular code. Sleep and respiration were monitored during multiple naps. Participants were instructed to modify their dream scenario so that it involved vocalizations or an apnoea, -two behaviours that require a cortical control of ventilation when executed during wakefulness. Most participants (86%) were able to signal lucidity in at least one nap. In 50% of the lucid naps, we found a clear congruence between the dream report (e.g., diving under water) and the observed respiratory behaviour (e.g., central apnoea) and, in several cases, a preparatory breath before the respiratory behaviour. This suggests that the cortico-subcortical networks involved in voluntary respiratory movements are preserved during REM sleep and that breathing irregularities during this stage have a cortical/subcortical origin that reflects dream content.

Patients with sleepwalking episodes or sleep terrors (SW/ST) exhibit sudden abnormal behaviours arising from sleep, mostly from N3 sleep (American Academy of Sleep Medicine, 2014). Patients usually open their eyes, look around with a confused gaze, sit, stand, walk, talk, scream or flee their bed (Derry, Harvey, Walker, Duncan, & Berkovic, 2009). There is a continuum between the different behavioural patterns of arousal parasomnias. Specifically, the behavioural patterns of non-rapid eye movement (NREM) parasomnias appear with a hierarchical order, with arousal behaviours being the fundamental component, possibly followed by abnormal agitated conduct, which can be further accompanied by distressed emotional manifestations (Derry et al., 2009). Several clinical, polygraphical and brain functional imaging studies support the concept that these behaviours occur during local (primarily thalamo-amygdalo-cingulo-cortical) arousals from N3 sleep, disengaged from the control of the prefrontal and frontal associative cortex

In addition, the Discussion section contained an error, where, "For example, among 6 healthy lucid dreamers, who had been trained in lucid dreaming for several years, only one subject was able to perform the requested task and the ocular code after 3 full nights in a fMRI 36 " now reads: "For example, among 6 healthy lucid dreamers, who had been trained in lucid dreaming for several years, only one subject was able to perform the requested task and the ocular code after 3 full nights in an fMRI scanner 36. " These errors have now been corrected in the HTML and PDF versions of this Article.