L’artiste Abraham Poincheval (AP) s’est enfermé, pendant huit jours et sept nuits, dans une sculpture métallique reproduisant son corps en position assise et regardant une œuvre de Hans Hartung au travers d’un système de cône placé devant ses yeux. Son sommeil et sa température ont été enregistrés en continu grâce à une polysomnographie et à un capteur-capsule avalé oralement enregistrant sa température interne toutes les 2min. Il a dormi en moyenne 355,1min par 24 heures réparties en sommeil lent léger (47,1min de N1 et 192,2min de N2), sommeil lent profond (100,4min de N3) et avec seulement 4,3 % de sommeil paradoxal (15,4min). Le sommeil, bien qu’à prédominance nocturne était fractionné par périodes de 20min au plus. Le sommeil profond a donc remarquablement résisté aux conditions d’inconfort de la situation alors que le sommeil paradoxal a été très altéré, ne durant que quelques courtes minutes et suivi d’un réveil rapide. La position d’AP dans la sculpture explique sans doute cela car elle ne lui permettait pas de soutenir sa tête, donc le sommeil paradoxal, avec son atonie musculaire caractéristique, était impossible à maintenir longtemps. Le minimum thermique s’est situé entre 5 h 17 et 6 h 35 du matin. L’amplitude de la température centrale a baissé de plus de 30 % entre le début et la fin du protocole. Malgré l’immobilité et la situation de confinement extrême, il n’y a pas eu de désynchronisation des rythmes circadiens. En conditions de sommeil physiquement contraignantes et inconfortables, le sommeil profond a été maintenu alors que le sommeil paradoxal s’est effondré. Sur le plan homéostasique, cela signifie que sur un laps de temps court, en situation de survie, la récupération par le sommeil lent profond pourrait l’emporter sur le sommeil paradoxal.

Sleep in extreme situations has been little studied. The artist Abraham Poincheval (AP) is known for his performances in confined spaces. For his show at the Perrotin Gallery in Paris, he was enclosed for 8days and 7nights in a metal sculpture of his body in a seated position, with his head facing a work by Hans Hartung at the end of a cone system placed in front of his eyes which occluded all other visual stimuli. The interior of the metal structure was not padded and there was no head support. His sleep and internal temperature were continuously recorded using polysomnography (Grael, Compumedics) and an orally swallowed temperature sensitive capsule (Bodycap) with temperature sampling every 2min. AP slept an average of 355.1min/24h, composed of light slow-wave sleep (N1: 47.1min, N2: 192.2min), deep slow-wave sleep (N3: 100.4min), and REM sleep 4,3 % (15.4min). Sleep, although mostly nocturnal, was split into periods of no more than 20min. Deep sleep was therefore remarkably resistant to the uncomfortable experimental conditions, while REM sleep was markedly impaired, lasting only a few short minutes and followed by rapid awakening. This is probably due to the head position within the sculpture which was unsupported, so REM sleep with its inherent muscle atonia led to involuntary head flexion and was impossible to sustain for long. The thermal minimum was between 5:17 a.m. and 6:35 a.m. The amplitude of the core temperature decreased by more than 30 % between the beginning and the end of the protocol. Despite the immobility induced by the confined experimental conditions, there was no desynchronization of circadian rhythms. The sleep time was surprisingly long given the conditions, and slow-wave sleep was relatively preserved with an amount typically found in normal subjects while REM sleep was markedly impaired. Slow-wave sleep is clearly preserved underlying its central role in physical and mental homeostasis. REM sleep is clearly more fragile. The reduction in REM sleep linked to position has been found in a study of sleep in the sitting position in airplanes where loss of muscle tonus in the neck fragments REM sleep. Techniques for selective REM sleep deprivation also use muscle atonia: one of the initial techniques of selective REM sleep deprivation relied on muscle atonia in REM causing a cat to fall from a small perch into water. In man, the lack of head support is clearly a source of REM fragmentation. However in the case of this study, we cannot exclude an effect of other factors, notably the meditative techniques used by the performer to maintain attention on the painting, described as a dream state punctuated by visual hallucinations. Surprisingly, despite physical isolation within the sculpture, AP's biological rhythms remained stable. However, the conditions were not those of complete isolation: noise, the presence of the public in the gallery who occasionally talked to AP through the sculpture, and variations in light during the day were all temporal cues. In addition, a heatwave during the performance raised the temperature in the room with reduced total sleep time on the hottest night. Although the phase of the circadian rhythm measured by the internal temperature did not change, the amplitude fell which is compatible with reduced physical activity. In conclusion, under physically constraining and uncomfortable sleep conditions, deep sleep is maintained while REM sleep is starkly reduced. From a homeostatic point of view, this means that over a short period of time, in a survival situation, energy recovery through deep slow-wave sleep takes priority over REM sleep.