Sleep is a behavioural state characterised by the temporary suspension of the state of watchful consciousness. The particular subjective nature of sleep has always stimulated philosophical thought, but the actual behaviour of the sleeping organism has also attracted wide interest across all cultures.

From a human point of view, the subjective state of consciousness linking us to our real surroundings disappears when we sleep, while a state of consciousness known as oneiric appears when we dream. The oneiric experience is not always remembered, or remembered only in part, when we awake from sleep. From an objective point of view, a reduction in our reactions to stimuli from our surroundings is a characteristic of a sleeping person.

It is especially worth remembering that sleep was the subject of in-depth studies in the field of the figurative arts well before scientific research into its mechanisms began. Just as the interaction between graphic arts and anatomy proved to be very useful, so the works of painters and sculptors depicting sleep over various periods of history have been equally important. Some of these works of art show the different stages of sleep (NREM and REM), which correspond perfectly to those identified by modern scientific research.

NREM Sleep characterised by motory rest, reduced and regular circolatory and respiratory activity, oneiric activity

Fig. 2: Giorgione. "Sleeping Venus". (Credit: Staatliche Kunstsammlungen, Dresda)