Do octopuses show wake-like skin patterns and brain activity while sleeping?

Details

Researchers combined behavioural observations, computer analysis of skin patterns and electrical recordings from the central brain to examine two sleep stages in octopuses. Quiet sleep was periodically interrupted by roughly 60-second bouts of pronounced body movements and rapid changes in skin patterns and texture.

During these bouts, the animals were harder to arouse, although they could wake rapidly. The bouts were also regulated according to sleep need. Together, these findings supported identifying them as a distinct active sleep stage rather than simply waking movements.

Active sleep included varied skin patterns shared across the octopuses and strongly resembling waking patterns. Brain electrical activity also resembled waking activity, with the strongest signals in connected regions associated with learning and memory. During quiet sleep, those regions were relatively silent but produced rhythmic signals resembling mammalian sleep spindles—brief bursts of rhythmic brain activity—in frequency and duration.

These similarities suggest that some features of two-stage sleep may have evolved independently in octopuses and vertebrates. They do not establish identical sleep states or reveal whether octopuses experience dreams. The abstract does not specify the species or number of animals studied.