Researchers determine connection between daily sleep rhythm and long-term memory

Sleep in adulthood is linked to specific times of day. In contrast, sleep in early life lacks this clear daily (circadian) pattern. It is not yet known how this development-related change is controlled. Prof Dr Andreas Thum, head of the Genetics working group at the Institute of Biology at Leipzig University, together with a team of researchers from the University of Pennsylvania, has determined exactly when the so-called circadian sleep pattern begins in young fruit fly larvae (Drosophila).

This happens through the formation of a new brain connection between cells that encode time in the brain (the internal clock) and cells that promote arousal. The daily sleep rhythm helps the fly larvae to achieve deeper sleep, which enables the formation of long-term memory. These new findings, which were recently published in the renowned journal „Science Advances“, could also be important for research into the sleep behaviour of human infants.

In this study, in which the researchers from the University of Pennsylvania played a leading role, the scientists from the University of Leipzig identified the precise point in development at which the circadian clock begins to control sleep in the fruit fly. This leads to the development of sleep rhythms in the early third larval stage. „In the study, we were able for the first time to combine our expertise – the learning behaviour of the larva and the necessary brain circuits – with the field of sleep research in the fruit fly“, explains Professor Thum. For human infants, too, the maturation of sleep patterns is important for cognitive development. In the beginning, infants often have to alternate between sleeping and feeding, which restricts longer deep sleep phases. With increasing age, infants can endure longer periods without food, which enables deeper sleep periods and more complex brain functions, says the biologist.

Thum and his colleagues were able to show that fruit flies develop a long-term memory for unpleasant stimuli in the early third larval stage. This memory depends on the onset of deep sleep, which begins as soon as circadian sleep rhythms occur. Our hypothesis is that the development of circadian sleep enables more complex cognitive processes, including the formation of long-lasting memories,

News from "Universität Leipzig" dated 12 September 2023