Neuronal correlates of time integration into memories

Abstract

The circadian clock affects a wide range of physiological processes. Of particular interest is the influence of the clock on memory performance, as circadian dysfunction is associated with age- and disease-related decline in memory. In various species it has been shown that memory performance is regulated by the circadian clock. However, the anatomical and functional connection of the circadian clock and memory neurons has not been described in detail so far. This study now identifies that Diuretic hormone 31 (DH31)-positive clock neurons of the DN1p cluster regulate memory performance. DH31, a functional homolog of the mammalian calcitonin gene-related peptide, plays a crucial role in this process as a clock communication signal. DH31 facilitates memory performance during the night via indirect signalling, while DH31 signals directly to the mushroom bodies restricting memory performance specifically in the evening. This pleiotropic action of DH31 suggests that the circadian clock confines memory performance to a physiological dynamic range.