Invertebrate brains as diversified models for understanding sleep mechanisms and function.

Sleep is a widespread biological state found across both vertebrates and invertebrates, yet its expression and functions remain incompletely understood. Comparative research shows that invertebrates, including insects, exhibit behavioral and neurophysiological features that parallel vertebrate sleep, such as immobility, increased arousal thresholds, homeostatic rebound, and state-dependent neural activity. Insects combine compact nervous systems with well-characterized learning behaviors, making them powerful models for uncovering the mechanisms and functions of sleep. Here, we review sleep in insects with a focus on Apis mellifera and new data on polyphasic sleep patterns revealed by automated video analyses of antennal movement over day-long experimental periods. By comparing invertebrate and vertebrate sleep, we highlight both conserved and divergent features that inform hypotheses about sleep's adaptive roles in memory consolidation, energy regulation, and behavioral architecture. These insights underscore the value of invertebrate models for advancing comparative neuroscience and for inspiring computational approaches to challenges such as catastrophic forgetting in artificial neural networks.