300-million-year-old brain rhythm links humans, birds, and lizards

A recent study has uncovered that the infraslow brain rhythm—a very slow neural oscillation previously thought to be unique to mammals and closely tied to deep, non-REM sleep—is also present in reptiles and birds. By recording brain activity in seven lizard species using a novel, miniature biologger device developed with nanotechnology experts, researchers demonstrated that this rhythm, cycling over tens of seconds, is a conserved feature across these diverse groups. The rhythm not only involves neuronal activity but also encompasses physiological processes such as heart rate, breathing, and blood flow, indicating it is a global, organism-wide phenomenon. This discovery pushes back the evolutionary origin of this brain rhythm to over 300 million years ago, predating the emergence of mammals. The findings challenge previous assumptions about the evolution of sleep states, suggesting that key aspects of sleep architecture, including the infraslow rhythm linked to non-REM sleep, were inherited from a common ancestor of reptiles, birds, and mammals rather than evolving independently in mammals. The